@article{WaltherGuanterHeimetal.2018, author = {Walther, Sophia and Guanter, Luis and Heim, Birgit and Jung, Martin and Duveiller, Gregory and Wolanin, Aleksandra and Sachs, Torsten}, title = {Assessing the dynamics of vegetation productivity in circumpolar regions with different satellite indicators of greenness and photosynthesis}, series = {Biogeosciences}, volume = {15}, journal = {Biogeosciences}, number = {20}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1726-4170}, doi = {10.5194/bg-15-6221-2018}, pages = {6221 -- 6256}, year = {2018}, abstract = {High-latitude treeless ecosystems represent spatially highly heterogeneous landscapes with small net carbon fluxes and a short growing season. Reliable observations and process understanding are critical for projections of the carbon balance of the climate-sensitive tundra. Space-borne remote sensing is the only tool to obtain spatially continuous and temporally resolved information on vegetation greenness and activity in remote circumpolar areas. However, confounding effects from persistent clouds, low sun elevation angles, numerous lakes, widespread surface inundation, and the sparseness of the vegetation render it highly challenging. Here, we conduct an extensive analysis of the timing of peak vegetation productivity as shown by satellite observations of complementary indicators of plant greenness and photosynthesis. We choose to focus on productivity during the peak of the growing season, as it importantly affects the total annual carbon uptake. The suite of indicators are as follows: (1) MODIS-based vegetation indices (VIs) as proxies for the fraction of incident photosynthetically active radiation (PAR) that is absorbed (fPAR), (2) VIs combined with estimates of PAR as a proxy of the total absorbed radiation (APAR), (3) sun-induced chlorophyll fluorescence (SIF) serving as a proxy for photosynthesis, (4) vegetation optical depth (VOD), indicative of total water content and (5) empirically upscaled modelled gross primary productivity (GPP). Averaged over the pan-Arctic we find a clear order of the annual peak as APAR <= GPP < SIF < VIs/VOD. SIF as an indicator of photosynthesis is maximised around the time of highest annual temperatures. The modelled GPP peaks at a similar time to APAR. The time lag of the annual peak between APAR and instantaneous SIF fluxes indicates that the SIF data do contain information on light-use efficiency of tundra vegetation, but further detailed studies are necessary to verify this. Delayed peak greenness compared to peak photosynthesis is consistently found across years and land-cover classes. A particularly late peak of the normalised difference vegetation index (NDVI) in regions with very small seasonality in greenness and a high amount of lakes probably originates from artefacts. Given the very short growing season in circumpolar areas, the average time difference in maximum annual photosynthetic activity and greenness or growth of 3 to 25 days (depending on the data sets chosen) is important and needs to be considered when using satellite observations as drivers in vegetation models.}, language = {en} } @article{KabothBahrBahrZeedenetal.2021, author = {Kaboth-Bahr, Stefanie and Bahr, Andr{\´e} and Zeeden, Christian and Yamoah, Kweku A. and Lone, Mahjoor Ahmad and Chuang, Chih-Kai and L{\"o}wemark, Ludvig and Wei, Kuo-Yen}, title = {A tale of shifting relations}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, publisher = {Macmillan Publishers Limited, part of Springer Nature}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-021-85444-7}, pages = {10}, year = {2021}, abstract = {Understanding the dynamics between the East Asian summer (EASM) and winter monsoon (EAWM) is needed to predict their variability under future global warming scenarios. Here, we investigate the relationship between EASM and EAWM as well as the mechanisms driving their variability during the last 10,000 years by stacking marine and terrestrial (non-speleothem) proxy records from the East Asian realm. This provides a regional and proxy independent signal for both monsoonal systems. The respective signal was subsequently analysed using a linear regression model. We find that the phase relationship between EASM and EAWM is not time-constant and significantly depends on orbital configuration changes. In addition, changes in the Atlantic Meridional Overturning circulation, Arctic sea-ice coverage, El Ni{\~n}o-Southern Oscillation and Sun Spot numbers contributed to millennial scale changes in the EASM and EAWM during the Holocene. We also argue that the bulk signal of monsoonal activity captured by the stacked non-speleothem proxy records supports the previously argued bias of speleothem climatic archives to moisture source changes and/or seasonality.}, language = {en} } @article{PourteauSchererSchornetal.2019, author = {Pourteau, Amaury and Scherer, Erik E. and Schorn, Simon and Bast, Rebecca and Schmidt, Alexander and Ebert, Lisa}, title = {Thermal evolution of an ancient subduction interface revealed by Lu-Hf garnet geochronology, Halilbagi Complex (Anatolia)}, series = {Geoscience Frontiers}, volume = {10}, journal = {Geoscience Frontiers}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1674-9871}, doi = {10.1016/j.gsf.2018.03.004}, pages = {127 -- 148}, year = {2019}, abstract = {The thermal structure of subduction zones exerts a major influence on deep-seated mechanical and chemical processes controlling arc magmatism, seismicity, and global element cycles. Accretionary complexes exposed inland may comprise tectonic blocks with contrasting pressure-temperature (P-T) histories, making it possible to investigate the dynamics and thermal evolution of former subduction interfaces. With this aim, we present new Lu-Hf geochronological results for mafic rocks of the Halilbagi Complex (Anatolia) that evolved along different thermal gradients. Samples include a lawsonite-epidote blueschist, a lawsonite-epidote eclogite, and an epidote eclogite (all with counter-clockwise P-T paths), a prograde lawsonite blueschist with a "hairpin"-type P-T path, and a garnet amphibolite from the overlying sub-ophiolitic metamorphic sole. Equilibrium phase diagrams suggest that the garnet amphibolite formed at similar to 0.6-0.7 GPa and 800-850 degrees C, whereas the prograde lawsonite blueschist records burial from 2.1 GPa and 420 degrees C to 2.6 GPa and 520 degrees C. Well-defined Lu-Hf isochrons were obtained for the epidote eclogite (92.38 +/- 0.22 Ma) and the lawsonite-epidote blueschist (90.19 +/- 0.54 Ma), suggesting rapid garnet growth. The lawsonite-epidote eclogite (87.30 +/- 0.39 Ma) and the prograde lawsonite blueschist (ca. 86 Ma) are younger, whereas the garnet amphibolite (104.5 +/- 3.5 Ma) is older. Our data reveal a consistent trend of progressively decreasing geothermal gradient from granulite-facies conditions at similar to 104 Ma to the epidote-eclogite facies around 92 Ma, and the lawsonite blueschist-facies between 90 Ma and 86 Ma. Three Lu-Hf garnet dates (between 92 Ma and 87 Ma) weighted toward the growth of post-peak rims (as indicated by Lu distribution in garnet) suggest that the HP/LT rocks were exhumed continuously and not episodically. We infer that HP/LT metamorphic rocks within the Halilbagi Complex were subjected to continuous return flow, with "warm" rocks being exhumed during the tectonic burial of "cold" ones. Our results, combined with regional geological constraints, allow us to speculate that subduction started at a transform fault near a mid-oceanic spreading centre. Following its formation, this ancient subduction interface evolved thermally over more than 15 Myr, most likely as a result of heat dissipation rather than crustal underplating. (C) 2018, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V.}, language = {en} } @article{Herzschuh2019, author = {Herzschuh, Ulrike}, title = {Legacy of the Last Glacial on the present-day distribution of deciduous versus evergreen boreal forests}, series = {Global ecology and biogeography : a journal of macroecology}, volume = {29}, journal = {Global ecology and biogeography : a journal of macroecology}, number = {2}, publisher = {John Wiley \& Sons, Inc.}, address = {Hoboken}, issn = {1466-822X}, doi = {10.1111/geb.13018}, pages = {198 -- 206}, year = {2019}, abstract = {Issue Despite their rather similar climatic conditions, eastern Eurasia and northern North America are largely covered by different plant functional types (deciduous or evergreen boreal forest) composed of larch or pine, spruce and fir, respectively. I propose that these deciduous and evergreen boreal forests represent alternative quasi-stable states, triggered by their different northern tree refugia that reflect the different environmental conditions experienced during the Last Glacial. Evidence This view is supported by palaeoecological and environmental evidence. Once established, Asian larch forests are likely to have stabilized through a complex vegetation-fire-permafrost soil-climate feedback system. Conclusion With respect to future forest developments, this implies that Asian larch forests are likely to be governed by long-term trajectories and are therefore largely resistant to natural climate variability on time-scales shorter than millennia. The effects of regional human impact and anthropogenic global warming might, however, cause certain stability thresholds to be crossed, meaning that irreversible transitions occur and resulting in marked consequences for ecosystem services on these human-relevant time-scales.}, language = {en} } @article{EngelsMedeirosAxfordetal.2020, author = {Engels, Stefan and Medeiros, Andrew S. and Axford, Yarrow and Brooks, Steve and Heiri, Oliver and Luoto, Tomi P. and Nazarova, Larisa B. and Porinchu, David F. and Quinlan, Roberto and Self, Angela E.}, title = {Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity}, series = {Global change biology}, volume = {26}, journal = {Global change biology}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/gcb.14862}, pages = {1155 -- 1169}, year = {2020}, abstract = {Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a metadata analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric data sets overall consisting of 837 lakes. Our results indicate that in most of our data sets, summer temperature (T-jul) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing T-jul in regions with present-day T-jul between 2.5 and 14 degrees C. In some areas with T-jul > 14 degrees C, chironomid diversity stabilizes or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (similar to 15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites.}, language = {en} } @article{SublettSendulaLamadridetal.2019, author = {Sublett, David Matthew and Sendula, Eszter and Lamadrid, Hector and Steele-MacInnis, Matthew and Spiekermann, Georg and Burruss, Robert C. and Bodnar, Robert J.}, title = {Shift in the Raman symmetric stretching band of N-2, CO2, and CH4 as a function of temperature, pressure, and density}, series = {Journal of Raman spectroscopy : JRS}, volume = {51}, journal = {Journal of Raman spectroscopy : JRS}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {0377-0486}, doi = {10.1002/jrs.5805}, pages = {555 -- 568}, year = {2019}, abstract = {The Raman spectra of pure N-2, CO2, and CH4 were analyzed over the range 10 to 500 bars and from -160 degrees C to 200 degrees C (N-2), 22 degrees C to 350 degrees C (CO2), and -100 degrees C to 450 degrees C (CH4). At constant temperature, Raman peak position, including the more intense CO2 peak (nu+), decreases (shifts to lower wave number) with increasing pressure for all three gases over the entire pressure and temperature (PT) range studied. At constant pressure, the peak position for CO2 and CH4 increases (shifts to higher wave number) with increasing temperature over the entire PT range studied. In contrast, N-2 first shows an increase in peak position with increasing temperature at constant pressure, followed by a decrease in peak position with increasing temperature. The inflection temperature at which the trend reverses for N-2 is located between 0 degrees C and 50 degrees C at pressures above similar to 50 bars and is pressure dependent. Below similar to 50 bars, the inflection temperature was observed as low as -120 degrees C. The shifts in Raman peak positions with PT are related to relative density changes, which reflect changes in intermolecular attraction and repulsion. A conceptual model relating the Raman spectral properties of N-2, CO2, and CH4 to relative density (volume) changes and attractive and repulsive forces is presented here. Additionally, reduced temperature-dependent densimeters and barometers are presented for each pure component over the respective PT ranges. The Raman spectral behavior of the pure gases as a function of temperature and pressure is assessed to provide a framework for understanding the behavior of each component in multicomponent N-2-CO2-CH4 gas systems in a future study.}, language = {en} } @article{FiedlerHainzlZoelleretal.2018, author = {Fiedler, Bernhard and Hainzl, Sebastian and Z{\"o}ller, Gert and Holschneider, Matthias}, title = {Detection of Gutenberg-Richter b-Value Changes in Earthquake Time Series}, series = {Bulletin of the Seismological Society of America}, volume = {108}, journal = {Bulletin of the Seismological Society of America}, number = {5A}, publisher = {Seismological Society of America}, address = {Albany}, issn = {0037-1106}, doi = {10.1785/0120180091}, pages = {2778 -- 2787}, year = {2018}, abstract = {The Gutenberg-Richter relation for earthquake magnitudes is the most famous empirical law in seismology. It states that the frequency of earthquake magnitudes follows an exponential distribution; this has been found to be a robust feature of seismicity above the completeness magnitude, and it is independent of whether global, regional, or local seismicity is analyzed. However, the exponent b of the distribution varies significantly in space and time, which is important for process understanding and seismic hazard assessment; this is particularly true because of the fact that the Gutenberg-Richter b-value acts as a proxy for the stress state and quantifies the ratio of large-to-small earthquakes. In our work, we focus on the automatic detection of statistically significant temporal changes of the b-value in seismicity data. In our approach, we use Bayes factors for model selection and estimate multiple change-points of the frequency-magnitude distribution in time. The method is first applied to synthetic data, showing its capability to detect change-points as function of the size of the sample and the b-value contrast. Finally, we apply this approach to examples of observational data sets for which b-value changes have previously been stated. Our analysis of foreshock and after-shock sequences related to mainshocks, as well as earthquake swarms, shows that only a portion of the b-value changes is statistically significant.}, language = {en} } @article{TapeJonesArpetal.2018, author = {Tape, Ken D. and Jones, Benjamin M. and Arp, Christopher D. and Nitze, Ingmar and Grosse, Guido}, title = {Tundra be dammed}, series = {Global change biology}, volume = {24}, journal = {Global change biology}, number = {10}, publisher = {Wiley}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/gcb.14332}, pages = {4478 -- 4488}, year = {2018}, abstract = {Increasing air temperatures are changing the arctic tundra biome. Permafrost is thawing, snow duration is decreasing, shrub vegetation is proliferating, and boreal wildlife is encroaching. Here we present evidence of the recent range expansion of North American beaver (Castor canadensis) into the Arctic, and consider how this ecosystem engineer might reshape the landscape, biodiversity, and ecosystem processes. We developed a remote sensing approach that maps formation and disappearance of ponds associated with beaver activity. Since 1999, 56 new beaver pond complexes were identified, indicating that beavers are colonizing a predominantly tundra region (18,293km(2)) of northwest Alaska. It is unclear how improved tundra stream habitat, population rebound following overtrapping for furs, or other factors are contributing to beaver range expansion. We discuss rates and likely routes of tundra beaver colonization, as well as effects on permafrost, stream ice regimes, and freshwater and riparian habitat. Beaver ponds and associated hydrologic changes are thawing permafrost. Pond formation increases winter water temperatures in the pond and downstream, likely creating new and more varied aquatic habitat, but specific biological implications are unknown. Beavers create dynamic wetlands and are agents of disturbance that may enhance ecosystem responses to warming in the Arctic.}, language = {en} } @article{MurrayBraunReiners2018, author = {Murray, Kendra E. and Braun, Jean and Reiners, Peter W.}, title = {Toward Robust Interpretation of Low-Temperature Thermochronometers in Magmatic Terranes}, series = {Geochemistry, geophysics, geosystems}, volume = {19}, journal = {Geochemistry, geophysics, geosystems}, number = {10}, publisher = {American Geophysical Union}, address = {Washington}, issn = {1525-2027}, doi = {10.1029/2018GC007595}, pages = {3739 -- 3763}, year = {2018}, abstract = {Many regions central to our understanding of tectonics and landscape evolution are active or ancient magmatic terranes, and robust interpretation of low-temperature thermochronologic ages in these settings requires careful attention to the drivers of rock heating and cooling, including magmatism. However, we currently lack a quantitative framework for evaluating the potential role of magmatic coolingthat is, post-magmatic thermal relaxationin shaping cooling age patterns in regions with a history of intrusive magmatism. Here we use analytical approximations and numerical models to characterize how low-temperature thermochronometers document cooling inside and around plutons in steadily exhuming environments. Our models predict that the thermal field a pluton intrudes into, specifically the ambient temperatures relative to the closure temperature of a given thermochronometer, is as important as the pluton size and temperature in controlling the pattern and extent of thermochronometer resetting in the country rocks around a pluton. We identify one advective and several conductive timescales that govern the relationship between the crystallization and cooling ages inside a pluton. In synthetic vertical age-elevation relationships (AERs), resetting next to plutons results in changes in AER slope that could be misinterpreted as past changes in exhumation rate if the history of magmatism is not accounted for. Finally, we find that large midcrustal plutons, such as those emplaced at similar to 10-15-km depth, can reset the low-temperature thermochronometers far above them in the upper crusta result with considerable consequences for thermochronology in arcs and regions with a history of magmatic activity that may not have a surface expression.}, language = {en} } @article{WatheletGuillierRouxetal.2018, author = {Wathelet, Marc and Guillier, B. and Roux, P. and Cornou, C. and Ohrnberger, Matthias}, title = {Rayleigh wave three-component beamforming}, series = {Geophysical journal international}, volume = {215}, journal = {Geophysical journal international}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0956-540X}, doi = {10.1093/gji/ggy286}, pages = {507 -- 523}, year = {2018}, abstract = {The variation of Rayleigh ellipticity versus frequency is gaining popularity in site characterization. It becomes a necessary observable to complement dispersion curves when inverting shear wave velocity profiles. Various methods have been proposed so far to extract polarization from ambient vibrations recorded on a single three-component station or with an array of three-component sensors. If only absolute values were recovered 10 yr ago, new array-based techniques were recently proposed with enhanced efficiencies providing also the ellipticity sign. With array processing, higher-order modes are often detected even in the ellipticity domain. We suggest to explore the properties of a high-resolution beamforming where radial and vertical components are explicitly included. If N is the number of three-component sensors, 2N x 2N cross-spectral density matrices are calculated for all presumed directions of propagation. They are built with N radial and N vertical channels. As a first approach, steering vectors are designed to fit with Rayleigh wave properties: the phase shift between radial and vertical components is either -Pi/2 or Pi/2. We show that neglecting the ellipticity tilt due to attenuation has only minor effects on the results. Additionally, we prove analytically that it is possible to retrieve the ellipticity value from the usual maximization of the high-resolution beam power. The method is tested on synthetic data sets and on experimental data. Both are reference sites already analysed by several authors. A detailed comparison with previous results on these cases is provided.}, language = {en} } @article{AshastinaKuzminaRudayaetal.2018, author = {Ashastina, Kseniia and Kuzmina, Svetlana and Rudaya, Natalia and Troeva, Elena I. and Schoch, Werner H. and Roemermann, Christine and Reinecke, Jennifer and Otte, Volker and Savvinov, Grigoriy and Wesche, Karsten and Kienast, Frank}, title = {Woodlands and steppes}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {196}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2018.07.032}, pages = {38 -- 61}, year = {2018}, abstract = {Based on fossil organism remains including plant macrofossils, charcoal, pollen, and invertebrates preserved in syngenetic deposits of the Batagay permafrost sequence in the Siberian Yana Highlands, we reconstructed the environmental history during marine isotope stages (MIS) 6 to 2. Two fossil assemblages, exceptionally rich in plant remains, allowed for a detailed description of the palaeo-vegetation during two climate extremes of the Late Pleistocene, the onset of the last glacial maximum (LGM) and the last interglacial. In addition, altogether 41 assemblages were used to outline the vegetation history since the penultimate cold stage of MIS 6. Accordingly, meadow steppes analogue to modern communities of the phytosociological order Festucetalia lenensis formed the primary vegetation during the Saalian and Weichselian cold stages. Cold-resistant tundra-steppe communities (Carici rupestris-Kobresietea bellardii) as they occur above the treeline today were, in contrast to more northern locations, mostly lacking. During the last interglacial, open coniferous woodland similar to modern larch taiga was the primary vegetation at the site. Abundant charcoal indicates wildfire events during the last interglacial. Zoogenic disturbances of the local vegetation were indicated by the presence of ruderal plants, especially by abundant Urtica dioica, suggesting that the area was an interglacial refugium for large herbivores. Meadow steppes, which formed the primary vegetation during cold stages and provided potentially suitable pastures for herbivores, were a significant constituent of the plant cover in the Yana Highlands also under the full warm stage conditions of the last interglacial. Consequently, meadow steppes occurred in the Yana Highlands during the entire investigated timespan from MIS 6 to MIS 2 documenting a remarkable environmental stability. Thus, the proportion of meadow steppe vegetation merely shifted in response to the respectively prevailing climatic conditions. Their persistence indicates low precipitation and a relatively warm growing season throughout and beyond the late Pleistocene. The studied fossil record also proves that modern steppe occurrences in the Yana Highlands did not establish as late as in the Holocene but instead are relicts of a formerly continuous steppe belt extending from Central Siberia to Northeast Yakutia during the Pleistocene. The persistence of plants and invertebrates characteristic of meadow steppe vegetation in interior Yakutia throughout the late Quaternary indicates climatic continuity and documents the suitability of this region as a refugium also for other organisms of the Pleistocene mammoth steppe including the iconic large herbivores. (C)2018 Elsevier Ltd. All rights reserved.}, language = {en} } @article{MarkusMorozArnoldetal.2018, author = {Markus, Kathrin and Moroz, Lyuba and Arnold, Gabriele and Henckel, Daniela and Hiesinger, Harald and Rohrbach, Arno and Klemme, Stephan}, title = {Reflectance spectra of synthetic Fe-free ortho- and clinoenstatites in the UV/VIS/IR and implications for remote sensing detection of Fe-free pyroxenes on planetary surfaces}, series = {Planetary and space science}, volume = {159}, journal = {Planetary and space science}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2018.04.006}, pages = {43 -- 55}, year = {2018}, abstract = {Both enstatite spectra are very bright in the VIS and NIR and show almost neutral to slightly bluish spectral slopes with a steep absorption in the UV. Very low iron in the enstatites (below similar to 0.04 wt\% FeO) already results in weak albeit noticeable absorptions in the VNIR between 0.4 and 0.9 mu m. Orthoenstatite and clinoenstatite are not distinguishable based only on their spectra in the VIS and NIR. At the Reststrahlen bands in the MIR a systematic difference in the number and exact position of local minima at similar to 10 mu m between clinoenstatite and orthoenstatite is evident. This can be used to discern between the polymorphs in this wavelength range. Additionally, we can distinguish between Fe-free low- and high-Ca pyroxenes in the MIR.}, language = {en} } @article{WarkenFohlmeisterSchroederRitzrauhetal.2018, author = {Warken, Sophie Friederike and Fohlmeister, Jens Bernd and Schr{\"o}der-Ritzrauh, Andrea and Constantin, Silviu and Sp{\"o}tl, Christoph and Gerdes, Axel and Esper, Jan and Frank, Norbert and Arps, Jennifer and Terente, Mihai and Riechelmann, Dana Felicitas Christine and Mangini, Augusto and Scholz, Denis}, title = {Reconstruction of late Holocene autumn/winter precipitation variability in SW Romania from a high-resolution speleothem trace element record}, series = {Earth \& planetary science letters}, volume = {499}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2018.07.027}, pages = {122 -- 133}, year = {2018}, abstract = {We present the first high-resolution trace element (Mg/Ca, Sr/Ca, Ba/Ca) record from a stalagmite in southwestern Romania covering the last 3.6 ka, which provides the potential for quantitative climate reconstruction. Precise age control is based on three independent dating methods, in particular for the last 250 yr, where chemical lamina counting is combined with the identification of the 20th century radiocarbon bomb peak and Th-230/U dating. Long-term cave monitoring and model simulations of drip water and speleothem elemental variability indicate that precipitation-related processes are the main drivers of speleothem Mg/Ca ratios. Calibration against instrumental climate data shows a significant anti-correlation of speleothem Mg/Ca ratios with autumn/winter (October to March) precipitation (r = -0.61, p < 0.01), which is statistically robust when considering age uncertainties and auto-correlation. This relationship is used to develop a quantitative reconstruction of autumn/winter precipitation. During the late Holocene, our data suggest a heterogeneous pattern of past regional winter hydroclimate in the Carpathian/Balkan realm, along with intermittent weakening of the dominant influence of North Atlantic forcing. In agreement with other regional paleo-hydrological reconstructions, the observed variability reveals periodically occurring strong NW-SE hydro-climate gradients. We hypothesize, that this pattern is caused by shifts of the eastern edge of the area of influence of the NAO across central eastern Europe due to the confluence of North Atlantic forcing, and other climatic features such as the East Atlantic/Western Russia (EAWR) pattern. (C) 2018 Elsevier B.V. All rights reserved.}, language = {en} } @article{PaulyHelleMiramontetal.2018, author = {Pauly, Maren and Helle, Gerhard and Miramont, Cecile and Buentgen, Ulf and Treydte, Kerstin and Reinig, Frederick and Guibal, Frederic and Sivan, Olivier and Heinrich, Ingo and Riedel, Frank and Kromer, Bernd and Balanzategui, Daniel and Wacker, Lukas and Sookdeo, Adam and Brauer, Achim}, title = {Subfossil trees suggest enhanced Mediterranean hydroclimate variability at the onset of the Younger Dryas}, series = {Scientific reports}, volume = {8}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-018-32251-2}, pages = {8}, year = {2018}, abstract = {Nearly 13,000 years ago, the warming trend into the Holocene was sharply interrupted by a reversal to near glacial conditions. Climatic causes and ecological consequences of the Younger Dryas (YD) have been extensively studied, however proxy archives from the Mediterranean basin capturing this period are scarce and do not provide annual resolution. Here, we report a hydroclimatic reconstruction from stable isotopes (delta O-18, delta C-13) in subfossil pines from southern France. Growing before and during the transition period into the YD (12 900-12 600 cal BP), the trees provide an annually resolved, continuous sequence of atmospheric change. Isotopic signature of tree sourcewater (delta O-18(sw)) and estimates of relative air humidity were reconstructed as a proxy for variations in air mass origin and precipitation regime. We find a distinct increase in inter-annual variability of sourcewater isotopes (delta O-18(sw)), with three major downturn phases of increasing magnitude beginning at 12 740 cal BP. The observed variation most likely results from an amplified intensity of North Atlantic (low delta O-18(sw)) versus Mediterranean (high delta O-18(sw)) precipitation. This marked pattern of climate variability is not seen in records from higher latitudes and is likely a consequence of atmospheric circulation oscillations at the margin of the southward moving polar front.}, language = {en} } @article{QuandtTrumbullAltenbergeretal.2018, author = {Quandt, Dennis and Trumbull, Robert B. and Altenberger, Uwe and Cardona, Agustin and Romer, Rolf L. and Bayona, Germ{\´a}n A. and Ducea, Mihai N. and Valencia, Victor and Vasquez, Monica and Cortes, Elizabeth and Guzman, Georgina}, title = {The geochemistry and geochronology of Early Jurassic igneous rocks from the Sierra Nevada de Santa Marta, NW Colombia, and tectono-magmatic implications}, series = {Journal of South American earth sciences}, volume = {86}, journal = {Journal of South American earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {0895-9811}, doi = {10.1016/j.jsames.2018.06.019}, pages = {216 -- 230}, year = {2018}, abstract = {The Sierra Nevada de Santa Marta in NW Colombia is an isolated massif at the northernmost end of the Andes chain near the boundary with the Caribbean plate. Previous geologic mapping and K-Ar dating have shown that Jurassic plutonic and volcanic units make up a large part of the Santa Marta Massif (SMM). These rocks have been considered to be part of a Jurassic magmatic arc extending from NW Colombia to northern Chile, but without any geochemical basis for comparison. This paper reports on a geochemical and Sr-Nd-Pb isotope study of the Jurassic rocks in the SMM and provides 12 new U-Pb zircon ages from in-situ laser ICP-MS dating. The plutonic and volcanic units span a range from 45 to 78 wt.\% SiO2, with a dominance of intermediate to felsic compositions with SiO2 > 57 wt.\%. They classify as calc-alkaline, medium to high-K, metaluminous rocks with trace-element features typical for arc-derived magma series. In terms of their major and trace-element compositions, the SMM Jurassic units overlap with contemporary plutonic and volcanic rocks from other regions of the Central and Eastern Cordilleras of Colombia, and confirm an arc affinity. The new U-Pb ages range from 176 +/- 1 Ma to 192 +/- 2 Ma (n = 12), with most between 180 and 188 Ma (n = 7). The initial Sr isotope ratios (at 180 Ma) are between 0.7012 and 0.7071 (n = 29), with 3 outliers attributed to mobilization of Rb and/or Sr, Nearly all samples have negative( )epsilon Nd-(180) values between - 10.3 and 0.0 (n = 30), the two exceptions being only slightly positive (1.1 and 1.9). Measured Pb isotope ratios fall in a narrow range, with Pb-206/Pb-204 from 18.02 to 19.95, (207) Pb/(204) Pb from 15.56 to 15.67 and Pb-208/Pb-204 from 37.76 to 39.04 (n = 28). In the regional context of previous studies, these results confirm early Jurassic ages and an arc affinity for the widespread magmatism exposed in the eastern and northeastern Colombian Andes. We also note patterns in the distribution and composition of magmas. The magmatic activity in the Central Cordillera tends to be younger than in the Eastern Cordillera and is spatially more restricted to the vicinity of regional fault systems. In terms of composition, Jurassic igneous rocks in the Eastern Cordillera have systematically lower epsilon Nd-(180) values than those from the Central Cordillera, whereas the Pb isotope ratios overlap. We ascribe the Nd isotope variations to heterogeneity in the mantle source and/or degree of crustal contamination, whereas the Pb isotope ratios are crust-dominated and similar throughout the region. The spatio-temporal and compositional evolution of Jurassic magmatic rocks in the Northern Andes reflect the major plate kinematic readjustment between the Triassic and the Early Jurassic in the proto-Andean margin.}, language = {en} } @article{Iturrizaga2018, author = {Iturrizaga, Lasafam}, title = {Glacial landform assemblages and pedestal moraines in the Cordillera Check for Blanca (Peru)}, series = {Geomorphology : an international journal on pure and applied geomorphology}, volume = {318}, journal = {Geomorphology : an international journal on pure and applied geomorphology}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2018.06.012}, pages = {283 -- 302}, year = {2018}, abstract = {The article provides a contribution to the glacial geomorphology of tropical high-altitude mountains. It focuses on the diversity of glacial landforms in the Cordillera Blanca (Peru). The landforms are classified as individual landform types as well as in their hypsometric sequence. Their spatial arrangement is depicted in vertical series and summarised in a glacial-morphological altitudinal belt model. The glacial landforms are analysed in a genetic succession from the moraine-delimited glacier forefields to the excessive pedestal moraines and taking account of the topographical conditions in the verticality. The Pleistocene glacial relief formation is considered as one of the dominating factors in the development of the moraine types. The sediments are on the one hand in situ deposition forms and on the other depositions dislocated by mass movements and represent paraglacial landforms. Using the example of the Paron Valley in the Artesonraju-Huandoy Massif and neighbouring valleys, the article provides a typology of the range of glacial and paraglacial landforms based on a holistic glacial landsystem approach with special reference to pedestal moraines. (C) 2018 Elsevier B.V. All rights reserved.}, language = {en} } @article{Hudson2018, author = {Hudson, Paul}, title = {A comparison of definitions of affordability for flood risk adaption measures}, series = {Mitigation and adaptation strategies for global change : an international journal devoted to scientific, engineering, socio-economic and policy responses to environmental change}, volume = {23}, journal = {Mitigation and adaptation strategies for global change : an international journal devoted to scientific, engineering, socio-economic and policy responses to environmental change}, number = {7}, publisher = {Springer}, address = {Dordrecht}, issn = {1381-2386}, doi = {10.1007/s11027-017-9769-5}, pages = {1019 -- 1038}, year = {2018}, abstract = {Risk-based insurance is a commonly proposed and discussed flood risk adaptation mechanism in policy debates across the world such as in the United Kingdom and the United States of America. However, both risk-based premiums and growing risk pose increasing difficulties for insurance to remain affordable. An empirical concept of affordability is required as the affordability of adaption strategies is an important concern for policymakers, yet such a concept is not often examined. Therefore, a robust metric with a commonly acceptable affordability threshold is required. A robust metric allows for a previously normative concept to be quantified in monetary terms, and in this way, the metric is rendered more suitable for integration into public policy debates. This paper investigates the degree to which risk-based flood insurance premiums are unaffordable in Europe. In addition, this paper compares the outcomes generated by three different definitions of unaffordability in order to investigate the most robust definition. In doing so, the residual income definition was found to be the least sensitive to changes in the threshold. While this paper focuses on Europe, the selected definition can be employed elsewhere in the world and across adaption measures in order to develop a common metric for indicating the potential unaffordability problem.}, language = {en} } @article{AwaisAhmadKhanetal.2018, author = {Awais, Muhammad and Ahmad, Rafiq and Khan, Nadeem and Garapati, Prashanth and Shahzad, Muhammad and Afroz, Amber and Rashid, Umer and Khan, Sabaz Ali}, title = {Transformation of tomato variety rio grande with drought resistant transcription factor gene ATAF1 and its molecular analysis}, series = {Pakistan Journal of Botany}, volume = {50}, journal = {Pakistan Journal of Botany}, number = {5}, publisher = {Pakistan botanic soc}, address = {Karachi}, issn = {0556-3321}, pages = {1811 -- 1820}, year = {2018}, abstract = {Tomato (Solanum lycopersicum L.) being an important vegetable is cultivated and used throughout the world. It not only contributes in fulfilling the basic nutritional requirements of the human body but also has many health benefits due to its rich biochemical composition. However, its production at large scale is hampered by many limiting factors such as biotic and abiotic stresses. Among the different abiotic stresses, drought poses drastic impact on tomato yield. Drought stress is genetically regulated by many transcription factors that not only regulate the stress responsive mechanism but also facilitate the growth and development of tomato plants. NAC is an important stress related transcription factor genes family, and the ATAF1 gene, a member of this family, is involved in ABA signaling and stress response. In this study, tomato variety Rio Drande was transformed with drought resistant ATAF1 gene via Agrobacterium mediated gene transformation method. The ATAF1 gene was first cloned in the pK7WFG2 vector having kanamycin selectable marker and then it was introduced in the Agrobacterium tumefaciens strain GV3101 through heat shock method. The tomato cotyledon and hypocotyl ex-plants of variety "Rio Ggrande" were cultured on callus induction medium (MS + 2.5 mg/L IAA + 2 mg/L BAP). The calli were then infected with Agrobacterium tumefaciens strain GV3101 containing ATAF1 gene and selection was carried out on the kanamycin selectable medium (MS + 100 mg/L Kan), and were regenerated on MS medium with 1 mg/L IAA + 1 mg/L BAP. Out of 216 putative transformed calli, 13 calli were able to regenerate on the selection medium. Of the 13 calli, three transgenic tomato plantlets were recovered, and these were confirmed through PCR analysis for the presence of 432 bp fragment of ATAF1 gene. The transformation protocol reported here can be used to generate drought resistant tomato plants in future.}, language = {en} } @article{TolorzaMohrCarretieretal.2019, author = {Tolorza, Violeta and Mohr, Christian Heinrich and Carretier, Sebastien and Serey, Amador and Sepulveda, Sergio A. and Tapia, Joseline and Pinto, Luisa}, title = {Suspended sediments in chilean rivers reveal low postseismic erosion after the maule earthquake (Mw 8.8) during a severe drought}, series = {Journal of geophysical research : Earth surface}, volume = {124}, journal = {Journal of geophysical research : Earth surface}, number = {6}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9003}, doi = {10.1029/2018JF004766}, pages = {1378 -- 1397}, year = {2019}, abstract = {We address the question of whether all large-magnitude earthquakes produce an erosion peak in the subaerial components of fluvial catchments. We evaluate the sediment flux response to the Maule earthquake in the Chilean Andes (Mw 8.8) using daily suspended sediment records from 31 river gauges. The catchments cover drainage areas of 350 to around 10,000 km(2), including a wide range of topographic slopes and vegetation cover of the Andean western flank. We compare the 3- to 8-year postseismic record of sediment flux to each of the following preseismic periods: (1) all preseismic data, (2) a 3-year period prior to the seismic event, and (3) the driest preseismic periods, as drought conditions prevailed in the postseismic period. Following the earthquake, no increases in suspended sediment flux were observed for moderate to high percentiles of the streamflow distribution (mean, median, and >= 75th percentile). However, more than half of the examined stations showed increased sediment flux during baseflow. By using a Random Forest approach, we evaluate the contributions of seismic intensities, peak ground accelerations, co-seismic landslides, hydroclimatic conditions, topography, lithology, and land cover to explain the observed changes in suspended sediment concentration and fluxes. We find that the best predictors are hillslope gradient, low-vegetation cover, and changes in streamflow discharge. This finding suggests a combined first-order control of topography, land cover, and hydrology on the catchment-wide erosion response. We infer a reduced sediment connectivity due to the postseismic drought, which increased the residence time of sediment detached and remobilized following the Maule earthquake.}, language = {en} } @article{FortesaGarciaComendadorCalsamigliaetal.2019, author = {Fortesa, Josep and Garc{\´i}a-Comendador, Julian and Calsamiglia, A. and L{\´o}pez-Taraz{\´o}n, Jos{\´e} Andr{\´e}s and Latron, J. and Alorda, B. and Estrany, Joan}, title = {Comparison of stage/discharge rating curves derived from different recording systems}, series = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, volume = {665}, journal = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, publisher = {Elsevier Science}, address = {Amsterdam}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2019.02.158}, pages = {968 -- 981}, year = {2019}, abstract = {Obtaining representative hydrometric values is essential for characterizing extreme events, hydrological dynamics and detecting possible changes on the long-term hydrology. Reliability of streamflow data requires a temporal continuity and a maintenance of the gauging stations, which data are affected by epistemic and random sources of error. An assessment of discharge meterings' and stage-discharge rating curves' uncertainties were carried out by comparing the accuracy of the measuring instruments of two different hydrometric networks (i.e., one analogical and one digital) established in the same river location at the Mediterranean island of Mallorca. Furthermore, the effects of such uncertainties were assessed on the hydrological dynamics, considering the significant global change impacts beset this island. Evaluation was developed at four representative gauging stations of the hydrographic network with analogic (≈40 years) and digital (≈10 years) data series. The study revealed that the largest source of uncertainty in the analogical (28 to 274\%) and in the digital (17-37\%) networks were the stage-discharge rating curves. Their impact on the water resources was also evaluated at the event and annual scales, resulting in an average difference of water yields of 183\% and 142\% respectively. Such improvement on the comprehension of hydrometric networks uncertainties will dramatically benefit the interpretation of the long-term streamflow by providing better insights into the hydrologic and flood hazard planning, management and modelling.}, language = {en} } @article{MorandiKailToedteretal.2017, author = {Morandi, Bertrand and Kail, Jochem and T{\"o}dter, Anne and Wolter, Christian and Piegay, Herve}, title = {Diverse Approaches to Implement and Monitor River Restoration}, series = {Environmental Management}, volume = {60}, journal = {Environmental Management}, publisher = {Springer}, address = {New York}, issn = {0364-152X}, doi = {10.1007/s00267-017-0923-3}, pages = {931 -- 946}, year = {2017}, abstract = {River restoration is a main emphasis of river management in European countries. Cross-national comparisons of its implementation are still rare in scientific literature. Based on French and German national censuses, this study compares river restoration practices and monitoring by analysing 102 French and 270 German projects. This comparison aims to draw a spatial and temporal framework of restoration practices in both countries to identify potential drivers of cross-national similarities and differences. The results underline four major trends: (1) a lag of almost 15 years in river restoration implementation between France and Germany, with a consequently higher share of projects in Germany than in France, (2) substantial similarities in restored reach characteristics, short reach length, small rivers, and in "agricultural" areas, (3) good correspondences between stressors identified and restoration measures implemented. Morphological alterations were the most important highlighted stressors. River morphology enhancement, especially instream enhancements, were the most frequently implemented restoration measures. Some differences exist in specific restoration practices, as river continuity restoration were most frequently implemented in French projects, while large wood introduction or channel re-braiding were most frequently implemented in German projects, and (4) some quantitative and qualitative differences in monitoring practices and a significant lack of project monitoring, especially in Germany compared to France. These similarities and differences between Germany and France in restoration application and monitoring possibly result from a complex set of drivers that might be difficult to untangle (e.g., environmental, technical, political, cultural).}, language = {en} } @article{HuckWohlwendCoimbraetal.2017, author = {Huck, Stefan and Wohlwend, Stephan and Coimbra, Rute and Christ, Nicolas and Weissert, Helmut}, title = {Disentangling shallow-water bulk carbonate carbon isotope archives with evidence for multi-stage diagenesis}, series = {The depositional record}, volume = {3}, journal = {The depositional record}, publisher = {Wiley}, address = {Hoboken}, issn = {2055-4877}, doi = {10.1002/dep2.35}, pages = {233 -- 257}, year = {2017}, abstract = {Disentangling shallow-water bulk carbonate carbon isotope archives into primary and diagenetic components is a notoriously difficult task and even diagenetically screened records often provide chemostratigraphic patterns that significantly differ from global signals. This is mainly caused by the polygenetic nature of shallow-water carbonate substrates, local carbon cycle processes causing considerable neritic-pelagic isotope gradients and the presence of hiatal surfaces resulting in extremely low carbonate preservation rates. Provided here is an in-depth petrographic and geochemical evaluation of different carbonate phases of a mid-Cretaceous (Barremian-Aptian) shallow-water limestone succession (Jabal Madar section) deposited on the tropical Arabian carbonate platform in Oman. The superposition of stable isotope signatures of identified carbonate phases causes a complex and often noisy bulk carbon isotope pattern. Blocky sparite cements filling intergranular pores and bioclastic voids evidence intermediate to (arguably) deep burial diagenetic conditions during their formation, owing to different timing or differential faulting promoting the circulation of fluids from variable sources. In contrast, sparite cements filling sub-vertical veins reveal a rock-buffered diagenetic fluid composition with an intriguing moderate enrichment in 13C, probably due to fractionation during pressure release in the context of the Miocene exhumation of the carbonate platform under study. The presence of abundant, replacive dedolomite in mud-supported limestone samples forced negative carbon and oxygen isotope changes that are either associated with the thermal breakdown of organic matter in the deep burial realm or the expulsion of buried meteoric water in the intermediate burial realm. Notwithstanding the documented stratigraphically variable and often facies-related impact of different diagenetic fluids on the bulk-rock stable isotope signature, the identification of diagenetic end-members defined δ13C and δ18O threshold values that allowed the most reliable 'primary' bulk carbon isotope signatures to be extracted. Most importantly, this approach exemplifies how to place regional shallow-water stable isotope patterns with evidence for a complex multi-stage diagenetic history into a supraregional or even global context.}, language = {en} } @article{KruseGerdesKathetal.2018, author = {Kruse, Stefan and Gerdes, Alexander and Kath, Nadja J. and Herzschuh, Ulrike}, title = {Implementing spatially explicit wind-driven seed and pollen dispersal in the individual-based larch simulation model}, series = {Geoscientific model development : an interactive open access journal of the European Geosciences Union}, volume = {11}, journal = {Geoscientific model development : an interactive open access journal of the European Geosciences Union}, number = {11}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1991-959X}, doi = {10.5194/gmd-11-4451-2018}, pages = {4451 -- 4467}, year = {2018}, abstract = {It is of major interest to estimate the feedback of arctic ecosystems to the global warming we expect in upcoming decades. The speed of this response is driven by the potential of species to migrate, tracking their climate optimum. For this, sessile plants have to produce and disperse seeds to newly available habitats, and pollination of ovules is needed for the seeds to be viable. These two processes are also the vectors that pass genetic information through a population. A restricted exchange among subpopulations might lead to a maladapted population due to diversity losses. Hence, a realistic implementation of these dispersal processes into a simulation model would allow an assessment of the importance of diversity for the migration of plant species in various environments worldwide. To date, dynamic global vegetation models have been optimized for a global application and overestimate the migration of biome shifts in currently warming temperatures. We hypothesize that this is caused by neglecting important fine-scale processes, which are necessary to estimate realistic vegetation trajectories. Recently, we built and parameterized a simulation model LAVESI for larches that dominate the latitudinal treelines in the northernmost areas of Siberia. In this study, we updated the vegetation model by including seed and pollen dispersal driven by wind speed and direction. The seed dispersal is modelled as a ballistic flight, and for the pollination of ovules of seeds produced, we implemented a wind-determined and distance-dependent probability distribution function using a von Mises distribution to select the pollen donor. A local sensitivity analysis of both processes supported the robustness of the model's results to the parameterization, although it highlighted the importance of recruitment and seed dispersal traits for migration rates. This individual-based and spatially explicit implementation of both dispersal processes makes it easily feasible to inherit plant traits and genetic information to assess the impact of migration processes on the genetics. Finally, we suggest how the final model can be applied to substantially help in unveiling the important drivers of migration dynamics and, with this, guide the improvement of recent global vegetation models.}, language = {en} } @article{SoaresYamazakiMatzkaetal.2018, author = {Soares, Gabriel and Yamazaki, Yosuke and Matzka, J{\"u}rgen and Pinheiro, Katia and Morschhauser, Achim and Stolle, Claudia and Alken, Patrick}, title = {Equatorial counter electrojet longitudinal and seasonal variablity in the American sector}, series = {Journal of geophysical research : Space physics}, volume = {123}, journal = {Journal of geophysical research : Space physics}, number = {11}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1029/2018JA025968}, pages = {9906 -- 9920}, year = {2018}, abstract = {The equatorial electrojet occasionally reverses during morning and afternoon hours, leading to periods of westward current in the ionospheric E region that are known as counter electrojet (CEJ) events. We present the first analysis of CEJ climatology and CEJ dependence on solar flux and lunar phase for the Brazilian sector, based on an extensive ground-based data set for the years 2008 to 2017 from the geomagnetic observatory Tatuoca (1.2 degrees S, 48.5 degrees W), and we compare it to the results found for Huancayo (12.0 degrees S, 75.3 degrees W) observatory in the Peruvian sector. We found a predominance of morning CEJ events for both sectors. The afternoon CEJ occurrence rate in the Brazilian sector is twice as high as in the Peruvian sector. The afternoon CEJ occurrence rate strongly depends on season, with maximum rates occurring during the northern-hemisphere summer for the Brazilian sector and during the northern-hemisphere winter for the Peruvian sector. Significant discrepancies between the two sectors are also found for morning CEJ rates during the northern-hemisphere summer. These longitudinal differences are in agreement with a CEJ climatology derived from contemporary Swarm satellite data and can be attributed in part to the well-known longitudinal wave-4 structure in the background equatorial electrojet strength that results from nonmigrating solar tides and stationary planetary waves. Simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model show that the remaining longitudinal variability in CEJ during northern summer can be explained by the effect of migrating tides in the presence of the varying geomagnetic field in the South Atlantic Anomaly.}, language = {en} } @article{AsgarimehrWickertReich2018, author = {Asgarimehr, Milad and Wickert, Jens and Reich, Sebastian}, title = {TDS-1 GNSS Reflectometry}, series = {IEEE journal of selected topics in applied earth observations and remote sensing}, volume = {11}, journal = {IEEE journal of selected topics in applied earth observations and remote sensing}, number = {11}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {1939-1404}, doi = {10.1109/JSTARS.2018.2873241}, pages = {4534 -- 4541}, year = {2018}, abstract = {This study presents the development and a systematic evaluation study of GNSS reflectometry wind speeds. After establishing a wind speed retrieval algorithm, UK TechDemoSat-1 (TDS-1) derived winds, from May 2015 to July 2017, are compared to the Advanced Scatterometer (ASCAT). ERA-Interim wind fields of the European Centre for Medium-range Weather Forecasts (ECMWF) and in situ observation from Tropical Atmosphere Ocean buoy array in the Pacific are taken as reference. One-year averaged TDS-1 global winds demonstrate small differences with ECMWF in a majority of areas as well as discuss under- and overestimations. The pioneering TDS-1 winds demonstrate a root-mean-squared error (RMSE) and bias of 2.77 and -0.33 m/s, which are comparable to the RMSE and bias derived by ASCAT winds, as large as 2.31 and 0.25 m/s, respectively. Using buoys measurements as reference, RMSE and bias of 2.23 and -0.03 m/s for TDS-1 as well as 1.40 and -0.68 m/s for ASCAT are obtained. Utilizing rain microwave-infrared estimates of the Tropical Rainfall Measuring Mission, rain-affected observation of both ASCAT and TDS-1 are collected and evaluated. Although ASCAT winds show a significant performance degradation resulting in an RMSE and bias of 3.16 and 1.03 m/s, respectively, during rain condition, TDS-1 shows a more reliable performance with an RMSE and bias of 2.94 and -0.21 m/s, respectively, which indicates the promising capability of GNSS forward scattering for wind retrievals during rain. A decrease in TDS-1-derived bistatic radar cross sections during rain events, at weak winds, is also demonstrated.}, language = {en} } @article{TotzPetriLehmannetal.2018, author = {Totz, Sonja Juliana and Petri, Stefan and Lehmann, Jascha and Coumou, Dim}, title = {Regional Changes in the Mean Position and Variability of the Tropical Edge}, series = {Geophysical research letters}, volume = {45}, journal = {Geophysical research letters}, number = {21}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2018GL079911}, pages = {12076 -- 12084}, year = {2018}, abstract = {Recent studies indicate that the tropical belt has been expanding during recent decades, which can significantly influence precipitation in subtropical climates. Often the location of the tropical border is identified using the Hadley cell edge (HCE) or the subtropical jet stream (STJ), but most studies concentrated on the zonal-mean state, thereby missing regional impacts. Here we detect longitudinal-resolved trends in STJ cores and HCEs over 1979-2016 in both hemispheres at a higher spatial and temporal resolution than previous studies. Besides pronounced regional trend differences in both sign and magnitude, we show that winter HCE and STJ variability increased in the Mediterranean region and decreased over the American and Asian continents. Rainfall variability in these regions changed likewise, and most of those changes can be explained by changes in HCE/STJ variability. This highlights the importance of understanding future tropical belt changes both regionally and in terms of variability. Plain Language Summary We applied a new network-based method to detect motion of the tropical climate border with longitudinal resolution. Depending on the longitudinal position, there are differences in both direction and magnitude of the border motion. In addition, we demonstrate that the rainfall variability is increasing in the Mediterranean region and decreasing over the American and Asian continents, which can be explained by the variability of the tropical belt location.}, language = {en} } @article{YalewPilzSchweitzeretal.2018, author = {Yalew, S. G. and Pilz, Tobias and Schweitzer, C. and Liersch, Stefan and van der Kwast, J. and van Griensven, A. and Mul, Marloes L. and Dickens, Chris and van der Zaag, Pieter}, title = {Coupling land-use change and hydrologic models for quantification of catchment ecosystem services}, series = {Environmental modelling \& software with environment data news}, volume = {109}, journal = {Environmental modelling \& software with environment data news}, publisher = {Elsevier}, address = {Oxford}, issn = {1364-8152}, doi = {10.1016/j.envsoft.2018.08.029}, pages = {315 -- 328}, year = {2018}, abstract = {Representation of land-use and hydrologic interactions in respective models has traditionally been problematic. The use of static land-use in most hydrologic models or that of the use of simple hydrologic proxies in land-use change models call for more integrated approaches. The objective of this study is to assess whether dynamic feedback between land-use change and hydrology can (1) improve model performances, and/or (2) produce a more realistic quantification of ecosystem services. To test this, we coupled a land-use change model and a hydrologic mode. First, the land-use change and the hydrologic models were separately developed and calibrated. Then, the two models were dynamically coupled to exchange data at yearly time-steps. The approach is applied to a catchment in South Africa. Performance of coupled models when compared to the uncoupled models were marginal, but the coupled models excelled at the quantification of catchment ecosystem services more robustly.}, language = {en} } @misc{HeidbachRajabiCuietal.2018, author = {Heidbach, Oliver and Rajabi, Mojtaba and Cui, Xiaofeng and Fuchs, Karl and Mueller, Birgit and Reinecker, John and Reiter, Karsten and Tingay, Mark and Wenzel, Friedemann and Xie, Furen and Ziegler, Moritz O. and Zoback, Mary-Lou and Zoback, Mark}, title = {The World Stress Map database release 2016}, series = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, volume = {744}, journal = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-1951}, doi = {10.1016/j.tecto.2018.07.007}, pages = {484 -- 498}, year = {2018}, abstract = {Knowledge of the present-day crustal in-situ stress field is a key for the understanding of geodynamic processes such as global plate tectonics and earthquakes. It is also essential for the management of geo-reservoirs and underground storage sites for energy and waste. Since 1986, the World Stress Map (WSM) project has systematically compiled the orientation of maximum horizontal stress (S-Hmax). For the 30th anniversary of the project, the WSM database has been updated significantly with 42,870 data records which is double the amount of data in comparison to the database release in 2008. The update focuses on areas with previously sparse data coverage to resolve the stress pattern on different spatial scales. In this paper, we present details of the new WSM database release 2016 and an analysis of global and regional stress pattern. With the higher data density, we can now resolve stress pattern heterogeneities from plate-wide to local scales. In particular, we show two examples of 40 degrees-60 degrees S-Hmax rotations within 70 km. These rotations can be used as proxies to better understand the relative importance of plate boundary forces that control the long wave-length pattern in comparison to regional and local controls of the crustal stress state. In the new WSM project phase IV that started in 2017, we will continue to further refine the information on the S-Hmax orientation and the stress regime. However, we will also focus on the compilation of stress magnitude data as this information is essential for the calibration of geomechanical-numerical models. This enables us to derive a 3-D continuous description of the stress tensor from point-wise and incomplete stress tensor information provided with the WSM database. Such forward models are required for safety aspects of anthropogenic activities in the underground and for a better understanding of tectonic processes such as the earthquake cycle.}, language = {en} } @article{FuchsFoersterBrauneetal.2018, author = {Fuchs, Sven and F{\"o}rster, Hans-J{\"u}rgen and Braune, K. and F{\"o}rster, A.}, title = {Calculation of Thermal Conductivity of Low-Porous, Isotropic Plutonic Rocks of the Crust at Ambient Conditions From Modal Mineralogy and Porosity}, series = {Journal of geophysical research : Solid earth}, volume = {123}, journal = {Journal of geophysical research : Solid earth}, number = {10}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9313}, doi = {10.1029/2018JB016287}, pages = {8602 -- 8614}, year = {2018}, abstract = {Thermal conductivity (lambda) is an essential physical property of minerals and rocks and fundamental in constraining the thermal field of the lithosphere. In case that adequate samples to measure lambda are not available, it could be indirectly inferred from calculation. One of the most widely applied indirect methods for rocks involve modal mineralogy and porosity as parameters that are incorporated into mathematical mean or mixing models. Robust inferences from these approaches for crystalline rocks were impeded by a small number of studied samples or restriction to certain rock types. We employ this method and examine its applicability to low-porosity plutonic rocks by calculating bulk thermal conductivity lambda(b) for 45 samples covering the entire range from gabbro/diorite to granite. We show that the use of the harmonic-mean model for both rock matrix and porosity provided a good match between lambda(b.meas) and lambda(b.calc) of <10\% deviation (2 sigma), with relative and absolute errors amounting to 1.49.7\% and 4.44.9\%, respectively. The results of our study constitute a big step forward to a robust conclusion on the overall applicability of the harmonic-mean model for inferring lambda(b) of isotropic, low-porosity, mafic to silicic plutonic and metamorphic rocks with an acceptable magnitude of error. Drill cuttings and enclaves form particularly interesting objects for application of this method, as they are poorly suited for direct measurement. Well-derived lambda values for those rocks would permit to calculate heat flow and to model more profoundly the thermal state of the deeper lithosphere.}, language = {en} } @article{Ayzel2018, author = {Ayzel, Georgy V.}, title = {Runoff predictions in ungauged arctic basins using conceptual models forced by reanalysis data}, series = {Water Resources}, volume = {45}, journal = {Water Resources}, publisher = {Pleiades Publ.}, address = {New York}, issn = {0097-8078}, doi = {10.1134/S0097807818060180}, pages = {S1 -- S7}, year = {2018}, abstract = {Due to global warming, the problem of assessing water resources and their vulnerability to climate drivers in the Arctic region has become a focus in the recent years. This study is aimed at investigating three lumped hydrological models to predict daily runoff of large-scale Arctic basins in the case of substantial data scarcity. All models were driven only by meteorological forcing reanalysis dataset without any additional information about landscape, soil, or vegetation cover properties of the studied basins. Model parameter regionalization based on transferring the whole parameter set showed good efficiency for predictions in ungauged basins. We run a blind test of the proposed methodology for ensemble runoff predictions on five sub-basins, for which only monthly observations were available, and obtained promising results for current water resources assessment for a broad domain of ungauged basins in the Russian Arctic.}, language = {en} } @article{WickertSchildgen2019, author = {Wickert, Andrew D. and Schildgen, Taylor F.}, title = {Long-profile evolution of transport-limited gravel-bed rivers}, series = {Earth surface dynamics}, volume = {7}, journal = {Earth surface dynamics}, number = {1}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {2196-6311}, doi = {10.5194/esurf-7-17-2019}, pages = {17 -- 43}, year = {2019}, abstract = {Alluvial and transport-limited bedrock rivers constitute the majority of fluvial systems on Earth. Their long profiles hold clues to their present state and past evolution. We currently possess first-principles-based governing equations for flow, sediment transport, and channel morphodynamics in these systems, which we lack for detachment-limited bedrock rivers. Here we formally couple these equations for transport-limited gravel-bed river long-profile evolution. The result is a new predictive relationship whose functional form and parameters are grounded in theory and defined through experimental data. From this, we produce a power-law analytical solution and a finite-difference numerical solution to long-profile evolution. Steady-state channel concavity and steepness are diagnostic of external drivers: concavity decreases with increasing uplift rate, and steepness increases with an increasing sediment-to-water supply ratio. Constraining free parameters explains common observations of river form: to match observed channel concavities, gravel-sized sediments must weather and fine - typically rapidly - and valleys typically should widen gradually. To match the empirical square-root width-discharge scaling in equilibrium-width gravel-bed rivers, downstream fining must occur. The ability to assign a cause to such observations is the direct result of a deductive approach to developing equations for landscape evolution.}, language = {en} } @article{SchuetzWinterleitnerHuenges2018, author = {Sch{\"u}tz, Felina and Winterleitner, Gerd and Huenges, Ernst}, title = {Geothermal exploration in a sedimentary basin}, series = {Geothermal Energy}, volume = {6}, journal = {Geothermal Energy}, number = {1}, publisher = {Springer}, address = {London}, issn = {2195-9706}, doi = {10.1186/s40517-018-0091-6}, pages = {23}, year = {2018}, abstract = {The lateral and vertical temperature distribution in Oman is so far only poorly understood, particularly in the area between Muscat and the Batinah coast, which is the area of this study and which is composed of Cenozoic sediments developed as part of a foreland basin of the Makran Thrust Zone. Temperature logs (T-logs) were run and physical rock properties of the sediments were analyzed to understand the temperature distribution, thermal and hydraulic properties, and heat-transport processes within the sedimentary cover of northern Oman. An advective component is evident in the otherwise conduction-dominated geothermal play system, and is caused by both topography and density driven flow. Calculated temperature gradients (T-gradients) in two wells that represent conductive conditions are 18.7 and 19.5 °C km-1, corresponding to about 70-90 °C at 2000-3000 m depth. This indicates a geothermal potential that can be used for energy intensive applications like cooling or water desalinization. Sedimentation in the foreland basin was initiated after the obduction of the Semail Ophiolite in the late Campanian, and reflects the complex history of alternating periods of transgressive and regressive sequences with erosion of the Oman Mountains. Thermal and hydraulic parameters were analyzed of the basin's heterogeneous clastic and carbonate sedimentary sequence. Surface heat-flow values of 46.4 and 47.9 mW m-2 were calculated from the T-logs and calculated thermal conductivity values in two wells. The results of this study serve as a starting point for assessing different geothermal applications that may be suitable for northern Oman.}, language = {en} } @article{UberVandervaereZinetal.2018, author = {Uber, Magdalena and Vandervaere, Jean-Pierre and Zin, Isabella and Braud, Isabelle and Heistermann, Maik and Legout, Cedric and Molinie, Gilles and Nord, Guillaume}, title = {How does initial soil moisture influence the hydrological response? A case study from southern France}, series = {Hydrology and earth system sciences : HESS}, volume = {22}, journal = {Hydrology and earth system sciences : HESS}, number = {12}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1027-5606}, doi = {10.5194/hess-22-6127-2018}, pages = {6127 -- 6146}, year = {2018}, abstract = {The phi(ev) is calculated from high-resolution discharge and precipitation data for several rain events with a cumulative precipitation P-cum ranging from less than 5mm to more than 80 mm. Because of the high uncertainty of phi(ev) associated with the hydrograph separation method, phi(ev) is calculated with several methods, including graphical methods, digital filters and a tracer-based method. The results indicate that the hydrological response depends on (theta) over bar (ini): during dry conditions phi(ev) is consistently below 0.1, even for events with high and intense precipitation. Above a threshold of (theta) over bar (ini) = 34 vol \% phi(ev) can reach values up to 0.99 but there is a high scatter. Some variability can be explained with a weak correlation of phi(ev) with P-cum and rain intensity, but a considerable part of the variability remains unexplained. It is concluded that threshold-based methods can be helpful to prevent overestimation of the hydrological response during dry catchment conditions. The impact of soil moisture on the hydrological response during wet catchment conditions, however, is still insufficiently understood and cannot be generalized based on the present results.}, language = {en} } @article{HimiCasadoSendrosetal.2018, author = {Himi, Mahjoub and Casado, Ismael and Sendros, Alex and Lovera, Raul and Rivero, Lluis and Casas, Albert}, title = {Assessing preferential seepage and monitoring mortar injection through an earthen dam settled over a gypsiferous substrate using combined geophysical methods}, series = {Engineering geology}, volume = {246}, journal = {Engineering geology}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0013-7952}, doi = {10.1016/j.enggeo.2018.10.002}, pages = {212 -- 221}, year = {2018}, abstract = {For several decades the Sant Llorenc de Montgai reservoir has experienced different problems that could affect the safety of the engineering structure. For this reason, several corrective actions have been taken over the years. Here, we present a study involving complementary geophysical methods including electrical resistivity tomography, seismic refraction tomography and frequency-domain electromagnetic surveys. The analysis of the inverted electrical resistivity tomography cross-sections combined with the seismic refraction results and land subsidence monitoring data show the likely mechanism of abnormal seepage. The areas where mortar injections were applied as a corrective measure are also clearly delineated. In addition, the evolution of the state of the embankment has been established from two successive electrical resistivity tomography surveys in the last two decades. The results show areas where corrective mortar injections have been effective, while in other areas new abnormal seepage has been detected. The lithological heterogeneity of the bedrock, especially the dissolution of gypsum-rich rocks, induced subsidence effects and caused abnormal seepage in different areas along the embankment. Our results indicate how corrective solutions can be optimized to reduce the cost of corrective engineering interventions.}, language = {en} } @article{AsgarimehrZavorotnyWickertetal.2018, author = {Asgarimehr, Milad and Zavorotny, Valery and Wickert, Jens and Reich, Sebastian}, title = {Can GNSS Reflectometry Detect Precipitation Over Oceans?}, series = {Geophysical research letters}, volume = {45}, journal = {Geophysical research letters}, number = {22}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2018GL079708}, pages = {12585 -- 12592}, year = {2018}, abstract = {For the first time, a rain signature in Global Navigation Satellite System Reflectometry (GNSS-R) observations is demonstrated. Based on the argument that the forward quasi-specular scattering relies upon surface gravity waves with lengths larger than several wavelengths of the reflected signal, a commonly made conclusion is that the scatterometric GNSS-R measurements are not sensitive to the surface small-scale roughness generated by raindrops impinging on the ocean surface. On the contrary, this study presents an evidence that the bistatic radar cross section sigma(0) derived from TechDemoSat-1 data is reduced due to rain at weak winds, lower than approximate to 6 m/s. The decrease is as large as approximate to 0.7 dB at the wind speed of 3 m/s due to a precipitation of 0-2 mm/hr. The simulations based on the recently published scattering theory provide a plausible explanation for this phenomenon which potentially enables the GNSS-R technique to detect precipitation over oceans at low winds.}, language = {en} } @article{MilewskiChabrillatBehling2017, author = {Milewski, Robert and Chabrillat, Sabine and Behling, Robert}, title = {Analyses of Recent Sediment Surface Dynamic of a Namibian Kalahari Salt Pan Based on Multitemporal Landsat and Hyperspectral Hyperion Data}, series = {Remote Sensing}, volume = {9}, journal = {Remote Sensing}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {2072-4292}, doi = {10.3390/rs9020170}, pages = {24}, year = {2017}, abstract = {This study combines spaceborne multitemporal and hyperspectral data to analyze the spatial distribution of surface evaporite minerals and changes in a semi-arid depositional environment associated with episodic flooding events, the Omongwa salt pan (Kalahari, Namibia). The dynamic of the surface crust is evaluated by a change-detection approach using the Iterative-reweighted Multivariate Alteration Detection (IR-MAD) based on the Landsat archive imagery from 1984 to 2015. The results show that the salt pan is a highly dynamic and heterogeneous landform. A change gradient is observed from very stable pan border to a highly dynamic central pan. On the basis of hyperspectral EO-1 Hyperion images, the current distribution of surface evaporite minerals is characterized using Spectral Mixture Analysis (SMA). Assessment of field and image endmembers revealed that the pan surface can be categorized into three major crust types based on diagnostic absorption features and mineralogical ground truth data. The mineralogical crust types are related to different zones of surface change as well as pan morphology that influences brine flow during the pan inundation and desiccation cycles. These combined information are used to spatially map depositional environments where the more dynamic halite crust concentrates in lower areas although stable gypsum and calcite/sepiolite crusts appear in higher elevated areas.}, language = {en} } @article{FoersterRhede2006, author = {F{\"o}rster, Hans-J{\"u}rgen and Rhede, Dieter}, title = {The Be-Ta-rich granite of Seiffen (eastern Erzgebirge, Germany)}, series = {Neues Jahrbuch f{\"u}r Mineralogie : Abhandlungen}, volume = {182}, journal = {Neues Jahrbuch f{\"u}r Mineralogie : Abhandlungen}, number = {3}, publisher = {Schweizerbart}, address = {Stuttgart}, issn = {0077-7757}, doi = {10.1127/0077-7757/2006/0055}, pages = {307 -- 321}, year = {2006}, abstract = {The mildly peraluminous granite of Seiffen, in the eastern Erzgebirge of Germany, is exposed by drillcores and associated with an abandoned Sri mine. The granite is of Stefanian age, with overlapping Th-U-total Pb monazite (302 +/- 4 Ma) and K-Ar siderophyllite ages (301 +/- 5 Ma). It is among the youngest granites in the Erzgebirge, emplaced in an extensional setting. The medium-grained, equigranular granite classifies as high-F, low-P Li-mica granite of A-type affinity. It is spatially associated with a high-Si rhyolitic microgranite, documenting the shallow intrusion level of this igneous association. Zircon, monazite-(Ce), and xenotime-(Y) constitute important radioactive accessory minerals in the granite, hosting the major proportions (> 80-90\%) of the bulk-rock budgets of the REE, Y, and Th. A significant percentage of U (40-50\%) may reside within unidentified phases or precipitated along grain boundaries. The most uncommon accessory phase is late-magmatic ytterbian xenotime-(Y) containing up to 11.2 wt\% Yb2O3, in addition to 7.3 wt\% Er2O3 and 7.9 wt\% Dy2O3. The Seiffen granite (epsilon(Nd(300)) = -4.6) is geochemically evolved and rich in Sri (23-63 ppm) and W (11-14 ppm). It contains elevated to high concentrations of incompatible lithophile elements such as F, Li, Ga, Rb, Y, Nb, Cs, REE, Th, and U, thus having much in common chemically with subvolcanic ongonites. The most prominent compositional feature is the strong enrichment (in ppm) in Be (51-55) and Ta (23-28). The granite exhibits flat chondrite-normalized REE patterns (La-N/Lu-N = 1.35-1.48) and a moderate negative Eu anomaly (Eu/Eu* = 0.12-0.13). Indications for alteration-induced, postmagmatic disturbances of initial elemental abundances are weak and mainly relate to the ore-forming elements Sri and U.}, language = {en} } @article{BufeTurowskiBurbanketal.2019, author = {Bufe, Aaron and Turowski, Jens M. and Burbank, Douglas W. and Paola, Chris and Wickert, Andrew D. and Tofelde, Stefanie}, title = {Controls on the lateral channel-migration rate of braided channel systems in coarse non-cohesive sediment}, series = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group}, volume = {44}, journal = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group}, number = {14}, publisher = {Wiley}, address = {Hoboken}, issn = {0197-9337}, doi = {10.1002/esp.4710}, pages = {2823 -- 2836}, year = {2019}, abstract = {Lateral movements of alluvial river channels control the extent and reworking rates of alluvial fans, floodplains, deltas, and alluvial sections of bedrock rivers. These lateral movements can occur by gradual channel migration or by sudden changes in channel position (avulsions). Whereas models exist for rates of river avulsion, we lack a detailed understanding of the rates of lateral channel migration on the scale of a channel belt. In a two-step process, we develop here an expression for the lateral migration rate of braided channel systems in coarse, non-cohesive sediment. On the basis of photographic and topographic data from laboratory experiments of braided channels performed under constant external boundary conditions, we first explore the impact of autogenic variations of the channel-system geometry (i.e. channel-bank heights, water depths, channel-system width, and channel slope) on channel-migration rates. In agreement with theoretical expectations, we find that, under such constant boundary conditions, the laterally reworked volume of sediment is constant and lateral channel-migration rates scale inversely with the channel-bank height. Furthermore, when channel-bank heights are accounted for, lateral migration rates are independent of the remaining channel geometry parameters. These constraints allow us, in a second step, to derive two alternative expressions for lateral channel-migration rates under different boundary conditions using dimensional analysis. Fits of a compilation of laboratory experiments to these expressions suggest that, for a given channel bank-height, migration rates are strongly sensitive to water discharges and more weakly sensitive to sediment discharges. In addition, external perturbations, such as changes in sediment and water discharges or base level fall, can indirectly affect lateral channel-migration rates by modulating channel-bank heights.}, language = {en} } @article{CarvalhoBartoliFerrietal.2019, author = {Carvalho, Bruna B. and Bartoli, Omar and Ferri, Fabio and Cesare, Bernardo and Ferrero, Silvio and Remusat, Laurent and Capizzi, Luca Samuele and Poli, Stefano}, title = {Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)}, series = {Journal of metamorphic geology}, volume = {37}, journal = {Journal of metamorphic geology}, number = {7}, publisher = {Wiley}, address = {Hoboken}, issn = {0263-4929}, doi = {10.1111/jmg.12463}, pages = {951 -- 975}, year = {2019}, abstract = {We investigate the inclusions hosted in peritectic garnet from metapelitic migmatites of the Kinzigite Formation (Ivrea Zone, NW Italy) to evaluate the starting composition of the anatectic melt and fluid regime during anatexis throughout the upper amphibolite facies, transition, and granulite facies zones. Inclusions have negative crystal shapes, sizes from 2 to 10 mu m and are regularly distributed in the core of the garnet. Microstructural and micro-Raman investigations indicate the presence of two types of inclusions: crystallized silicate melt inclusions (i.e., nanogranitoids, NI), and fluid inclusions (FI). Microstructural evidence suggests that FI and NI coexist in the same cluster and are primary (i.e., were trapped simultaneously during garnet growth). FI have similar compositions in the three zones and comprise variable proportions of CO2, CH4, and N-2, commonly with siderite, pyrophyllite, and kaolinite, suggesting a COHN composition of the trapped fluid. The mineral assemblage in the NI contains K-feldspar, plagioclase, quartz, biotite, muscovite, chlorite, graphite and, rarely, calcite. Polymorphs such as kumdykolite, cristobalite, tridymite, and less commonly kokchetavite, were also found. Rehomogenized NI from the different zones show that all the melts are leucogranitic but have slightly different compositions. In samples from the upper amphibolite facies, melts are less mafic (FeO + MgO = 2.0-3.4 wt\%), contain 860-1700 ppm CO2 and reach the highest H2O contents (6.5-10 wt\%). In the transition zone melts have intermediate H2O (4.8-8.5 wt\%), CO2 (457-1534 ppm) and maficity (FeO + MgO = 2.3-3.9 wt\%). In contrast, melts at granulite facies reach highest CaO, FeO + MgO (3.2-4.7 wt\%), and CO2 (up to 2,400 ppm), with H2O contents comparable (5.4-8.3 wt\%) to the other two zones. Our results represent the first clear evidence for carbonic fluid-present melting in the Ivrea Zone. Anatexis of metapelites occurred through muscovite and biotite breakdown melting in the presence of a COH fluid, in a situation of fluid-melt immiscibility. The fluid is assumed to have been internally derived, produced initially by devolatilization of hydrous silicates in the graphitic protolith, then as a result of oxidation of carbon by consumption of Fe3+-bearing biotite during melting. Variations in the compositions of the melts are interpreted to result from higher T of melting. The H2O contents of the melts throughout the three zones are higher than usually assumed for initial H2O contents of anatectic melts. The CO2 contents are highest at granulite facies, and show that carbon-contents of crustal magmas are not negligible at high T. The activity of H2O of the fluid dissolved in granitic melts decreases with increasing metamorphic grade. Carbonic fluid-present melting of the deep continental crust represents, together with hydrate-breakdown melting reactions, an important process in the origin of crustal anatectic granitoids.}, language = {en} } @book{RahmstorfSchellnhuber2020, author = {Rahmstorf, Stefan and Schellnhuber, Hans Joachim}, title = {Der Klimawandel}, series = {Schriftenreihe / Bundeszentrale f{\"u}r politische Bildung ; Band 10520}, journal = {Schriftenreihe / Bundeszentrale f{\"u}r politische Bildung ; Band 10520}, publisher = {Bundeszentrale f{\"u}r politische Bildung}, address = {Bonn}, isbn = {978-3-7425-0520-0}, pages = {144}, year = {2020}, language = {de} } @article{Ziemann2006, author = {Ziemann, Martin Andreas}, title = {In situ micro-Raman spectroscopy on minerals on-site in the Grotto Hall of the New Palace, Park Sanssouci, in Potsdam}, series = {Journal of Raman spectroscopy : JRS}, volume = {37}, journal = {Journal of Raman spectroscopy : JRS}, number = {10}, publisher = {Wiley}, address = {Chichester}, issn = {0377-0486}, doi = {10.1002/jrs.1584}, pages = {1019 -- 1025}, year = {2006}, abstract = {Questions of identity and provenance of minerals that are parts of masterpieces in museums have become increasingly important in mineralogical and historical studies. Detailed investigations of valuable and unique objects require on-site, nondestructive and noninvasive methods because touching or removing them may cause irreparable damage. A mobile Raman-microprobe has been used to meet these demands for truly in situ mineralogical studies of the large collection of minerals and rocks of the Prussian kings in the Grotto Hall (Grottensaal) of the New Palace (Neues Palais), Park Sanssouci in Potsdam. Minerals on the walls of the Grotto Hall were analyzed to identify them and thereby to complete the data bank of the collection. Fluid and solid inclusions in the interior of a large quartz crystal have been studied to provide evidence of the provenance of the crystal. The fluid inclusions contain aqueous saline solutions, whereas the solid inclusions are needles of anhydrite with a length of about 1.5 mm. The quartz probably originated from an area in the eastern Alps, from the surroundings of Bad Gastein, Austria. This is the first on-site and in situ study of inclusions below the surface of a mineral with a mobile Raman-microprobe outside a laboratory.}, language = {en} } @article{ThomasWebsterRhedeetal.2006, author = {Thomas, Rainer and Webster, J. D. and Rhede, Dieter and Seifert, W. and Rickers, Karen and F{\"o}rster, Hans-J{\"u}rgen and Heinrich, Wilhelm and Davidson, P.}, title = {The transition from peraluminous to peralkaline granitic melts: Evidence from melt inclusions and accessory minerals}, series = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, volume = {91}, journal = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, number = {1-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0024-4937}, doi = {10.1016/j.lithos.2006.03.013}, pages = {137 -- 149}, year = {2006}, abstract = {Fractional crystallization of peraluminous F- and H(2)O-rich granite magmas progressively enriches the remaining melt with volatiles. We show that, at saturation, the melt may separate into two immiscible conjugate melt fractions, one of the fractions shows increasing peraluminosity and the other increasing peralkalinity. These melt fractions also fractionate the incompatible elements to significantly different degrees. Coexisting melt fractions have differing chemical and physical properties and, due to their high density and viscosity contrasts, they will tend to separate readily from each other. Once separated, each melt fraction evolves independently in response to changing T/P/X conditions and further immiscibility events may occur, each generating its own conjugate pair of melt fractions. The strongly peralkaline melt fractions in particular are very reactive and commonly react until equilibrium is attained. Consequently, the peralkaline melt fraction is commonly preserved only in the isolated melt and mineral inclusions. We demonstrate that the differences between melt fractions that can be seen most clearly in differing melt inclusion compositions are also visible in the composition of the resulting ore-forming and accessory minerals, and are visible on scales from a few micrometers to hundreds of meters.}, language = {en} } @article{KnudsenHeinoldDahlkeetal.2018, author = {Knudsen, Erlend Moster and Heinold, Bernd and Dahlke, Sandro and Bozem, Heiko and Crewell, Susanne and Gorodetskaya, Irina V. and Heygster, Georg and Kunkel, Daniel and Maturilli, Marion and Mech, Mario and Viceto, Carolina and Rinke, Annette and Schmithusen, Holger and Ehrlich, Andre and Macke, Andreas and L{\"u}pkes, Christof and Wendisch, Manfred}, title = {Meteorological conditions during the ACLOUD/PASCAL field campaign near Svalbard in early summer 2017}, series = {Atmospheric chemistry and physics}, volume = {18}, journal = {Atmospheric chemistry and physics}, number = {24}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1680-7316}, doi = {10.5194/acp-18-17995-2018}, pages = {17995 -- 18022}, year = {2018}, abstract = {The two concerted field campaigns, Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) and the Physical feedbacks of Arctic planetary boundary level Sea ice, Cloud and AerosoL (PASCAL), took place near Svalbard from 23 May to 26 June 2017. They were focused on studying Arctic mixed-phase clouds and involved observations from two airplanes (ACLOUD), an icebreaker (PASCAL) and a tethered balloon, as well as ground-based stations. Here, we present the synoptic development during the 35-day period of the campaigns, using near-surface and upper-air meteorological observations, as well as operational satellite, analysis, and reanalysis data. Over the campaign period, short-term synoptic variability was substantial, dominating over the seasonal cycle. During the first campaign week, cold and dry Arctic air from the north persisted, with a distinct but seasonally unusual cold air outbreak. Cloudy conditions with mostly low-level clouds prevailed. The subsequent 2 weeks were characterized by warm and moist maritime air from the south and east, which included two events of warm air advection. These synoptical disturbances caused lower cloud cover fractions and higher-reaching cloud systems. In the final 2 weeks, adiabatically warmed air from the west dominated, with cloud properties strongly varying within the range of the two other periods. Results presented here provide synoptic information needed to analyze and interpret data of upcoming studies from ACLOUD/PASCAL, while also offering unprecedented measurements in a sparsely observed region.}, language = {en} } @article{BoessenkoolBuergerHeistermann2017, author = {B{\"o}ssenkool, Berry and B{\"u}rger, Gerd and Heistermann, Maik}, title = {Effects of sample size on estimation of rainfall extremes at high temperatures}, series = {Natural hazards and earth system sciences}, volume = {17}, journal = {Natural hazards and earth system sciences}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1561-8633}, doi = {10.5194/nhess-17-1623-2017}, pages = {1623 -- 1629}, year = {2017}, abstract = {High precipitation quantiles tend to rise with temperature, following the so-called Clausius-Clapeyron (CC) scaling. It is often reported that the CC-scaling relation breaks down and even reverts for very high temperatures. In our study, we investigate this reversal using observational climate data from 142 stations across Germany. One of the suggested meteorological explanations for the breakdown is limited moisture supply. Here we argue that, instead, it could simply originate from undersampling. As rainfall frequency generally decreases with higher temperatures, rainfall intensities as dictated by CC scaling are less likely to be recorded than for moderate temperatures. Empirical quantiles are conventionally estimated from order statistics via various forms of plotting position formulas. They have in common that their largest representable return period is given by the sample size. In small samples, high quantiles are underestimated accordingly. The small-sample effect is weaker, or disappears completely, when using parametric quantile estimates from a generalized Pareto distribution (GPD) fitted with L moments. For those, we obtain quantiles of rainfall intensities that continue to rise with temperature.}, language = {en} } @misc{KnapmeyerEndrunGolombekOhrnberger2017, author = {Knapmeyer-Endrun, Brigitte and Golombek, Matthew P. and Ohrnberger, Matthias}, title = {Rayleigh Wave Ellipticity Modeling and Inversion for Shallow Structure at the Proposed InSight Landing Site in Elysium Planitia, Mars}, series = {Space science reviews}, volume = {211}, journal = {Space science reviews}, publisher = {Springer}, address = {Dordrecht}, issn = {0038-6308}, doi = {10.1007/s11214-016-0300-1}, pages = {339 -- 382}, year = {2017}, abstract = {The SEIS (Seismic Experiment for Interior Structure) instrument onboard the InSight mission will be the first seismometer directly deployed on the surface of Mars. From studies on the Earth and the Moon, it is well known that site amplification in low-velocity sediments on top of more competent rocks has a strong influence on seismic signals, but can also be used to constrain the subsurface structure. Here we simulate ambient vibration wavefields in a model of the shallow sub-surface at the InSight landing site in Elysium Planitia and demonstrate how the high-frequency Rayleigh wave ellipticity can be extracted from these data and inverted for shallow structure. We find that, depending on model parameters, higher mode ellipticity information can be extracted from single-station data, which significantly reduces uncertainties in inversion. Though the data are most sensitive to properties of the upper-most layer and show a strong trade-off between layer depth and velocity, it is possible to estimate the velocity and thickness of the sub-regolith layer by using reasonable constraints on regolith properties. Model parameters are best constrained if either higher mode data can be used or additional constraints on regolith properties from seismic analysis of the hammer strokes of InSight's heat flow probe HP3 are available. In addition, the Rayleigh wave ellipticity can distinguish between models with a constant regolith velocity and models with a velocity increase in the regolith, information which is difficult to obtain otherwise.}, language = {en} } @article{BaumbachSiegmundMittermeieretal.2017, author = {Baumbach, Lukas and Siegmund, Jonatan F. and Mittermeier, Magdalena and Donner, Reik Volker}, title = {Impacts of temperature extremes on European vegetation during the growing season}, series = {Biogeosciences}, volume = {14}, journal = {Biogeosciences}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1726-4170}, doi = {10.5194/bg-14-4891-2017}, pages = {4891 -- 4903}, year = {2017}, abstract = {Temperature is a key factor controlling plant growth and vitality in the temperate climates of the mid-latitudes like in vast parts of the European continent. Beyond the effect of average conditions, the timings and magnitudes of temperature extremes play a particularly crucial role, which needs to be better understood in the context of projected future rises in the frequency and/or intensity of such events. In this work, we employ event coincidence analysis (ECA) to quantify the likelihood of simultaneous occurrences of extremes in daytime land surface temperature anomalies (LSTAD) and the normalized difference vegetation index (NDVI). We perform this analysis for entire Europe based upon remote sensing data, differentiating between three periods corresponding to different stages of plant development during the growing season. In addition, we analyze the typical elevation and land cover type of the regions showing significantly large event coincidences rates to identify the most severely affected vegetation types. Our results reveal distinct spatio-temporal impact patterns in terms of extraordinarily large co-occurrence rates between several combinations of temperature and NDVI extremes. Croplands are among the most frequently affected land cover types, while elevation is found to have only a minor effect on the spatial distribution of corresponding extreme weather impacts. These findings provide important insights into the vulnerability of European terrestrial ecosystems to extreme temperature events and demonstrate how event-based statistics like ECA can provide a valuable perspective on environmental nexuses.}, language = {en} } @article{AichnerHiltPerillonetal.2017, author = {Aichner, Bernhard and Hilt, Sabine and Perillon, Cecile and Gillefalk, Mikael and Sachse, Dirk}, title = {Biosynthetic hydrogen isotopic fractionation factors during lipid synthesis in submerged aquatic macrophytes: Effect of groundwater discharge and salinity}, series = {Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry}, volume = {113}, journal = {Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry}, publisher = {Elsevier}, address = {Oxford}, issn = {0146-6380}, doi = {10.1016/j.orggeochem.2017.07.021}, pages = {10 -- 16}, year = {2017}, abstract = {Sedimentary lipid biomarkers have become widely used tools for reconstructing past climatic and ecological changes due to their ubiquitous occurrence in lake sediments. In particular, the hydrogen isotopic composition (expressed as delta D values) of leaf wax lipids derived from terrestrial plants has been a focus of research during the last two decades and the understanding of competing environmental and plant physiological factors influencing the delta D values has greatly improved. Comparatively less attention has been paid to lipid biomarkers derived from aquatic plants, although these compounds are abundant in many lacustrine sediments. We therefore conducted a field and laboratory experiment to study the effect of salinity and groundwater discharge on the isotopic composition of aquatic plant biomarkers. We analyzed samples of the common submerged plant species, Potamogeton pectinatus (sago pondweed), which has a wide geographic distribution and can tolerate high salinity. We tested the effect of groundwater discharge (characterized by more negative delta D values relative to lake water) and salinity on the delta D values of n-alkanes from P. pectinatus by comparing plants (i) collected from the oligotrophic freshwater Lake Stechlin (Germany) at shallow littoral depth from locations with and without groundwater discharge, and (ii) plants grown from tubers collected from the eutrophic Lake Muggelsee in nutrient solution at four salinity levels. Isotopically depleted groundwater did not have a significant influence on the delta D values of n-alkanes in Lake Stechlin P. pectinatus and calculated isotopic fractionation factors epsilon(l/w) between lake water and n-alkanes averaged -137 +/- 9\%(n-C-23), -136 +/- 7\%(n-C-25) and -131 +/- 6\%(n-C-27), respectively. Similar epsilon values were calculated for plants from Lake Muggelsee grown in freshwater nutrient solution (-134 +/- 11\% for n-C-23), while greater fractionation was observed at increased salinity values of 10 (163 +/- 12\%) and 15(-172 +/- 15\%). We therefore suggest an average e value of -136 +/- 9\% between source water and the major n-alkanes in P. pectinatus grown under freshwater conditions. Our results demonstrate that isotopic fractionation can increase by 30-40\% at salinity values 10 and 15. These results could be explained either by inhibited plant growth at higher salinity, or by metabolic adaptation to salt stress that remain to be elucidated. A potential salinity effect on dD values of aquatic lipids requires further examination, since this would impact on the interpretation of downcore isotopic data in paleohydrologic studies. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{BruneCortiRanalli2017, author = {Brune, Sascha and Corti, Giacomo and Ranalli, Giorgio}, title = {Controls of inherited lithospheric heterogeneity on rift linkage: Numerical and analog models of interaction between the Kenyan and Ethiopian rifts across the Turkana depression}, series = {Tectonics}, volume = {36}, journal = {Tectonics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0278-7407}, doi = {10.1002/2017TC004739}, pages = {1767 -- 1786}, year = {2017}, abstract = {Inherited rheological structures in the lithosphere are expected to have large impact on the architecture of continental rifts. The Turkana depression in the East African Rift connects the Main Ethiopian Rift to the north with the Kenya rift in the south. This region is characterized by a NW-SE trending band of thinned crust inherited from a Mesozoic rifting event, which is cutting the present-day N-S rift trend at high angle. In striking contrast to the narrow rifts in Ethiopia and Kenya, extension in the Turkana region is accommodated in subparallel deformation domains that are laterally distributed over several hundred kilometers. We present both analog experiments and numerical models that reproduce the along-axis transition from narrow rifting in Ethiopia and Kenya to a distributed deformation within the Turkana depression. Similarly to natural observations, our models show that the Ethiopian and Kenyan rifts bend away from each other within the Turkana region, thus forming a right-lateral step over and avoiding a direct link to form a continuous N-S depression. The models reveal five potential types of rift linkage across the preexisting basin: three types where rifts bend away from the inherited structure connecting via a (1) wide or (2) narrow rift or by (3) forming a rotating microplate, (4) a type where rifts bend towards it, and (5) straight rift linkage. The fact that linkage type 1 is realized in the Turkana region provides new insights on the rheological configuration of the Mesozoic rift system at the onset of the recent rift episode. Plain Language Summary The Turkana depression in the Kenya/Ethiopia borderland is most famous for its several million years old human fossils, but it also holds a rich geological history of continental separation. The Turkana region is a lowland located between the East African and Ethiopian domes because its crust and mantle have been stretched in a continent-wide rift event during Cretaceous times about 140-120 Ma ago. This thin lithosphere exerted paramount control on the dynamics of East African rifting in this area, which commenced around 15 Ma ago and persists until today. Combining analog "sandbox" experiments with numerical geodynamic modeling, we find that inherited rift structures explain the dramatic change in rift style from deep, narrow rift basins north and south of the Turkana area to wide, distributed deformation within the Turkana depression. The failed Cretaceous rift is also responsible for the eastward bend of the Ethiopian rift and the westward bend of the Kenyan rift when entering the Turkana depression, which generated the characteristic hook-shaped form of present-day Lake Turkana. Combing two independent modeling techniques-analog and numerical experiments-is a very promising approach allowing to draw robust conclusions about the processes that shape the surface of our planet.}, language = {en} } @article{BoersGoswamiGhil2017, author = {Boers, Niklas and Goswami, Bedartha and Ghil, Michael}, title = {A complete representation of uncertainties in layer-counted paleoclimatic archives}, series = {Climate of the past : an interactive open access journal of the European Geosciences Union}, volume = {13}, journal = {Climate of the past : an interactive open access journal of the European Geosciences Union}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1814-9324}, doi = {10.5194/cp-13-1169-2017}, pages = {12}, year = {2017}, abstract = {Accurate time series representation of paleoclimatic proxy records is challenging because such records involve dating errors in addition to proxy measurement errors. Rigorous attention is rarely given to age uncertainties in paleoclimatic research, although the latter can severely bias the results of proxy record analysis. Here, we introduce a Bayesian approach to represent layer-counted proxy records - such as ice cores, sediments, corals, or tree rings - as sequences of probability distributions on absolute, error-free time axes. The method accounts for both proxy measurement errors and uncertainties arising from layer-counting-based dating of the records. An application to oxygen isotope ratios from the North Greenland Ice Core Project (NGRIP) record reveals that the counting errors, although seemingly small, lead to substantial uncertainties in the final representation of the oxygen isotope ratios. In particular, for the older parts of the NGRIP record, our results show that the total uncertainty originating from dating errors has been seriously underestimated. Our method is next applied to deriving the overall uncertainties of the Suigetsu radiocarbon comparison curve, which was recently obtained from varved sediment cores at Lake Suigetsu, Japan. This curve provides the only terrestrial radiocarbon comparison for the time interval 12.5-52.8 kyr BP. The uncertainties derived here can be readily employed to obtain complete error estimates for arbitrary radiometrically dated proxy records of this recent part of the last glacial interval.}, language = {en} } @article{RachEngelsKahmenetal.2017, author = {Rach, Oliver and Engels, S. and Kahmen, A. and Brauer, Achim and Martin-Puertas, C. and van Geel, B. and Sachse, Dirk}, title = {Hydrological and ecological changes in western Europe between 3200 and 2000 years BP derived from lipid biomarker delta D values in lake Meerfelder Maar sediments}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {172}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.07.019}, pages = {44 -- 54}, year = {2017}, abstract = {One of the most significant Late Holocene climate shifts occurred around 2800 years ago, when cooler and wetter climate conditions established in western Europe. This shift coincided with an abrupt change in regional atmospheric circulation between 2760 and 2560 cal years BP, which has been linked to a grand solar minimum with the same duration (the Homeric Minimum). We investigated the temporal sequence of hydroclimatic and vegetation changes across this interval of climatic change (Homeric climate oscillation) by using lipid biomarker stable hydrogen isotope ratios (ED values) and pollen assemblages from the annually-laminated sediment record from lake Meerfelder Maar (Germany). Over the investigated interval (3200-2000 varve years BP), terrestrial lipid biomarker ED showed a gradual trend to more negative values, consistent with the western Europe long-term climate trend of the Late Holocene. At ca. 2640 varve years BP we identified a strong increase in aquatic plants and algal remains, indicating a rapid change in the aquatic ecosystem superimposed on this long-term trend. Interestingly, this aquatic ecosystem change was accompanied by large changes in ED values of aquatic lipid biomarkers, such as nC(21) and nC(23) (by between 22 and 30\%(0)). As these variations cannot solely be explained by hydroclimate changes, we suggest that these changes in the Wag value were influenced by changes in n-alkane source organisms. Our results illustrate that if ubiquitous aquatic lipid biomarkers are derived from a limited pool of organisms, changes in lake ecology can be a driving factor for variations on sedimentary lipid MN values, which then could be easily misinterpreted in terms of hydro climatic changes. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{RubeyBruneHeineetal.2017, author = {Rubey, Michael and Brune, Sascha and Heine, Christian and Davies, D. Rhodri and Williams, Simon E. and M{\"u}ller, R. Dietmar}, title = {role of subducted slabs}, series = {Solid earth}, volume = {8}, journal = {Solid earth}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1869-9510}, doi = {10.5194/se-8-899-2017}, pages = {899 -- 919}, year = {2017}, language = {en} } @article{Buerger2017, author = {B{\"u}rger, Gerhard}, title = {On trend detection}, series = {Hydrological processes}, volume = {31}, journal = {Hydrological processes}, publisher = {Wiley}, address = {Hoboken}, issn = {0885-6087}, doi = {10.1002/hyp.11280}, pages = {4039 -- 4042}, year = {2017}, abstract = {A main obstacle to trend detection in time series occurs when they are autocorrelated. By reducing the effective sample size of a series, autocorrelation leads to decreased trend significance. Numerous recipes attempt to mitigate the effect of autocorrelation, either by adjusting for the reduced effective sample size or by removing the autocorrelated components of a series. This short note deals with the latter, also called prewhitening (PW). It is known that removal of autocorrelation also removes part of the trend, which may affect the signal-to-noise ratio. Two popular methods have dealt with this problem, the trend-free prewhitening (TFPW) and the iterative prewhitening. Although it is generally accepted that both methods reduce the adverse effects of PW on the trend magnitude, corresponding effects on statistical significance have not been clearly stated for TFPW. Using a Monte Carlo approach, it is demonstrated that both methods entail quite different Type-I error rates. The iterative prewhitening produces rates that are generally close to the nominal significance level. The TFPW, however, shows very high Type-I error rates with increasing autocorrelation. The corresponding rate of false trend detections is unacceptable for applications, so that published trends based on TFPW need to be reassessed.}, language = {en} } @article{NazarovaBleibtreuHoffetal.2017, author = {Nazarova, Larisa B. and Bleibtreu, Annette and Hoff, Ulrike and Dirksen, Veronika and Diekmann, Bernhard}, title = {Changes in temperature and water depth of a small mountain lake during the past 3000 years in Central Kamchatka reflected by a chironomid record}, series = {Quaternary international : the journal of the International Union for Quaternary Research}, volume = {447}, journal = {Quaternary international : the journal of the International Union for Quaternary Research}, publisher = {Elsevier}, address = {Oxford}, issn = {1040-6182}, doi = {10.1016/j.quaint.2016.10.008}, pages = {46 -- 58}, year = {2017}, abstract = {We investigated chironomid assemblages of a well-dated sediment core from a small seepage lake situated at the eastern slope of the Central Kamchatka Mountain Chain, Far East Russia. The chironomid fauna of the investigated Sigrid Lake is dominated by littoral taxa that are sensitive to fluctuations of the water level. Two groups of taxa interchangeably dominate the record responding to the changes in the lake environment during the past 2800 years. The first group of littoral phytophilic taxa includes Psectrocladius sordidellus-type, Corynoneura arctica-type and Dicrotendipes nervosus-type. The abundances of the taxa from this group have the strongest influence on the variations of PCA 1, and these taxa mostly correspond to low water levels, moderate temperatures and slightly acidified conditions. The second group of taxa includes Microtendipes pedellus-type, Tanytarsus lugens-type, and Tanytarsus pallidicornistype. The variations in the abundances of these taxa, and especially of M. pedellus-type, are in accordance with PCA 2 and correspond to the higher water level in the lake, more oligotrophic and neutral pH conditions. Water depths (WD) were reconstructed, using a modern chironomid-based temperature and water depth calibration data set (training set) and inference model from East Siberia (Nazarova et al., 2011). Mean July air temperatures (T July) were inferred using a chironomid-based temperature inference model based on a modern calibration data set for the Far East (Nazarova et al., 2015). The application of transfer functions resulted in reconstructed T July fluctuations of approximately 3 degrees C over the last 2800 years. Low temperatures (11.0-12.0 degrees C) were reconstructed for the periods between ca 1700 and 1500 cal yr BP (corresponding to the Kofun cold stage) and between ca 1200 and 150 cal yr BP (partly corresponding to the Little Ice Age [LIA]). Warm periods (modern T July or higher) were reconstructed for the periods between ca 2700 and 1800 cal yr BP, 1500 and 1300 cal yr BP and after 150 cal yr BP. WD reconstruction revealed that the lake level was lower than its present level at the beginning of the record between ca 2600 and 2300 cal yr BP and ca 550 cal yr BP. Between ca 2300 and 700 cal yr BP as well as between 450 and 150 cal yr BP, the lake level was higher than it is today, most probably reflecting more humid conditions. (C) 2016 Elsevier Ltd and INQUA. All rights reserved.}, language = {en} } @article{MarkovicCarrizoKaercheretal.2017, author = {Markovic, Danijela and Carrizo, Savrina F. and Kaercher, Oskar and Walz, Ariane and David, Jonathan N. W.}, title = {Vulnerability of European freshwater catchments to climate change}, series = {Global change biology}, volume = {23}, journal = {Global change biology}, publisher = {Wiley}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/gcb.13657}, pages = {3567 -- 3580}, year = {2017}, abstract = {Climate change is expected to exacerbate the current threats to freshwater ecosystems, yet multifaceted studies on the potential impacts of climate change on freshwater biodiversity at scales that inform management planning are lacking. The aim of this study was to fill this void through the development of a novel framework for assessing climate change vulnerability tailored to freshwater ecosystems. The three dimensions of climate change vulnerability are as follows: (i) exposure to climate change, (ii) sensitivity to altered environmental conditions and (iii) resilience potential. Our vulnerability framework includes 1685 freshwater species of plants, fishes, molluscs, odonates, amphibians, crayfish and turtles alongside key features within and between catchments, such as topography and connectivity. Several methodologies were used to combine these dimensions across a variety of future climate change models and scenarios. The resulting indices were overlaid to assess the vulnerability of European freshwater ecosystems at the catchment scale (18 783 catchments). The Balkan Lakes Ohrid and Prespa and Mediterranean islands emerge as most vulnerable to climate change. For the 2030s, we showed a consensus among the applied methods whereby up to 573 lake and river catchments are highly vulnerable to climate change. The anthropogenic disruption of hydrological habitat connectivity by dams is the major factor reducing climate change resilience. A gap analysis demonstrated that the current European protected area network covers <25\% of the most vulnerable catchments. Practical steps need to be taken to ensure the persistence of freshwater biodiversity under climate change. Priority should be placed on enhancing stakeholder cooperation at the major basin scale towards preventing further degradation of freshwater ecosystems and maintaining connectivity among catchments. The catchments identified as most vulnerable to climate change provide preliminary targets for development of climate change conservation management and mitigation strategies.}, language = {en} } @article{EgholmJansenBraedstrupetal.2017, author = {Egholm, David L. and Jansen, John D. and Braedstrup, Christian F. and Pedersen, Vivi K. and Andersen, Jane Lund and Ugelvig, Sofie V. and Larsen, Nicolaj K. and Knudsen, Mads F.}, title = {Formation of plateau landscapes on glaciated continental margins}, series = {Nature geoscience}, volume = {10}, journal = {Nature geoscience}, publisher = {Nature Publ. Group}, address = {New York}, issn = {1752-0894}, doi = {10.1038/NGEO2980}, pages = {592 -- +}, year = {2017}, abstract = {Low-relief plateaus separated by deeply incised fjords are hallmarks of glaciated, passive continental margins. Spectacular examples fringe the once ice-covered North Atlantic coasts of Greenland, Norway and Canada, but low-relief plateau landscapes also underlie present-day ice sheets in Antarctica and Greenland. Dissected plateaus have long been viewed as the outcome of selective linear erosion by ice sheets that focus incision in glacial troughs, leaving the intervening landscapes essentially unaffected. According to this hypothesis, the plateaus are remnants of preglacial low-relief topography. However, here we use computational experiments to show that, like fjords, plateaus are emergent properties of long-term ice-sheet erosion. Ice sheets can either increase or decrease subglacial relief depending on the wavelength of the underlying topography, and plateau topography arises dynamically from evolving feedbacks between topography, ice dynamics and erosion over million-year timescales. This new mechanistic explanation for plateau formation opens the possibility of plateaus contributing significantly to accelerated sediment flux at the onset of the late Cenozoic glaciations, before becoming stable later in the Quaternary.}, language = {en} } @article{NeillJankowskiBrandoetal.2017, author = {Neill, Christopher and Jankowski, KathiJo and Brando, Paulo M. and Coe, Michael T. and Deegan, Linda A. and Macedo, Marcia N. and Riskin, Shelby H. and Porder, Stephen and Elsenbeer, Helmut and Krusche, Alex V.}, title = {Surprisingly Modest Water Quality Impacts From Expansion and Intensification of Large-Sscale Commercial Agriculture in the Brazilian Amazon-Cerrado Region}, series = {Tropical conservation science}, volume = {10}, journal = {Tropical conservation science}, publisher = {Sage Publ.}, address = {Thousand Oaks}, issn = {1940-0829}, doi = {10.1177/1940082917720669}, pages = {5}, year = {2017}, abstract = {Large-scale commercial cropping of soybeans expanded in the tropical Amazon and Cerrado biomes of Brazil after 1990. More recently, cropping intensified from single-cropping of soybeans to double-cropping of soybeans with corn or cotton. Cropland expansion and intensification, and the accompanying use of mineral fertilizers, raise concerns about whether nutrient runoff and impacts to surface waters will be similar to those experienced in commercial cropland regions at temperate latitudes. We quantified water infiltration through soils, water yield, and streamwater chemistry in watersheds draining native tropical forest and single-and double-cropped areas on the level, deep, highly weathered soils where cropland expansion and intensification typically occurs. Although water yield increased four-fold from croplands, streamwater chemistry remained largely unchanged. Soil characteristics exerted important control over the movement of nitrogen (N) and phosphorus (P) into streams. High soil infiltration rates prevented surface erosion and movement of particulate P, while P fixation in surface soils restricted P movement to deeper soil layers. Nitrogen retention in deep soils, likely by anion exchange, also appeared to limit N leaching and export in streamwater from both single-and double-cropped watersheds that received nitrogen fertilizer. These mechanisms led to lower streamwater P and N concentrations and lower watershed N and P export than would be expected, based on studies from temperate croplands with similar cropping and fertilizer application practices.}, language = {en} } @article{StinnesbeckBeckerHeringetal.2017, author = {Stinnesbeck, Wolfgang and Becker, Julia and Hering, Fabio and Frey, Eberhard and Gonzalez Gonzalez, Arturo and Fohlmeister, Jens Bernd and Stinnesbeck, Sarah and Frank, Norbert and Terrazas Mata, Alejandro and Elena Benavente, Martha and Aviles Olguin, Jeronimo and Aceves Nunez, Eugenio and Zell, Patrick and Deininger, Michael}, title = {The earliest settlers of Mesoamerica date back to the late Pleistocene}, series = {PLoS one}, volume = {12}, journal = {PLoS one}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0183345}, pages = {20}, year = {2017}, abstract = {Preceramic human skeletal remains preserved in submerged caves near Tulum in the Mexican state of Quintana Roo, Mexico, reveal conflicting results regarding C-14 dating. Here we use U-series techniques for dating a stalagmite overgrowing the pelvis of a human skeleton discovered in the submerged Chan Hol cave. The oldest closed system U/Th age comes from around 21 mm above the pelvis defining the terminus ante quem for the pelvis to 11311 +/- 370 y BP. However, the skeleton might be considerable older, probably as old as 13 ky BP as indicated by the speleothem stable isotope data. The Chan Hol individual confirms a late Pleistocene settling of Mesoamerica and represents one of the oldest human osteological remains in America.}, language = {en} } @article{KornhuberPetoukhovKarolyetal.2017, author = {Kornhuber, Kai and Petoukhov, Vladimir and Karoly, D. and Petri, Stefan and Rahmstorf, Stefan and Coumou, Dim}, title = {Summertime Planetary Wave Resonance in the Northern and Southern Hemispheres}, series = {Journal of climate}, volume = {30}, journal = {Journal of climate}, publisher = {American Meteorological Soc.}, address = {Boston}, issn = {0894-8755}, doi = {10.1175/JCLI-D-16-0703.1}, pages = {6133 -- 6150}, year = {2017}, language = {en} } @article{SchmidtWalzMartinLopezetal.2017, author = {Schmidt, Katja and Walz, Ariane and Martin-Lopez, Berta and Sachse, Rene}, title = {Testing socio-cultural valuation methods of ecosystem services to explain land use preferences}, series = {Ecosystem Services : Science, Policy and Practice}, volume = {26}, journal = {Ecosystem Services : Science, Policy and Practice}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2212-0416}, doi = {10.1016/j.ecoser.2017.07.001}, pages = {270 -- 288}, year = {2017}, abstract = {Socio-cultural valuation still emerges as a methodological field in ecosystem service (ES) research and until now lacks consistent formalisation and balanced application in ES assessments. In this study, we examine the explanatory value of ES values for land use preferences. We use 563 responses to a survey about the Pentland Hills regional park in Scotland. Specifically, we aim to (1) identify clusters of land use preferences by using a novel visualisation tool, (2) test if socio-cultural values of ESs or (3) user characteristics are linked with land use preferences, and (4) determine whether both socio-cultural values of ESs and user characteristics can predict land use preferences. Our results suggest that there are five groups of people with different land use preferences, ranging from forest and nature enthusiasts to traditionalists, multi-functionalists and recreation seekers. Rating and weighting of ESs and user characteristics were associated with different clusters. Neither socio-cultural values nor user characteristics were suitable predictors for land use preferences. While several studies have explored land use preferences by identifying socio-cultural values in the past, our findings imply that in this case study ES values inform about general perceptions but do not replace the assessment of land use preferences. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.}, language = {en} } @misc{Zoeller2017, author = {Z{\"o}ller, Gert}, title = {Comment on "Estimation of Earthquake Hazard Parameters from Incomplete Data Files. Part III. Incorporation of Uncertainty of Earthquake-Occurrence Model" by Andrzej Kijko, Ansie Smit, and Markvard A. Sellevoll}, series = {Bulletin of the Seismological Society of America}, volume = {107}, journal = {Bulletin of the Seismological Society of America}, publisher = {Seismological Society of America}, address = {Albany}, issn = {0037-1106}, doi = {10.1785/0120160193}, pages = {1975 -- 1978}, year = {2017}, abstract = {Kijko et al. (2016) present various methods to estimate parameters that are relevant for probabilistic seismic-hazard assessment. One of these parameters, although not the most influential, is the maximum possible earthquake magnitude m(max). I show that the proposed estimation of m(max) is based on an erroneous equation related to a misuse of the estimator in Cooke (1979) and leads to unstable results. So far, reported finite estimations of m(max) arise from data selection, because the estimator in Kijko et al. (2016) diverges with finite probability. This finding is independent of the assumed distribution of earthquake magnitudes. For the specific choice of the doubly truncated Gutenberg-Richter distribution, I illustrate the problems by deriving explicit equations. Finally, I conclude that point estimators are generally not a suitable approach to constrain m(max).}, language = {en} } @article{MelnickCharletEchtleretal.2006, author = {Melnick, Daniel and Charlet, Francois and Echtler, Helmut P. and De Batist, Marc}, title = {Incipient axial collapse of the Main Cordillera and strain partitioning gradient between the central and Patagonian Andes, Lago Laja, Chile}, series = {Tectonics}, volume = {25}, journal = {Tectonics}, number = {5}, publisher = {Union}, address = {Washington}, issn = {0278-7407}, doi = {10.1029/2005TC001918}, pages = {22}, year = {2006}, abstract = {Lago Laja is a late Quaternary volcanic-dammed lake located near the drainage divide of the south central Andes. Field observations, lake reflection seismic profiles, bathymetry, and remote sensing data reveal an active fault system that runs parallel to the volcanic arc along the axis of the Main Cordillera, the Lago Laja fault system (LLFS). Normal faults of this extensional system cut late Pleistocene volcanics, <7.1 ka still water lacustrine sediments, 6.3 ka pyroclastic deposits, and Holocene alluvial fans. We divide the LLFS in three segments on the basis of fault geometry, width, and slip magnitude. The underwater faults of the central segment in the lake's deepest part have the maximum Holocene vertical slip rate of >2.7 mm/yr. Since 7.1 ka, the LLFS accounts for ∼0.7\% of arc-normal extension at an average minimum rate of 1.2 mm/yr and strain rate of ∼10-14 s-1. Seismites and surface ruptures evidence M>6 paleoearthquakes. The Main Cordillera at ∼37°S is a large-scale pop-up structure uplifted by thrusting along its foothills. In this light, we interpret extension in the axial and highest part of the Andes as incipient synorogenic gravitational collapse in response to uplift and crustal thickening. Thermal weakening due to elevated heat flow and postglacial lithospheric rebound and unbending have probably contributed to the arc-limited collapse and Holocene acceleration of deformation rates. The lack of significant strike-slip offsets along the LLFS as well as along both foothills-thrust systems at 37°S contrasts with the intra-arc dextral fault zone south of 38°S. Regional structural data indicates that north of 38°S, diffusely distributed strain reflects low partitioning of oblique subduction, while to the south deformation is localized in a discrete strike-slip fault zone along the volcanic arc, reflecting a higher degree of partitioning. We relate this strain partitioning gradient to favorable fault orientations in the fore arc north of the Arauco Peninsula, a major seismotectonic boundary.}, language = {en} } @article{MuellerLichtCampbelletal.2019, author = {Mueller, Megan A. and Licht, Alexis and Campbell, C. and Ocakoglu, F. and Taylor, Marc Hollis and Burch, L. and Ugrai, Tamas and Kaya, M. and Kurtoglu, B. and Coster, P. M. C. and Metais, Mustafa Y{\"u}cel and Beard, Kenneth Christopher}, title = {Collision Chronology Along the Izmir-Ankara-Erzincan Suture Zone: Insights From the Saricakaya Basin, Western Anatolia}, series = {Tectonics}, volume = {38}, journal = {Tectonics}, number = {10}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0278-7407}, doi = {10.1029/2019TC005683}, pages = {3652 -- 3674}, year = {2019}, abstract = {Debate persists concerning the timing and geodynamics of intercontinental collision, style of syncollisional deformation, and development of topography and fold-and-thrust belts along the >1,700-km-long Izmir-Ankara-Erzincan suture zone (IAESZ) in Turkey. Resolving this debate is a necessary precursor to evaluating the integrity of convergent margin models and kinematic, topographic, and biogeographic reconstructions of the Mediterranean domain. Geodynamic models argue either for a synchronous or diachronous collision during either the Late Cretaceous and/or Eocene, followed by Eocene slab breakoff and postcollisional magmatism. We investigate the collision chronology in western Anatolia as recorded in the sedimentary archives of the 90-km-long Saricakaya Basin perched at shallow structural levels along the IAESZ. Based on new zircon U-Pb geochronology and depositional environment and sedimentary provenance results, we demonstrate that the Saricakaya Basin is an Eocene sedimentary basin with sediment sourced from both the IAESZ and Sogut Thrust fault to the south and north, respectively, and formed primarily by flexural loading from north-south shortening along the syncollisional Sogut Thrust. Our results refine the timing of collision between the Anatolides and Pontide terranes in western Anatolia to Maastrichtian-Middle Paleocene and Early Eocene crustal shortening and basin formation. Furthermore, we demonstrate contemporaneous collision, deformation, and magmatism across the IAESZ, supporting synchronous collision models. We show that regional postcollisional magmatism can be explained by renewed underthrusting instead of slab breakoff. This new IAESZ chronology provides additional constraints for kinematic, geodynamic, and biogeographic reconstructions of the Mediterranean domain.}, language = {en} } @article{RungeGrosse2020, author = {Runge, Alexandra and Grosse, Guido}, title = {Mosaicking Landsat and Sentinel-2 Data to Enhance LandTrendr Time Series Analysis in Northern High Latitude Permafrost Regions}, series = {Remote Sensing}, volume = {12}, journal = {Remote Sensing}, number = {15}, publisher = {MDPI}, address = {Basel}, issn = {2072-4292}, doi = {10.3390/rs12152471}, pages = {23}, year = {2020}, abstract = {Permafrost is warming in the northern high latitudes, inducing highly dynamic thaw-related permafrost disturbances across the terrestrial Arctic. Monitoring and tracking of permafrost disturbances is important as they impact surrounding landscapes, ecosystems and infrastructure. Remote sensing provides the means to detect, map, and quantify these changes homogeneously across large regions and time scales. Existing Landsat-based algorithms assess different types of disturbances with similar spatiotemporal requirements. However, Landsat-based analyses are restricted in northern high latitudes due to the long repeat interval and frequent clouds, in particular at Arctic coastal sites. We therefore propose to combine Landsat and Sentinel-2 data for enhanced data coverage and present a combined annual mosaic workflow, expanding currently available algorithms, such as LandTrendr, to achieve more reliable time series analysis. We exemplary test the workflow for twelve sites across the northern high latitudes in Siberia. We assessed the number of images and cloud-free pixels, the spatial mosaic coverage and the mosaic quality with spectral comparisons. The number of available images increased steadily from 1999 to 2019 but especially from 2016 onward with the addition of Sentinel-2 images. Consequently, we have an increased number of cloud-free pixels even under challenging environmental conditions, which then serve as the input to the mosaicking process. In a comparison of annual mosaics, the Landsat+Sentinel-2 mosaics always fully covered the study areas (99.9-100 \%), while Landsat-only mosaics contained data-gaps in the same years, only reaching coverage percentages of 27.2 \%, 58.1 \%, and 69.7 \% for Sobo Sise, East Taymyr, and Kurungnakh in 2017, respectively. The spectral comparison of Landsat image, Sentinel-2 image, and Landsat+Sentinel-2 mosaic showed high correlation between the input images and mosaic bands (e.g., for Kurungnakh 0.91-0.97 between Landsat and Landsat+Sentinel-2 mosaic and 0.92-0.98 between Sentinel-2 and Landsat+Sentinel-2 mosaic) across all twelve study sites, testifying good quality mosaic results. Our results show that especially the results for northern, coastal areas was substantially improved with the Landsat+Sentinel-2 mosaics. By combining Landsat and Sentinel-2 data we accomplished to create reliably high spatial resolution input mosaics for time series analyses. Our approach allows to apply a high temporal continuous time series analysis to northern high latitude permafrost regions for the first time, overcoming substantial data gaps, and assess permafrost disturbance dynamics on an annual scale across large regions with algorithms such as LandTrendr by deriving the location, timing and progression of permafrost thaw disturbances}, language = {en} } @article{AichnerMakhmudovRajabovetal.2019, author = {Aichner, Bernhard and Makhmudov, Zafar and Rajabov, Iljomjon and Zhang, Qiong and Pausata, Francesco Salvatore R. and Werner, Martin and Heinecke, Liv and Kuessner, Marie L. and Feakins, Sarah J. and Sachse, Dirk and Mischke, Steffen}, title = {Hydroclimate in the Pamirs Was Driven by Changes in Precipitation-Evaporation Seasonality Since theLast Glacial Period}, series = {Geophysical research letters}, volume = {46}, journal = {Geophysical research letters}, number = {23}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2019GL085202}, pages = {13972 -- 13983}, year = {2019}, abstract = {The Central Asian Pamir Mountains (Pamirs) are a high-altitude region sensitive to climatic change, with only few paleoclimatic records available. To examine the glacial-interglacial hydrological changes in the region, we analyzed the geochemical parameters of a 31-kyr record from Lake Karakul and performed a set of experiments with climate models to interpret the results. delta D values of terrestrial biomarkers showed insolation-driven trends reflecting major shifts of water vapor sources. For aquatic biomarkers, positive delta D shifts driven by changes in precipitation seasonality were observed at ca. 31-30, 28-26, and 17-14 kyr BP. Multiproxy paleoecological data and modelling results suggest that increased water availability, induced by decreased summer evaporation, triggered higher lake levels during those episodes, possibly synchronous to northern hemispheric rapid climate events. We conclude that seasonal changes in precipitation-evaporation balance significantly influenced the hydrological state of a large waterbody such as Lake Karakul, while annual precipitation amount and inflows remained fairly constant.}, language = {en} } @article{MarkowskaFohlmeisterTrebleetal.2019, author = {Markowska, Monika and Fohlmeister, Jens Bernd and Treble, Pauline C. and Baker, Andy and Andersen, Martin S. and Hua, Quan}, title = {Modelling the C-14 bomb-pulse in young speleothems using a soil carbon continuum model}, series = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society}, volume = {261}, journal = {Geochimica et cosmochimica acta : journal of the Geochemical Society and the Meteoritical Society}, publisher = {Elsevier}, address = {Oxford}, issn = {0016-7037}, doi = {10.1016/j.gca.2019.04.029}, pages = {342 -- 367}, year = {2019}, abstract = {The 'bomb-pulse' method is a chronological approach to further constrain the age of speleothems that grew between 1950 CE - present. Establishing dependable chronological constraints is crucial for modern calibration studies of speleothems to instrumental climate records, which provides the basis for paleoclimate interpretations. However, a large unknown is how 14C is transferred from the atmosphere to any individual speleothem owing to the site-specific residence times of organic matter above cave systems. Here, we employ the bomb-pulse method to build chronologies from 14C measurements in combination with a new unsaturated zone C model which considers C decomposition as a continuum, to better understand unsaturated zone 14C dynamics. The bomb-pulse curves of eight speleothems from southern Australia in three contrasting climatic regions; the semi-arid Wellington Caves site, the mediterranean Golgotha Cave site and the montane Yarrangobilly Caves site, are investigated. Overall, the modelled 14C bomb-pulse curves produce excellent fits with measured 14C speleothem data (r2 = 0.82-0.99). The C modelling reveals that unsaturated zone C is predominately young at the semi-arid site, with a weighted-mean residence time of 32 years and that tree root respiration is likely an important source of vadose CO2. At the montane site, ∼39\% of C is young (<1 years), but the weighted-mean C ages are older (145-220 years). The mediterranean site has very little contribution from young C (<12\%: 0-1 years), with weighted-mean ages between 157 and 245 years, likely due to greater adsorption of organic matter in the upper vadose zone during matrix flow, and remobilisation of C from young syngenetic karst. New end members for low speleothem Dead Carbon Proportion (DCP) are identified (2.19\% and 1.65\%, respectively) for Australian montane and semi-arid zone speleothems, where oversupply of modern CO2 in the vadose zone leads to lower DCP. It is also demonstrated that DCP can be quite variable over small time scales, that processes may be difficult to untangle and a constant DCP assumption is likely invalid. DCP variability over time is mainly controlled by the changes vadose zone CO2, where vegetation regeneration, wild-fires and karst hydrology play an important role.}, language = {en} } @article{SaltikoffFriedrichSoderholmetal.2019, author = {Saltikoff, Elena and Friedrich, Katja and Soderholm, Joshua and Lengfeld, Katharina and Nelson, Brian and Becker, Andreas and Hollmann, Rainer and Urban, Bernard and Heistermann, Maik and Tassone, Caterina}, title = {An Overview of Using Weather Radar for Climatological Studies: Successes, Challenges, and Potential}, series = {Bulletin of the American Meteorological Society}, volume = {100}, journal = {Bulletin of the American Meteorological Society}, number = {9}, publisher = {American Meteorological Soc.}, address = {Boston}, issn = {0003-0007}, doi = {10.1175/BAMS-D-18-0166.1}, pages = {1739 -- 1751}, year = {2019}, abstract = {Weather radars have been widely used to detect and quantify precipitation and nowcast severe weather for more than 50 years. Operational weather radars generate huge three-dimensional datasets that can accumulate to terabytes per day. So it is essential to review what can be done with existing vast amounts of data, and how we should manage the present datasets for the future climatologists. All weather radars provide the reflectivity factor, and this is the main parameter to be archived. Saving reflectivity as volumetric data in the original spherical coordinates allows for studies of the three-dimensional structure of precipitation, which can be applied to understand a number of processes, for example, analyzing hail or thunderstorm modes. Doppler velocity and polarimetric moments also have numerous applications for climate studies, for example, quality improvement of reflectivity and rain rate retrievals, and for interrogating microphysical and dynamical processes. However, observational data alone are not useful if they are not accompanied by sufficient metadata. Since the lifetime of a radar ranges between 10 and 20 years, instruments are typically replaced or upgraded during climatologically relevant time periods. As a result, present metadata often do not apply to past data. This paper outlines the work of the Radar Task Team set by the Atmospheric Observation Panel for Climate (AOPC) and summarizes results from a recent survey on the existence and availability of long time series. We also provide recommendations for archiving current and future data and examples of climatological studies in which radar data have already been used.}, language = {en} } @article{HudsonBotzenAerts2019, author = {Hudson, Paul and Botzen, W. J. Wouter and Aerts, Jeroen C. J. H.}, title = {Flood insurance arrangements in the European Union for future flood risk under climate and socioeconomic change}, series = {Global environmental change : human and policy dimensions}, volume = {58}, journal = {Global environmental change : human and policy dimensions}, publisher = {Elsevier}, address = {Oxford}, issn = {0959-3780}, doi = {10.1016/j.gloenvcha.2019.101966}, pages = {13}, year = {2019}, abstract = {Flood risk will increase in many areas around the world due to climate change and increase in economic exposure. This implies that adequate flood insurance schemes are needed to adapt to increasing flood risk and to minimise welfare losses for households in flood-prone areas. Flood insurance markets may need reform to offer sufficient and affordable financial protection and incentives for risk reduction. Here, we present the results of a study that aims to evaluate the ability of flood insurance arrangements in Europe to cope with trends in flood risk, using criteria that encompass common elements of the policy debate on flood insurance reform. We show that the average risk-based flood insurance premium could double between 2015 and 2055 in the absence of more risk reduction by households exposed to flooding. We show that part of the expected future increase in flood risk could be limited by flood insurance mechanisms that better incentivise risk reduction by policyholders, which lowers vulnerability. The affordability of flood insurance can be improved by introducing the key features of public-private partnerships (PPPs), which include public reinsurance, limited premium cross-subsidisation between low- and high-risk households, and incentives for policyholder-level risk reduction. These findings were evaluated in a comprehensive sensitivity analysis and support ongoing reforms in Europe and abroad that move towards risk-based premiums and link insurance with risk reduction, strengthen purchase requirements, and engage in multi-stakeholder partnerships.}, language = {en} } @article{KornherKalkuhl2019, author = {Kornher, Lukas and Kalkuhl, Matthias}, title = {The gains of coordination - When does regional cooperation for food security make sense?}, series = {Global Food Security - AGRICULTURE POLICY ECONOMICS AND ENVIRONMENT}, volume = {22}, journal = {Global Food Security - AGRICULTURE POLICY ECONOMICS AND ENVIRONMENT}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2211-9124}, doi = {10.1016/j.gfs.2019.09.004}, pages = {37 -- 45}, year = {2019}, abstract = {With the onset of the global food crisis, the discussion about the use and misuse of agricultural market interventions regained academic attention. As a result of economies of scale, centralized policy implementation at the regional level has the potential to reduce the budgetary costs of policies. Borrowing from the literature on international unions and international policy coordination, we develop a conceptual framework to analyze when regional policy implementation makes sense. This is the case whenever spill-overs from centralization are large and policy preferences, driven by country-specific characteristics, are homogeneous. Subsequently, we examine the advantageousness of centralized policy implementation for the West African region regarding the most common food security policies. We show that centralization of trade policies and emergency food reserves is beneficial, while buffer stocks, safety net policies, and producer support policies should be implemented at the national level.}, language = {en} } @article{HuaCookFohlmeisteretal.2017, author = {Hua, Quan and Cook, Duncan and Fohlmeister, Jens Bernd and Penny, Dan and Bishop, Paul and Buckman, Solomon}, title = {Radiocarbon Dating of a Speleothem Record of Paleoclimate for Angkor, Cambodia}, series = {Radiocarbon : an international journal of cosmogenic isotope research}, volume = {59}, journal = {Radiocarbon : an international journal of cosmogenic isotope research}, number = {Special Issue 6 / 2}, publisher = {The University of Arizona, Department of Geosciences}, address = {Tucson, Ariz.}, issn = {0033-8222}, doi = {10.1017/RDC.2017.115}, pages = {1873 -- 1890}, year = {2017}, abstract = {We report the chronological construction for the top portion of a speleothem, PC1, from southern Cambodia with the aim of reconstructing a continuous high-resolution climate record covering the fluorescence and decline of the medieval Khmer kingdom and its capital at Angkor (similar to 9th-15th centuries AD). Earlier attempts to date PC1 by the standard U-Th method proved unsuccessful. We have therefore dated this speleothem using radiocarbon. Fifty carbonate samples along the growth axis of PC1 were collected for accelerator mass spectrometry (AMS) analysis. Chronological reconstruction for PC1 was achieved using two different approaches described by Hua et al. (2012a) and Lechleitner et al. (2016a). Excellent concordance between the two age-depth models indicates that the top similar to 47 mm of PC1 grew during the last millennium with a growth hiatus during similar to 1250-1650 AD, resulting from a large change in measured C-14 values at 34.4-35.2 mm depth. The timing of the growth hiatus covers the period of decades-long droughts during the 14th-16th centuries AD indicated in regional climate records.}, language = {en} } @article{MargirierBraunGautheronetal.2019, author = {Margirier, Audrey and Braun, Jean and Gautheron, Cecile and Carcaillet, Julien and Schwartz, Stephane and Jamme, Rosella Pinna and Stanley, Jessica}, title = {Climate control on Early Cenozoic denudation of the Namibian margin as deduced from new thermochronological constraints}, series = {Earth \& planetary science letters}, volume = {527}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2019.115779}, pages = {11}, year = {2019}, abstract = {The processes that control long term landscape evolution in continental interiors and, in particular, along passive margins such as in southern Africa, are still the subject of much debate (e.g. Braun, 2018). Although today the Namibian margin is characterized by an arid climate, it has experienced climatic fluctuations during the Cenozoic and, yet, to date no study has documented the potential role of climate on its erosion history. In western Namibia, the Brandberg Massif, an erosional remnant or inselberg, provides a good opportunity to document the Cenozoic denudation history of the margin using the relationship between rock cooling or exhumation ages and their elevation. Here we provide new apatite (UThSm)/He dates on the Brandberg Inselberg that range from 151 +/- 12 to 30 +/- 2 Ma. Combined with existing apatite fission track data, they yield new constraints on the denudation history of the margin. These data document two main cooling phases since continental break-up 130 Myr ago, a rapid one (similar to 10 degrees C/Myr) following break-up and a slower one (similar to 12 degrees C/Myr) between 65 and 35 Ma. We interpret them respectively to be related to escarpment erosion following rifting and continental break-up and as a phase of enhanced denudation during the Early Eocene Climatic Optimum. We propose that during the Early Eocene Climatic Optimum chemical weathering was important and contributed significantly to the denudation of the Namibian margin and the formation of a pediplain around the Brandberg and enhanced valley incision within the massif. Additionally, aridification of the region since 35 Ma has resulted in negligible denudation rates since that time. (C) 2019 Elsevier B.V. All rights reserved.}, language = {en} } @article{PenaHeidbachMorenoetal.2019, author = {Pena, Carlos and Heidbach, Oliver and Moreno, Marcos and Bedford, Jonathan and Ziegler, Moritz 0. and Tassara, Andres Ollero and Oncken, Onno}, title = {Role of Lower Crust in the Postseismic Deformation of the 2010 Maule Earthquake: Insights from a Model with Power-Law Rheology}, series = {Pure and applied geophysics}, volume = {176}, journal = {Pure and applied geophysics}, number = {9}, publisher = {Springer}, address = {Basel}, issn = {0033-4553}, doi = {10.1007/s00024-018-02090-3}, pages = {3913 -- 3928}, year = {2019}, abstract = {The surface deformation associated with the 2010 M-w 8.8 Maule earthquake in Chile was recorded in great detail before, during and after the event. The high data quality of the continuous GPS (cGPS) observations has facilitated a number of studies that model the postseismic deformation signal with a combination of relocking, afterslip and viscoelastic relaxation using linear rheology for the upper mantle. Here, we investigate the impact of using linear Maxwell or power-law rheology with a 2D geomechanical-numerical model to better understand the relative importance of the different processes that control the postseismic deformation signal. Our model results reveal that, in particular, the modeled cumulative vertical postseismic deformation pattern in the near field (< 300 km from the trench) is very sensitive to the location of maximum afterslip and choice of rheology. In the model with power-law rheology, the afterslip maximum is located at 20-35 km rather than > 50 km depth as suggested in previous studies. The explanation for this difference is that in the model with power-law rheology the relaxation of coseismically imposed differential stresses occurs mainly in the lower crust. However, even though the model with power-law rheology probably has more potential to explain the vertical postseismic signal in the near field, the uncertainty of the applied temperature field is substantial, and this needs further investigations and improvements.}, language = {en} } @article{FosterLehrmannYuetal.2019, author = {Foster, William J. and Lehrmann, Daniel J. and Yu, Meiyi and Martindale, Rowan C.}, title = {Facies selectivity of benthic invertebrates in a Permian/Triassic boundary microbialite succession: Implications for the "microbialite refuge" hypothesis}, series = {Geobiology}, volume = {17}, journal = {Geobiology}, number = {5}, publisher = {Wiley}, address = {Hoboken}, issn = {1472-4677}, doi = {10.1111/gbi.12343}, pages = {523 -- 535}, year = {2019}, abstract = {Thrombolite and stromatolite habitats are becoming increasingly recognized as important refuges for invertebrates during Phanerozoic Oceanic Anoxic Events (OAEs); it is posited that oxygenic photosynthesis by cyanobacteria in these microbialites provided a refuge from anoxic conditions (i.e., the "microbialite refuge" hypothesis). Here, we test this hypothesis by investigating the distribution of ~34, 500 benthic invertebrate fossils found in ~100 samples from a microbialite succession that developed following the latest Permian mass extinction event on the Great Bank of Guizhou (South China), representing microbial (stromatolites and thrombolites) and non-microbial facies. The stromatolites were the least taxonomically diverse facies, and the thrombolites also recorded significantly lower diversities when compared to the non-microbial facies. Based on the distribution and ornamentation of the bioclasts within the thrombolites and stromatolites, the bioclasts are inferred to have been transported and concentrated in the non-microbial fabrics, that is, cavities around the microbial framework. Therefore, many of the identified metazoans from the post-extinction microbialites are not observed to have been living within a microbial mat. Furthermore, the lifestyle of many of the taxa identified from the microbialites was not suited for, or even amenable to, life within a benthic microbial mat. The high diversity of oxygen-dependent metazoans in the non-microbial facies on the Great Bank of Guizhou, and inferences from geochemical records, suggests that the microbialites and benthic communities developed in oxygenated environments, which disproves that the microbes were the source of the oxygenation. Instead, we posit that microbialite successions represent a taphonomic window for exceptional preservation of the biota, similar to a Konzentrat-Lagerstatte, which has allowed for diverse fossil assemblages to be preserved during intervals of poor preservation.}, language = {en} } @article{WenzlaffWinterleitnerSchutz2019, author = {Wenzlaff, Christian and Winterleitner, Gerd and Schutz, Felina}, title = {Controlling parameters of a mono-well high-temperature aquifer thermal energy storage in porous media, northern Oman}, series = {Petroleum geoscience}, volume = {25}, journal = {Petroleum geoscience}, number = {3}, publisher = {Geological Soc. Publ. House}, address = {Bath}, issn = {1354-0793}, doi = {10.1144/petgeo2018-104}, pages = {337 -- 349}, year = {2019}, abstract = {Aquifer thermal energy storage (ATES) as a complement to fluctuating renewable energy systems is a reliable technology to guarantee continuous energy supply for heating and air conditioning. We investigated a high-temperature (HT) mono-well system (c. 100 degrees C), where the well screens are separated vertically within the aquifer, as an alternative to conventional doublet ATES systems for an underground storage in northern Oman. We analysed the impact of thermal inference between injection and extraction well screens on the heat recovery factor (HRF) in order to define the optimal screento-screen distance for best possible systems efficiency. Two controlling interference parameters were considered: the vertical screen-to-screen distance and aquifer heterogeneities. The sensitivity study shows that with decreasing screen-to-screen distances, thermal interference increases storage performance. A turning point is reached if the screen distance is too close, causing either water breakthrough or negative thermal interference between the screens. Our simulations show that a combined heat plume with spherical geometry results in the highest heat recovery factors due to the lowest surface area to volume ratios. Thick aquifers for mono-well HT-ATES are thus not mandatory Our study shows that a HT-ATES mono-well system is a feasible storage design with high heat recovery factors for continuous cooling or heating purposes.}, language = {en} } @article{CerantolaWilkeKantoretal.2019, author = {Cerantola, Valerio and Wilke, Max and Kantor, Innokenty and Ismailova, Leyla and Kupenko, Ilya and McCammon, Catherine and Pascarelli, Sakura and Dubrovinsky, Leonid S.}, title = {Experimental investigation of FeCO3 (siderite) stability in Earth's lower mantle using XANES spectroscopy}, series = {American mineralogist : an international journal of earth and planetary materials}, volume = {104}, journal = {American mineralogist : an international journal of earth and planetary materials}, number = {8}, publisher = {Mineralogical Society of America}, address = {Chantilly}, issn = {0003-004X}, doi = {10.2138/am-2019-6428}, pages = {1083 -- 1091}, year = {2019}, abstract = {We studied FeCO3 using Fe K-edge X-ray absorption near-edge structure (XANES) spectroscopy at pressures up to 54 GPa and temperatures above 2000 K. First-principles calculations of Fe at the K-edge in FeCO3 were performed to support the interpretation of the XANES spectra. The variation of iron absorption edge features with pressure and temperature in FeCO3 matches well with recently reported observations on FeCO3 at extreme conditions, and provides new insight into the stability of Fe-carbonates in Earth's mantle. Here we show that at conditions of the mid-lower mantle, ~50 GPa and ~2200 K, FeCO3 melts and partially decomposes to high-pressure Fe3O4. Carbon (diamond) and oxygen are also inferred products of the reaction. We constrained the thermodynamic phase boundary between crystalline FeCO3 and melt to be at 51(1) GPa and ~1850 K. We observe that at 54(1) GPa, temperature-induced spin crossover of Fe2+ takes place from low to high spin such that at 1735(100) K, all iron in FeCO3 is in the high-spin state. A comparison between experiment and theory provides a more detailed understanding of FeCO3 decomposition observed in X-ray absorption spectra and helps to explain spectral changes due to pressure-induced spin crossover in FeCO3 at ambient temperature.}, language = {en} } @article{BernardezPregoVirginiaFilgueirasetal.2017, author = {Bernardez, Patricia and Prego, Ricardo and Virginia Filgueiras, Ana and Ospina-Alvarez, Natalia and Santos-Echeandia, Juan and Angel Alvarez-Vazquez, Miguel and Caetano, Miguel}, title = {Lithogenic sources, composition and intra-annual variability of suspended particulate matter supplied from rivers to the Northern Galician Rias (Bay of Biscay)}, series = {Journal of sea research}, volume = {130}, journal = {Journal of sea research}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1385-1101}, doi = {10.1016/j.seares.2017.05.006}, pages = {73 -- 84}, year = {2017}, abstract = {Scarce research about small European rivers from non-human impacted areas to determine their natural background state has been undertaken. During the annual hydrological cycle of 2008-9 the patterns of particulate supply (SPM, POC, PON, Al, Cd, Co, Cr, Cu, Fe, Ni, Pb, V, Zn) from the rivers Sor, Mera Landro, Lourido and Landoi to the Northern Galician Rias (SW Bay of Biscay) were tackled. No differences in the composition of the SPM were detected for the studied rivers regarding Al, Fe and POC but the relative percentage of particulate trace elements (PTE) discriminate the rivers. So, Cr, Co and Ni in the Lourido, and Landoi rivers, and Cu in the Mera River, are controlled by watershed minerals of Ortegal Geological Complex while for the rest rivers PTE are by granitic and Ollo de Sapo bedrock watershed. Therefore, the imprint of PTE in the parental rocks of the river basins is reflected on the coastal sediments of the Rias. The main process controlling the dynamics and variations of chemical elements in the particulate form is the river discharge. This fact exemplifies that these rivers presents a natural behavior not being highly influenced by anthropogenic activities.}, language = {en} } @article{WeisshuhnRecklingStachowetal.2017, author = {Weisshuhn, Peter and Reckling, Moritz and Stachow, Ulrich and Wiggering, Hubert}, title = {Supporting Agricultural Ecosystem Services through the Integration of Perennial Polycultures into Crop Rotations}, series = {Sustainability}, volume = {9}, journal = {Sustainability}, publisher = {MDPI}, address = {Basel}, issn = {2071-1050}, doi = {10.3390/su9122267}, pages = {20}, year = {2017}, abstract = {This review analyzes the potential role and long-term effects of field perennial polycultures (mixtures) in agricultural systems, with the aim of reducing the trade-offs between provisioning and regulating ecosystem services. First, crop rotations are identified as a suitable tool for the assessment of the long-term effects of perennial polycultures on ecosystem services, which are not visible at the single-crop level. Second, the ability of perennial polycultures to support ecosystem services when used in crop rotations is quantified through eight agricultural ecosystem services. Legume-grass mixtures and wildflower mixtures are used as examples of perennial polycultures, and compared with silage maize as a typical crop for biomass production. Perennial polycultures enhance soil fertility, soil protection, climate regulation, pollination, pest and weed control, and landscape aesthetics compared with maize. They also score lower for biomass production compared with maize, which confirms the trade-off between provisioning and regulating ecosystem services. However, the additional positive factors provided by perennial polycultures, such as reduced costs for mineral fertilizer, pesticides, and soil tillage, and a significant preceding crop effect that increases the yields of subsequent crops, should be taken into account. However, a full assessment of agricultural ecosystem services requires a more holistic analysis that is beyond the capabilities of current frameworks.}, language = {en} } @article{HainzlZoellerMain2006, author = {Hainzl, Sebastian and Z{\"o}ller, Gert and Main, Ian}, title = {Introduction to special issue: Dynamics of seismicity patterns and earthquake triggering - Preface}, series = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, volume = {424}, journal = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, number = {Special issue}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0040-1951}, doi = {10.1016/j.tecto.2006.03.034}, pages = {135 -- 138}, year = {2006}, language = {en} } @phdthesis{Schimpf2020, author = {Schimpf, Stefan}, title = {Herkunft und Ablagerungsmilieu quart{\"a}rer Sedimente im Einzugsgebiet des Heihe, NW China}, school = {Universit{\"a}t Potsdam}, pages = {xi, 186}, year = {2020}, abstract = {Der zentralasiatische Naturraum, wie er sich uns heute pr{\"a}sentiert, ist das Ergebnis eines Zusammenwirkens vieler verschiedener Faktoren {\"u}ber Jahrmillionen hinweg. Im aktuellen Kontext des Klimawandels zeigt sich jedoch, wie stark sich Stofffl{\"u}sse auch kurzfristig {\"a}ndern und dabei das Gesicht der Landschaft verwandeln k{\"o}nnen. Die Gobi-W{\"u}ste in der Inneren Mongolei (China), als Teil der gleichnamigen Trockenregionen Nordwestchinas, ist aufgrund der Ausgestaltung ihrer landschaftspr{\"a}genden Elemente sowie ihrer Landschaftsdynamik, im Zusammenhang mit der Lage zum Tibet-Plateau, in den Fokus der klimageschichtlichen Grundlagenforschung ger{\"u}ckt. Als großes Langzeitarchiv unterschiedlichster fluvialer, lakustriner und {\"a}olischer Sedimente stellt sie eine bedeutende Lokalit{\"a}t zur Rekonstruktion von lokalen und regionalen Stofffl{\"u}ssen dar.. Andererseits ist die Gobi-W{\"u}ste zugleich auch eine bedeutende Quelle f{\"u}r den {\"u}berregionalen Staubtransport, da sie aufgrund der klimatischen Bedingungen insbesondere der Erosion durch Ausblasung preisgegeben wird. Vor diesem Hintergrund erfolgten zwischen 2011 und 2014, im Rahmen des BMBF-Verbundprogramms WTZ Zentralasien - Monsundynamik \& Geo{\"o}kosysteme (F{\"o}rderkennzeichen 03G0814), mehrere deutsch-chinesische Expeditionen in das Ejina-Becken (Innere Mongolei) und das Qilian Shan-Vorland. Im Zuge dieser Expeditionen wurden f{\"u}r eine Bestimmung potenzieller Sedimentquellen erstmals zahlreiche Oberfl{\"a}chenproben aus dem gesamten Einzugsgebiet des Heihe (schwarzer Fluss) gesammelt. Zudem wurden mit zwei Bohrungen im inneren des Ejina-Beckens, erg{\"a}nzende Sedimentbohrkerne zum bestehenden Bohrkern D100 (siehe W{\"u}nnemann (2005)) abgeteuft, um weit reichende, erg{\"a}nzende Informationen zur Landschaftsgeschichte und zum {\"u}berregionalen Sedimenttransfer zu erhalten. Gegenstand und Ziel der vorliegenden Doktorarbeit ist die sedimentologisch-mineralogische Charakterisierung des Untersuchungsgebietes in Bezug auf potenzielle Sedimentquellen und Stofffl{\"u}sse des Ejina-Beckens sowie die Rekonstruktion der Ablagerungsgeschichte eines dort erbohrten, 19m langen Sedimentbohrkerns (GN100). Schwerpunkt ist hierbei die Kl{\"a}rung der Sedimentherkunft innerhalb des Bohrkerns sowie die Ausweisung von Herkunftssignalen und m{\"o}glichen Sedimentquellen bzw. Sedimenttransportpfaden. Die methodische Herangehensweise basiert auf einem Multi-Proxy-Ansatz zur Charakterisierung der klastischen Sedimentfazies anhand von Gel{\"a}ndebeobachtungen, lithologisch-granulometrischen und mineralogisch-geochemischen Analysen sowie statistischen Verfahren. F{\"u}r die mineralogischen Untersuchungen der Sedimente wurde eine neue, rasterelektronenmikroskopische Methode zur automatisierten Partikelanalyse genutzt und den traditionellen Methoden gegen{\"u}bergestellt. Die synoptische Betrachtung der granulometrischen, geochemischen und mineralogischen Befunde der Oberfl{\"a}chensedimente ergibt f{\"u}r das Untersuchungsgebiet ein logisches Kaskadenmodell mit immer wiederkehrenden Prozessbereichen und {\"a}hnlichen Prozesssignalen. Die umfangreichen granulometrischen Analysen deuten dabei auf abnehmende Korngr{\"o}ßen mit zunehmender Entfernung vom Qilian Shan hin und erm{\"o}glichen die Identifizierung von vier texturellen Signalen: den fluvialen Sanden, den D{\"u}nensanden, den Stillwassersedimenten und St{\"a}uben. Diese Ergebnisse k{\"o}nnen als Interpretationsgrundlage f{\"u}r die Korngr{\"o}ßenanalysen des Bohrkerns genutzt werden. Somit ist es m{\"o}glich, die Ablagerungsgeschichte der Bohrkernsedimente zu rekonstruieren und in Verbindung mit eigenen und literaturbasierten Datierungen in einen Gesamtkontext einzuh{\"a}ngen. F{\"u}r das Untersuchungsgebiet werden somit vier Ablagerungsphasen ausgewiesen, die bis in die Zeit des letzten glazialen Maximums (LGM) zur{\"u}ckreichen. W{\"a}hrend dieser Ablagerungsphasen kam es im Zuge unterschiedlicher Aktivit{\"a}ts- und Stabilit{\"a}tsphasen zu einer kontinuierlichen Progradation und {\"U}berpr{\"a}gung des Schwemmf{\"a}chers. Eine besonders aktive Phase kann zwischen 8 ka und 4 ka BP festgestellt werden, w{\"a}hrend der es aufgrund zunehmender fluvialer Aktivit{\"a}ten zu einer deutlich verst{\"a}rkten Schwemmf{\"a}cherdynamik gekommen zu sein scheint. In den Abschnitten davor und danach waren es vor allem {\"a}olische Prozesse, die zu einer {\"U}berpr{\"a}gung des Schwemmf{\"a}chers gef{\"u}hrt haben. Hinsichtlich der mineralogischen Herkunftssignale gibt es eine große Variabilit{\"a}t. Dies spiegelt die enorme Heterogenit{\"a}t der Geologie des Untersuchungsgebietes wider, wodurch die r{\"a}umlichen Signale nicht sehr stark ausgepr{\"a}gt sind. Dennoch, k{\"o}nnen f{\"u}r das Einzugsgebiet drei gr{\"o}ßere Bereiche deklariert werden, die als Herkunftsgebiet in Frage kommen. Das {\"o}stliche Qilian Shan Vorland zeichnet sich dabei durch deutlich h{\"o}here Chloritgehalte als prim{\"a}re Quelle f{\"u}r die Sedimente im Ejina-Becken aus. Sie unterscheiden sich insbesondere durch stark divergierende Chloritgehalte in der Tonmineral- und Gesamtmineralfraktion, was das {\"o}stliche Qilian Shan Vorland als prim{\"a}re Quelle f{\"u}r die Sedimente im Ejina-Becken auszeichnet. Dies steht in Zusammenhang mit den Gr{\"u}nschiefern, Ophioliten und Serpentiniten in diesem Bereich. Geochemisch deutet vor allem das Cr/Rb-Verh{\"a}ltnis eine große Variabilit{\"a}t innerhalb des Einzugsgebietes an. Auch hier ist es das {\"o}stliche Vorland, welches aufgrund seines hohen Anteils an mafischen Gesteinen reich an Chromiten und Spinellen ist und sich somit vom restlichen Untersuchungsgebiet abhebt. Die zeitliche aber auch die generelle Variabilit{\"a}t der Sedimentherkunft l{\"a}sst sich in den Bohrkernsedimenten nicht so deutlich nachzeichnen. Die mineralogisch-sedimentologischen Eigenschaften der erbohrten klastischen Sedimente zeugen zwar von zwischenzeitlichen {\"A}nderungen bei der Sedimentherkunft, diese sind jedoch nicht so deutlich ausgepr{\"a}gt, wie es die Quellsignale in den Oberfl{\"a}chensedimenten vermuten lassen. Ein Grund daf{\"u}r scheint die starke Vermischung unterschiedlichster Sedimente w{\"a}hrend des Transportes zu sein. Die Kombination der Korngr{\"o}ßenergebnisse mit den Befunden der Gesamt- und Schwermineralogie deuten darauf hin, dass es zwischenzeitlich eine Phase mit {\"u}berwiegend {\"a}olischen Prozessen gegeben hat, die mit einem Sedimenteintrag aus dem westlichen Bei Shan in Verbindung stehen. Neben der Zunahme ultrastabiler Schwerminerale wie Zirkon und Granat und der Abnahme opaker Schwerminerale, weisen vor allem die heutigen Verh{\"a}ltnisse darauf hin. Der Vergleich der traditionellen Schwermineralanalyse mit der Computer-Controlled-Scanning-Electron-Microscopy (kurz: CCSEM), die eine automatisierte Partikelauswertung der Proben erm{\"o}glicht, zeigt den deutlichen Vorteil der modernen Analysemethode. Neben einem zeitlichen Vorteil, den man durch die automatisierte Abarbeitung der vorbereiteten Proben erlangen kann, steht vor allem die deutlich gr{\"o}ßere statistische Signifikanz des Ergebnisses im Vordergrund. Zudem k{\"o}nnen mit dieser Methode auch chemische Variet{\"a}ten einiger Schwerminerale bestimmt werden, die eine noch feinere Klassifizierung und sicherere Aussagen zu einer m{\"o}glichen Sedimentherkunft erm{\"o}glichen. Damit ergeben sich außerdem verbesserte Aussagen zu Zusammensetzungen und Entstehungsprozessen der abgelagerten Sedimente. Die Studie verdeutlicht, dass die Sedimentherkunft innerhalb des Untersuchungsgebietes sowie die ablaufenden Prozesse zum Teil stark von lokalen Gegebenheiten abh{\"a}ngen. Die Heterogenit{\"a}t der Geologie und die Gr{\"o}ße des Einzugsgebietes sowie die daraus resultierende Komplexit{\"a}t der Sedimentgenese, machen exakte Zuordnungen zu klar definierten Sedimentquellen sehr schwer. Dennoch zeigen die Ergebnisse, dass die Sedimentzufuhr in das Ejina-Becken in erster Linie durch fluviale klastische Sedimente des Heihe aus dem Qilian Shan erfolgt sein muss. Die Untersuchungsergebnisse zeigen jedoch ebenso die Notwendigkeit einer erg{\"a}nzenden Bearbeitung angrenzender Untersuchungsgebiete, wie beispielsweise den Gobi-Altai im Norden oder den Beishan im Westen, sowie die Verdichtung der Oberfl{\"a}chenbeprobung zur feineren Aufl{\"o}sung von lokalen Sedimentquellen.}, language = {de} } @article{PanetChambodutDiamentetal.2006, author = {Panet, I. and Chambodut, Aude and Diament, M. and Holschneider, Matthias and Jamet, O.}, title = {New insights on intraplate volcanism in French Polynesia from wavelet analysis of GRACE, CHAMP, and sea surface data}, series = {Journal of geophysical research : Solid earth}, volume = {111}, journal = {Journal of geophysical research : Solid earth}, publisher = {Union}, address = {Washington}, issn = {0148-0227}, doi = {10.1029/2005JB004141}, pages = {17}, year = {2006}, abstract = {[ 1] In this paper, we discuss the origin of superswell volcanism on the basis of representation and analysis of recent gravity and magnetic satellite data with wavelets in spherical geometry. We computed a refined gravity field in the south central Pacific based on the GRACE satellite GGM02S global gravity field and the KMS02 altimetric grid, and a magnetic anomaly field based on CHAMP data. The magnetic anomalies are marked by the magnetic lineation of the seafloor spreading and by a strong anomaly in the Tuamotu region, which we interpret as evidence for crustal thickening. We interpret our gravity field through a continuous wavelet analysis that allows to get a first idea of the internal density distribution. We also compute the continuous wavelet analysis of the bathymetric contribution to discriminate between deep and superficial sources. According to the gravity signature of the different chains as revealed by our analysis, various processes are at the origin of the volcanism in French Polynesia. As evidence, we show a large-scale anomaly over the Society Islands that we interpret as the gravity signature of a deeply anchored mantle plume. The gravity signature of the Cook-Austral chain indicates a complex origin which may involve deep processes. Finally, we discuss the particular location of the Marquesas chain as suggesting that the origin of the volcanism may interfere with secondary convection rolls or may be controlled by lithospheric weakness due to the regional stress field, or else related to the presence of the nearby Tuamotu plateau.}, language = {en} } @article{DialloKuleshHolschneideretal.2006, author = {Diallo, Mamadou Sanou and Kulesh, Michail and Holschneider, Matthias and Kurennaya, Kristina and Scherbaum, Frank}, title = {Instantaneous polarization attributes based on an adaptive approximate covariance method}, series = {Geophysics}, volume = {71}, journal = {Geophysics}, number = {5}, publisher = {SEG}, address = {Tulsa}, issn = {0016-8033}, doi = {10.1190/1.2227522}, pages = {V99 -- V104}, year = {2006}, abstract = {We introduce a method for computing instantaneous-polarization attributes from multicomponent signals. This is an improvement on the standard covariance method (SCM) because it does not depend on the window size used to compute the standard covariance matrix. We overcome the window-size problem by deriving an approximate analytical formula for the cross-energy matrix in which we automatically and adaptively determine the time window. The proposed method uses polarization analysis as applied to multicomponent seismic by waveform separation and filtering.}, language = {en} } @misc{WongMasonBruneetal.2019, author = {Wong, Kevin and Mason, Emily and Brune, Sascha and East, Madison and Edmonds, Marie and Zahirovic, Sabin}, title = {Deep Carbon Cycling Over the Past 200 Million Years: A Review of Fluxes in Different Tectonic Settings}, series = {Frontiers in Earth Science}, volume = {7}, journal = {Frontiers in Earth Science}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {2296-6463}, doi = {10.3389/feart.2019.00263}, pages = {22}, year = {2019}, language = {en} } @misc{HudsonBotzen2019, author = {Hudson, Paul and Botzen, W. J. Wouter}, title = {Cost-benefit analysis of flood-zoning policies: A review of current practice}, series = {Wiley Interdisciplinary Reviews : Water}, volume = {6}, journal = {Wiley Interdisciplinary Reviews : Water}, number = {6}, publisher = {Wiley}, address = {Hoboken}, issn = {2049-1948}, doi = {10.1002/wat2.1387}, pages = {21}, year = {2019}, abstract = {One commonly proposed method to limit flood risk is land-use or zoning policies which regulates construction in high-risk areas, in order to reduce economic exposure and its vulnerability to flood events. Although such zoning regulations can be effective in limiting trends in flood risk, they also have adverse impacts on society, for instance by limiting local development of areas near the water. In order to judge whether proposed land-use or zoning policies are a net benefit to society, they should be accepted or rejected based on a societal cost-benefit analysis (CBA). However, conducting a CBA of zoning regulation is complex and comprehensive guidelines of how to do such an analysis are lacking. We offer guidelines for good practice. In order to assess the costs and benefits of zoning as a climate change adaption strategy, they should be assessed at a societal level in order to account for public good features of flood risk reduction strategies, and because costs in one area can be benefits in another region. We propose a multistep process: first, determine the spatial extent of the zoning policy and how interconnected the zoned area is to other locations; second, conduct a CBA using monetary costs and benefits estimated from an integrated hydro-economic model to investigate if total benefits exceed total costs; third, conduct a sensitivity analysis regarding the main assumptions; fourth, conduct a multicriteria analysis (MCA) of the normative outcomes of a zoning policy. A desirable policy is preferred in both the CBA and MCA. This article is categorized under: Engineering Water > Planning Water Human Water > Value of Water Science of Water > Water Extremes Human Water > Methods}, language = {en} } @article{LeonCardonaMejiaVelezetal.2019, author = {Le{\´o}n, Santiago and Cardona, Agust{\´i}n and Mejia Velez, Dany and Botello, G. E. and Villa, V{\´i}ctor and Collo, Gilda and Valencia, Victor A. and Zapata, Sebastian Henao and Avellaneda-Jimenez, D. S.}, title = {Source area evolution and thermal record of an Early Cretaceous back-arc basin along the northwesternmost Colombian Andes}, series = {Journal of South American earth sciences}, volume = {94}, journal = {Journal of South American earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {0895-9811}, doi = {10.1016/j.jsames.2019.102229}, pages = {16}, year = {2019}, abstract = {Identifying the provenance signature and geodynamic setting on which sedimentary basins at convergent margins grow is challenging since they result from coupled erosional and tectonic processes, which shape the evolution of source areas and the stress regime. The Early Cretaceous evolution of the northern Andes of Colombia is characterized by extensional tectonics and the subsequent formation of a marginal basin. The Abejorral Formation and coeval volcano-sedimentary rocks are exposed along the western flank and axis of the Central Cordillera. They comprise an Early Cretaceous transgressive sequence initially accumulated in fluvial deltaic environments, which switched towards a deep-marine setting, and are interpreted as the infilling record of a marginal back-arc basin. Available provenance data suggest that Permian-Triassic metamorphic and less abundant Jurassic magmatic rocks forming the basement of the Central Cordillera sourced the Abejorral Formation. New detailed volcanic and metamorphic lithics analyses, conventional and varietal study of heavy minerals, detrital rutile mineral chemistry, allowed us to document changes in the source areas defined by the progressive appearance of both higher-grade and more distal low-grade metamorphic sources, which switched from pelitic to dominantly mafic in composition. Crystallochemical indexes of clay minerals of fine-grained rocks of the Abejorral Formation suggest that samples located close to the Romeral Fault System show characteristics of low-medium P-T low-grade metamorphism, whereas rocks located farther to the northeast preserve primary diagenetic features, which suggest a high heat-flow accumulation setting. We interpret that the Abejorral Formation records the progressive unroofing of the Central Cordillera basement that was being rapidly exhumed, as well as the incorporation of distal subduction-related metamorphic complexes to the west in response either to the widening of extensional front or the reactivation of fault structures on the oceanward margin of the basin. Although the deformational record of the Abejorral Formation would have resulted from over-imposed episodes, our new geochronological constraints suggest that this sedimentary sequence must have been deformed before the Paleocene due to the presence of arc-related intrusive non-deformed magmatic rocks with a crystallization age of ca. 60 Ma.}, language = {en} } @article{Iturrizaga2019, author = {Iturrizaga, Lasafam}, title = {Historical beacon fire lines as early warning systems for glacier lake outbursts in the Hindu Kush-Karakoram Mountains}, series = {Natural hazards : journal of the International Society for the Prevention and Mitigation of Natural Hazards}, volume = {99}, journal = {Natural hazards : journal of the International Society for the Prevention and Mitigation of Natural Hazards}, number = {1}, publisher = {Springer}, address = {New York}, issn = {0921-030X}, doi = {10.1007/s11069-019-03705-1}, pages = {39 -- 70}, year = {2019}, abstract = {The paper presents a historical long-distance communication system based on beacon fires in one of the most dynamic and rugged mountain ranges of the world, the Hindu Kush-Karakoram-Himalayas. It was deployed as an early warning system for glacial lake outburst floods, which caused devastating impacts on settlement zones and infrastructure until the middle of the twentieth century. The study revealed that the beacon fire systems were operated in distinct valleys spread over the entire Hindu Kush-Karakoram Region. The remarkable fact is the establishment of fire posts in highly difficult accessible mountain environments with communication distances of several hundred kilometres for individual beacon lines. The warning system was a cooperative natural hazard management, which was operated even across distinct ethnic groups. Distant societies, formerly perceived as isolated villages by physical barriers of the high mountain relief, were in historical times connected not only by challenging trade routes but also by a fast working optical communication system. The findings are discussed in the context of a future sustainable natural hazard management.}, language = {en} } @article{McKibbinPittarelloMakaronaetal.2019, author = {McKibbin, Seann J. and Pittarello, Lidia and Makarona, Christina and Hamann, Christopher and Hecht, Lutz and Chernonozhkin, Stepan M. and Goderis, Steven and Claeys, Philippe}, title = {Petrogenesis of main group pallasite meteorites based on relationships among texture, mineralogy, and geochemistry}, series = {Meteoritics \& planetary science : journal of the Meteoritical Society}, volume = {54}, journal = {Meteoritics \& planetary science : journal of the Meteoritical Society}, number = {11}, publisher = {Wiley}, address = {Hoboken}, issn = {1086-9379}, doi = {10.1111/maps.13392}, pages = {2814 -- 2844}, year = {2019}, abstract = {Main group pallasite meteorites are samples of a single early magmatic planetesimal, dominated by metal and olivine but containing accessory chromite, sulfide, phosphide, phosphates, and rare phosphoran olivine. They represent mixtures of core and mantle materials, but the environment of formation is poorly understood, with a quiescent core-mantle boundary, violent core-mantle mixture, or surface mixture all recently suggested. Here, we review main group pallasite data sets and petrologic characteristics, and present new observations on the low-MnO pallasite Brahin that contains abundant fragmental olivine, but also rounded and angular olivine and potential evidence of sulfide-phosphide liquid immiscibility. A reassessment of the literature shows that low-MnO and high-FeO subgroups preferentially host rounded olivine and low-temperature P2O5-rich phases such as the Mg-phosphate farringtonite and phosphoran olivine. These phases form after metal and silicate reservoirs back-react during decreasing temperature after initial separation, resulting in oxidation of phosphorus and chromium. Farringtonite and phosphoran olivine have not been found in the common subgroup PMG, which are mechanical mixtures of olivine, chromite with moderate Al2O3 contents, primitive solid metal, and evolved liquid metal. Lower concentrations of Mn in olivine of the low-MnO PMG subgroup, and high concentrations of Mn in low-Al2O3 chromites, trace the development and escape of sulfide-rich melt in pallasites and the partially chalcophile behavior for Mn in this environment. Pallasites with rounded olivine indicate that the core-mantle boundary of their planetesimal may not be a simple interface but rather a volume in which interactions between metal, silicate, and other components occur.}, language = {en} } @article{LescoutreTugendBruneetal.2019, author = {Lescoutre, Rodolphe and Tugend, Julie and Brune, Sascha and Masini, Emmanuel and Manatschal, Gianreto}, title = {Thermal Evolution of Asymmetric Hyperextended Magma-Poor Rift Systems: Results From Numerical Modeling and Pyrenean Field Observations}, series = {Geochemistry, geophysics, geosystems}, volume = {20}, journal = {Geochemistry, geophysics, geosystems}, number = {10}, publisher = {American Geophysical Union}, address = {Washington}, issn = {1525-2027}, doi = {10.1029/2019GC008600}, pages = {4567 -- 4587}, year = {2019}, abstract = {We investigate the thermal and structural evolution of asymmetric rifted margin using numerical modeling and geological observations derived from the Western Pyrenees. Our numerical model provides a self-consistent physical evolution of the top basement heat flow during asymmetric rifting. The model shows a pronounced thermal asymmetry that is caused by migration of the rift center toward the upper plate. The same process creates a diachronism for the record of maximum heat flow and maximum temperatures (T-max) in basal rift sequences. The Mauleon-Arzacq basin (W-Pyrenees) corresponds to a former mid-Cretaceous asymmetric hyperextended rift basin. New vitrinite reflectance data in addition to existing data sets from this basin reveal an asymmetry in the distribution of peak heat (T-max) with respect to the rift shoulders, where highest values are located at the former upper- to lower-plate transition. This data set from the Arzacq-Mauleon field study confirms for the first time the thermal asymmetry predicted by numerical models. Numerical modeling results also suggest that complexities in synrift thermal architecture could arise when hanging-wall-derived extensional allochthons and related T-max become part of the lower plate and are transported away from the upper- to lower-plate transition. This study emphasizes the limitations of the common approach to integrate punctual thermal data from pre-rift to synrift sedimentary sequences in order to describe the rift-related thermal evolution and paleothermal gradients at the scale of a rift basin or a rifted margin.}, language = {en} } @article{TofeldeBufeTurowski2022, author = {Tofelde, Stefanie and Bufe, Aaron and Turowski, Jens M.}, title = {Hillslope Sediment Supply Limits Alluvial Valley Width}, series = {AGU Advances}, journal = {AGU Advances}, publisher = {American Geophysical Union (AGU); Wiley}, address = {Hoboken, New Jersey, USA}, issn = {2576-604X}, doi = {10.1029/2021AV000641}, pages = {20}, year = {2022}, abstract = {River-valley morphology preserves information on tectonic and climatic conditions that shape landscapes. Observations suggest that river discharge and valley-wall lithology are the main controls on valley width. Yet, current models based on these observations fail to explain the full range of cross-sectional valley shapes in nature, suggesting hitherto unquantified controls on valley width. In particular, current models cannot explain the existence of paired terrace sequences that form under cyclic climate forcing. Paired river terraces are staircases of abandoned floodplains on both valley sides, and hence preserve past valley widths. Their formation requires alternating phases of predominantly river incision and predominantly lateral planation, plus progressive valley narrowing. While cyclic Quaternary climate changes can explain shifts between incision and lateral erosion, the driving mechanism of valley narrowing is unknown. Here, we extract valley geometries from climatically formed, alluvial river-terrace sequences and show that across our dataset, the total cumulative terrace height (here: total valley height) explains 90\%-99\% of the variance in valley width at the terrace sites. This finding suggests that valley height, or a parameter that scales linearly with valley height, controls valley width in addition to river discharge and lithology. To explain this valley-width-height relationship, we reformulate existing valley-width models and suggest that, when adjusting to new boundary conditions, alluvial valleys evolve to a width at which sediment removal from valley walls matches lateral sediment supply from hillslope erosion. Such a hillslope-channel coupling is not captured in current valley-evolution models. Our model can explain the existence of paired terrace sequences under cyclic climate forcing and relates valley width to measurable field parameters. Therefore, it facilitates the reconstruction of past climatic and tectonic conditions from valley topography.}, language = {en} } @article{OberhaensliBousquetGoffe2003, author = {Oberh{\"a}nsli, Roland and Bousquet, Romain and Goffe, B.}, title = {Comment to "Chloritoid composition and formation in the eastern Central Alps : a comparison between Penninic and Helvetic occurrences" by M. Rahn, M. Steinmann and M. Frey}, issn = {0036-7699}, year = {2003}, language = {en} } @phdthesis{Demory2004, author = {Demory, Fran{\c{c}}ois}, title = {Paleomagnetic dating of climatic events in Late Quaternary sediments of Lake Baikal (Siberia)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001720}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {Der Baikalsee ist ein ideales Klimaarchiv f{\"u}r die Mitte Eurasiens. In dieser Arbeit wurde gesteinsmagnetische und paleomagnetische Analysen an hemipelagischen Sequenzen von vier Lokationen analysiert. Die Kerne erreichen ein Alter von maximal 300 ky. In Kombination mit TEM, XRD, XRF und geochemischen Analysen zeigt die gesteinsmagnetische Studie, dass detritischer Magnetit das magnetische Signal der glazialen Sedimente dominiert. Die magnetischen Signale der interglazialen Sedimente wurden durch diagenetische Prozesse ver{\"a}ndert. Mittels HIRM k{\"o}nnen H{\"a}matit und Goethit quantifiziert werden. Diese Methode eignet sich, den detritischen Eintrag in den Baikalsee abzusch{\"a}tzen. Relative Paleointensit{\"a}ten des Erdmagnetfeldes ergaben reproduizerbare Muster, welche in Korrelation mit gutdatierten Referenzproben die Ableitung eines alternativen Altersmodells f{\"u}r die Datierung der Baikalsedimente erm{\"o}glichten. Bei Anwendung des paleomagnetischen Altersmodells beobachtet man, dass die Abk{\"u}hlung im Baikalgebiet und im Oberfl{\"a}chenwasser des Nordatlantiks wie sie aus den \&\#948;18 O-Werten planktonischer Foraminiferen abgeleitet werden kann, zeitgleich ist. Wird das aus benthischen \&\#948;18 O-Werten abgeleitete Altermdodell auf den Baikalsee angewandt, ergibt sich eine deutliche Zeitverschiebung. Das benthische Altersmodell repr{\"a}sentiert die globale Ver{\"a}nderung des Eisvolumens, welche sp{\"a}ter als die V{\"a}nderung der Oberfl{\"a}chenwassertemperatur auftritt. Die Kompilation paleomagnetischer Kurven ergab eine neue relative Paleointensit{\"a}tskurve \“Baikal 200\”. Mittels Korngr{\"o}ssenanalyse des Detritus konnten drei Faziestypen mit unterschiedlicher Sedimentationsdynamik unterschieden werden: 1) Glaziale Peroiden werden durch hohe Tongehalte infolge von Windeintrag und durch grobe Sandfraktion mittels Transport durch lokale Winde {\"u}ber das Eis charakterisiert. Dieser Faziestyp deutet auf arides Klima. 2) W{\"a}hrend der Glazial/Interglazial-{\"U}berg{\"a}nge steigt die Siltfraktion an. Dies deutet auf erh{\"o}hte Feuchtigkeit und damit verbunden erh{\"o}hte Sedimentdynamik. Windtransport und in den Schnee der Eisdecke eingetragener Staub sind die vorherrschenden Prozesse, welche den Silt in hemipelagischer Position zur Ablagerung bringen. 3) W{\"a}hrend des klimatischen Optimum des Eeemian werden Gr{\"o}sse und Quantit{\"a}t des Silts minimal, was auf eine geschlossene Vegetationsdecke im Hinterland deutet.}, language = {en} } @article{ParkLuehrKervalishvilietal.2015, author = {Park, Jaeheung and L{\"u}hr, Hermann and Kervalishvili, Guram N. and Rauberg, Jan and Michaelis, Ingo and Stolle, Claudia and Kwak, Young-Sil}, title = {Nighttime magnetic field fluctuations in the topside ionosphere at midlatitudes and their relation to medium-scale traveling ionospheric disturbances: The spatial structure and scale sizes}, series = {Journal of geophysical research : Space physics}, volume = {120}, journal = {Journal of geophysical research : Space physics}, number = {8}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2015JA021315}, pages = {6818 -- 6830}, year = {2015}, abstract = {Previous studies suggested that electric and/or magnetic field fluctuations observed in the nighttime topside ionosphere at midlatitudes generally originate from quiet time nocturnal medium-scale traveling ionospheric disturbances (MSTIDs). However, decisive evidences for the connection between the two have been missing. In this study we make use of the multispacecraft observations of midlatitude magnetic fluctuations (MMFs) in the nighttime topside ionosphere by the Swarm constellation. The analysis results show that the area hosting MMFs is elongated in the NW-SE (NE-SW) direction in the Northern (Southern) Hemisphere. The elongation direction and the magnetic field polarization support that the area hosting MMFs is nearly field aligned. All these properties of MMFs suggest that they have close relationship with MSTIDs. Expectation values of root-mean-square field-aligned currents associated with MMFs are up to about 4nA/m(2). MMF coherency significantly drops for longitudinal distances of 1 degrees.}, language = {en} } @article{BenardKlimmWoodlandetal.2018, author = {Benard, Antoine and Klimm, Kevin and Woodland, Alan B. and Arculus, Richard J. and Wilke, Max and Botcharnikov, Roman E. and Shimizu, Nobumichi and Nebel, Oliver and Rivard, Camille and Ionov, Dmitri A.}, title = {Oxidising agents in sub-arc mantle melts link slab devolatilisation and arc magmas}, series = {Nature Communications}, volume = {9}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-018-05804-2}, pages = {10}, year = {2018}, abstract = {Subduction zone magmas are more oxidised on eruption than those at mid-ocean ridges. This is attributed either to oxidising components, derived from subducted lithosphere (slab) and added to the mantle wedge, or to oxidation processes occurring during magma ascent via differentiation. Here we provide direct evidence for contributions of oxidising slab agents to melts trapped in the sub-arc mantle. Measurements of sulfur (S) valence state in sub-arc mantle peridotites identify sulfate, both as crystalline anhydrite (CaSO4) and dissolved SO42- in spinel-hosted glass (formerly melt) inclusions. Copper-rich sulfide precipitates in the inclusions and increased Fe3+/Sigma Fe in spinel record a S6+-Fe2+ redox coupling during melt percolation through the sub-arc mantle. Sulfate-rich glass inclusions exhibit high U/Th, Pb/Ce, Sr/Nd and delta S-34 (+ 7 to + 11\%), indicating the involvement of dehydration products of serpentinised slab rocks in their parental melt sources. These observations provide a link between liberated slab components and oxidised arc magmas.}, language = {en} } @article{FerreroAngel2018, author = {Ferrero, Silvio and Angel, Ross J.}, title = {Micropetrology}, series = {Journal of petrology}, volume = {59}, journal = {Journal of petrology}, number = {9}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0022-3530}, doi = {10.1093/petrology/egy075}, pages = {1671 -- 1700}, year = {2018}, abstract = {Inclusions in minerals, whether fluids, melts or crystalline phases, are small pieces of the large-scale puzzle of Nature, time-consuming to investigate and often of difficult interpretation. Yet they are windows into the past of their host mineral. Mineral inclusions provide the opportunity to unravel the genesis of their host, and the increasingly refined understanding of their elastic behaviour provides the basis for alternative, equilibrium-independent geobarometry. Fluid and melt inclusions reveal information about material transfer in the Earth system, from shallow mineralization to mantle re-fertilization via subduction. The study of inclusions is thus one of the most intriguing and fertile branches of micropetrology. In this contribution, we focus on two recent developments: the use of elasticity models to extract the formation conditions of the host crystal, and the discovery and investigation of melt inclusions in metamorphic rocks. We also discuss how to evaluate the information provided by inclusions, given that they are no longer at the pressure and temperature conditions of entrapment. We discuss how to understand and quantify the changes undergone during cooling and depressurization, and how metastability-related phenomena in inclusions, such as crystallization of rare polymorphs and preservation of the original content of volatiles in fluid and melt inclusions, provide direct evidence that inclusions represent closed systems. The field of study of inclusions in minerals still has a largely untapped potential. The most fruitful avenues for future research will emerge from continuous technological innovation in analytical and imaging techniques, the application of experimental petrology, and the development and application of new theoretical models for coupled mineral behaviour under changing P-T conditions.}, language = {en} } @article{TotzTzipermanCoumouetal.2017, author = {Totz, Sonja Juliana and Tziperman, Eli and Coumou, Dim and Pfeiffer, Karl and Cohen, Judah}, title = {Winter precipitation forecast in the European and mediterranean regions using cluster analysis}, series = {Geophysical research letters}, volume = {44}, journal = {Geophysical research letters}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1002/2017GL075674}, pages = {12418 -- 12426}, year = {2017}, abstract = {The European climate is changing under global warming, and especially the Mediterranean region has been identified as a hot spot for climate change with climate models projecting a reduction in winter rainfall and a very pronounced increase in summertime heat waves. These trends are already detectable over the historic period. Hence, it is beneficial to forecast seasonal droughts well in advance so that water managers and stakeholders can prepare to mitigate deleterious impacts. We developed a new cluster-based empirical forecast method to predict precipitation anomalies in winter. This algorithm considers not only the strength but also the pattern of the precursors. We compare our algorithm with dynamic forecast models and a canonical correlation analysis-based prediction method demonstrating that our prediction method performs better in terms of time and pattern correlation in the Mediterranean and European regions.}, language = {en} } @article{GaedkeKlauschies2017, author = {Gaedke, Ursula and Klauschies, Toni}, title = {Analyzing the shape of observed trait distributions enables a data-based moment closure of aggregate models}, series = {Limnology and Oceanography: Methods}, volume = {15}, journal = {Limnology and Oceanography: Methods}, publisher = {Wiley}, address = {Hoboken}, issn = {1541-5856}, doi = {10.1002/lom3.10218}, pages = {979 -- 994}, year = {2017}, abstract = {The shape of trait distributions may inform about the selective forces that structure ecological communities. Here, we present a new moment-based approach to classify the shape of observed biomass-weighted trait distributions into normal, peaked, skewed, or bimodal that facilitates spatio-temporal and cross-system comparisons. Our observed phytoplankton trait distributions exhibited substantial variance and were mostly skewed or bimodal rather than normal. Additionally, mean, variance, skewness und kurtosis were strongly correlated. This is in conflict with trait-based aggregate models that often assume normally distributed trait values and small variances. Given these discrepancies between our data and general model assumptions we used the observed trait distributions to test how well different aggregate models with first- or second-order approximations and different types of moment closure predict the biomass, mean trait, and trait variance dynamics using weakly or moderately nonlinear fitness functions. For weakly non-linear fitness functions aggregate models with a second-order approximation and a data-based moment closure that relied on the observed correlations between skewness and mean, and kurtosis and variance predicted biomass and often also mean trait changes fairly well and better than models with first-order approximations or a normal-based moment closure. In contrast, none of the models reflected the changes of the trait variances reliably. Aggregate model performance was often also poor for moderately nonlinear fitness functions. This questions a general applicability of the normal-based approach, in particular for predicting variance dynamics determining the speed of trait changes and maintenance of biodiversity. We evaluate in detail how and why better approximations can be obtained.}, language = {en} } @article{SebagGarcinAdatteetal.2018, author = {Sebag, David and Garcin, Yannick and Adatte, Thierry and Deschamps, Pierre and Menot, Guillemette and Verrecchia, Eric P.}, title = {Correction for the siderite effect on Rock-Eval parameters}, series = {Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry}, volume = {123}, journal = {Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry}, publisher = {Elsevier}, address = {Oxford}, issn = {0146-6380}, doi = {10.1016/j.orggeochem.2018.05.010}, pages = {126 -- 135}, year = {2018}, abstract = {Originally developed for use in the petroleum industry, Rock-Eval pyrolysis is a technique commonly applied to lake sediments to infer paleoenvironmental reconstructions. The standard Rock-Eval parameters provide information on the amount of total organic and inorganic carbon (TOC and MinC, respectively), and are usually interpreted as proxies for the source (aquatic or terrestrial) of the primary production of organic matter (Hydrogen Index vs Oxygen Index). Although this method usually provides valuable evidence, the common presence of siderite in tropical lake sediments can alter the primary signal of the sedimentary organic matter (SOM). Indeed, the CO2 and CO released by the pyrolysis of siderite are integral to the calculation of the SOM-related standard Rock-Eval parameters. In this study, we analyze sediments from a core collected in the Lake Barombi (southwest Cameroon) and describe the impact of siderite on standard Rock-Eval parameters. We propose a workflow that allows standard Rock-Eval parameters to be corrected, based on the analysis of thermograms. The proposed corrections provide siderite-effect-free parameters, accurately reflecting the changes in sedimentary organic matter composition. (C) 2018 Elsevier Ltd. All rights reserved.}, language = {en} } @article{TrauthFoersterJungingeretal.2018, author = {Trauth, Martin H. and Foerster, Verena and Junginger, Annett and Asrat, Asfawossen and Lamb, Henry F. and Sch{\"a}bitz, Frank}, title = {Abrupt or gradual?}, series = {Quaternary research : an interdisciplinary journal}, volume = {90}, journal = {Quaternary research : an interdisciplinary journal}, number = {2}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0033-5894}, doi = {10.1017/qua.2018.30}, pages = {321 -- 330}, year = {2018}, abstract = {We used a change point analysis on a late Pleistocene-Holocene lake-sediment record from the Chew Bahir basin in the southern Ethiopian Rift to determine the amplitude and duration of past climate transitions. The most dramatic changes occurred over 240 yr (from similar to 15,700 to 15,460 yr) during the onset of the African Humid Period (AHP), and over 990 yr (from similar to 4875 to 3885 yr) during its protracted termination. The AHP was interrupted by a distinct dry period coinciding with the high-latitude Younger Dryas stadial, which had an abrupt onset (less than similar to 100 yr) at similar to 13,260 yr and lasted until similar to 11,730 yr. Wet-dry-wet transitions prior to the AHP may reflect the high-latitude Dansgaard-Oeschger cycles, as indicated by cross-correlation of the potassium record with the NorthGRIP ice core record between similar to 45-20 ka. These findings may contribute to the debates regarding the amplitude, and duration and mechanisms of past climate transitions, and their possible influence on the development of early modern human cultures.}, language = {en} } @article{XiongStollePark2018, author = {Xiong, Chao and Stolle, Claudia and Park, Jaeheung}, title = {Climatology of GPS signal loss observed by Swarm satellites}, series = {Annales geophysicae}, volume = {36}, journal = {Annales geophysicae}, number = {2}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {0992-7689}, doi = {10.5194/angeo-36-679-2018}, pages = {679 -- 693}, year = {2018}, abstract = {By using 3-year global positioning system (GPS) measurements from December 2013 to November 2016, we provide in this study a detailed survey on the climatology of the GPS signal loss of Swarm onboard receivers. Our results show that the GPS signal losses prefer to occur at both low latitudes between +/- 5 and +/- 20 degrees magnetic latitude (MLAT) and high latitudes above 60 degrees MLAT in both hemispheres. These events at all latitudes are observed mainly during equinoxes and December solstice months, while totally absent during June solstice months. At low latitudes the GPS signal losses are caused by the equatorial plasma irregularities shortly after sunset, and at high latitude they are also highly related to the large density gradients associated with ionospheric irregularities. Additionally, the high-latitude events are more often observed in the Southern Hemisphere, occurring mainly at the cusp region and along nightside auroral latitudes. The signal losses mainly happen for those GPS rays with elevation angles less than 20 degrees, and more commonly occur when the line of sight between GPS and Swarm satellites is aligned with the shell structure of plasma irregularities. Our results also confirm that the capability of the Swarm receiver has been improved after the bandwidth of the phase-locked loop (PLL) widened, but the updates cannot radically avoid the interruption in tracking GPS satellites caused by the ionospheric plasma irregularities. Additionally, after the PLL bandwidth increased larger than 0.5 Hz, some unexpected signal losses are observed even at middle latitudes, which are not related to the ionospheric plasma irregularities. Our results suggest that rather than 1.0 Hz, a PLL bandwidth of 0.5 Hz is a more suitable value for the Swarm receiver.}, language = {en} } @article{HeringStinnesbeckFolmeisteretal.2018, author = {Hering, Fabio and Stinnesbeck, Wolfgang and Folmeister, Jens and Frey, Eberhard and Stinnesbeck, Sarah and Aviles, Jeronimo and Nunez, Eugenio Aceves and Gonzalez, Arturo and Mata, Alejandro Terrazas and Benavente, Martha Elena and Rojas, Carmen and Morlet, Adriana Velazquez and Frank, Norbert and Zell, Patrick and Becker, Julia}, title = {The Chan Hol cave near Tulum (Quintana Roo, Mexico)}, series = {Journal of quaternary science}, volume = {33}, journal = {Journal of quaternary science}, number = {4}, publisher = {Wiley}, address = {Hoboken}, issn = {0267-8179}, doi = {10.1002/jqs.3025}, pages = {444 -- 454}, year = {2018}, abstract = {Numerous charcoal accumulations discovered in the submerged Chan Hol cave near Tulum, Quintana Roo, Mexico, have been C-14-dated revealing ages between 8110 +/- 28 C-14 a BP (9122-8999 cal a BP) and 7177 +/- 27 C-14 a BP (8027-7951 cal a BP). These charcoal concentrations, interpreted here as ancient illumination sites, provide strong evidence that the Chan Hol cave was dry and accessible during that time interval. Humans used the cave for at least 1200 years during the early and middle Holocene, before access was successively interrupted by global sea level rise and flooding of the cave system. Our data thus narrow the gap between an early settlement in the Tulum area reaching from the late Pleistocene (similar to 13 000 a) to middle Holocene (e.g. 7177 C-14 a BP), and the Maya Formative period at approximately 3000 a bp. Yet, no evidence has been presented to date for human settlement during the similar to 4000-year interval between 7000 and 3000 a. This is remarkable as settlement in other areas of south-eastern Mexico (e.g. Chiapas, Tabasco) and in Guatemala was apparently continuous.}, language = {en} } @article{KarbonBalidakisBeldaetal.2018, author = {Karbon, Maria and Balidakis, Kyriakos and Belda, Santiago and Nilsson, Tobias and Hagedoorn, Jan and Schuh, Harald}, title = {Long-Term evaluation of ocean tidal variation models of polar motion and UT1}, series = {Pure and applied geophysics}, volume = {175}, journal = {Pure and applied geophysics}, number = {5}, publisher = {Springer}, address = {Basel}, issn = {0033-4553}, doi = {10.1007/s00024-018-1866-1}, pages = {1611 -- 1629}, year = {2018}, abstract = {Recent improvements in the development of VLBI (very long baseline interferometry) and other space geodetic techniques such as the global navigation satellite systems (GNSS) require very precise a-priori information of short-period (daily and sub-daily) Earth rotation variations. One significant contribution to Earth rotation is caused by the diurnal and semi-diurnal ocean tides. Within this work, we developed a new model for the short-period ocean tidal variations in Earth rotation, where the ocean tidal angular momentum model and the Earth rotation variation have been setup jointly. Besides the model of the short-period variation of the Earth's rotation parameters (ERP), based on the empirical ocean tide model EOT11a, we developed also ERP models, that are based on the hydrodynamic ocean tide models FES2012 and HAMTIDE. Furthermore, we have assessed the effect of uncertainties in the elastic Earth model on the resulting ERP models. Our proposed alternative ERP model to the IERS 2010 conventional model considers the elastic model PREM and 260 partial tides. The choice of the ocean tide model and the determination of the tidal velocities have been identified as the main uncertainties. However, in the VLBI analysis all models perform on the same level of accuracy. From these findings, we conclude that the models presented here, which are based on a re-examined theoretical description and long-term satellite altimetry observation only, are an alternative for the IERS conventional model but do not improve the geodetic results.}, language = {en} } @article{WunderKutzschbachHosseetal.2018, author = {Wunder, Bernd and Kutzschbach, Martin and Hosse, Luisa and Wilke, Franziska Daniela Helena and Schertl, Hans-Peter and Chopin, Christian}, title = {Synthetic B-[4]-bearing dumortierite and natural B-[4]-free magnesiodumortierite from the Dora-Maira Massif}, series = {European journal of mineralogy}, volume = {30}, journal = {European journal of mineralogy}, number = {3}, publisher = {Schweizerbart}, address = {Stuttgart}, issn = {0935-1221}, doi = {10.1127/ejm/2018/0030-2742}, pages = {471 -- 483}, year = {2018}, abstract = {Dumortierite was synthesized in piston-cylinder experiments at 2.5-4.0 GPa, 650-700 degrees C in the Al2O3 -B2O3-SiO2-H2O (ABSH) system. Electron-microprobe (EMP) analyses reveal significant boron-excess (up to 0.26 B-[4] per formula unit, pfu) and silicon-deficiency relative to the ideal anhydrous dumortierite stoichiometry Al7BSi3O18 . The EMP data in conjunction with results from single-crystal Raman spectroscopy and powder X-ray diffraction provide evidence that silicon at the tetrahedral site is replaced by excess boron via the substitution Si-[4] <--> B-[4] + H. The Raman spectrum of synthetic dumortierite in the frequency region 2000 4000 cm(-1) comprises eight bands, of which six are located at frequencies below 3400 cm(-1). This points to strong hydrogen bonding, most likely O2-H center dot center dot center dot O7 and O7-H center dot center dot center dot O2, arising from a high number of octahedral vacancies at the All site and substitution of trivalent Al3+ and B3+ for Si4+ at Si1 and Si2 sites, causing decreasing acceptor-donor distances and lower incident valence at the acceptor oxygen. Contrary to the synthetic high-pressure ABSH-dumortierite, magnesiodumortierite from the Dora-Maira Massif, which is assumed to have formed at similar conditions (2.5-3.0 GPa, 700 degrees C), does not show any B-excess. Tourmaline shows an analogous behaviour in that magnesium-rich (e.g., dravitic) tourmaline formed at high pressure shows no or only minor amounts of tetrahedral boron, whereas natural aluminum-rich tourmaline and synthetic olenitic tourmaline formed at high pressures can incorporate significant amounts of tetrahedral boron. Two mechanisms might account for this discrepancy: (i) Structural avoidance of Mg-[6]-(OR3+)-R-[4] configurations in magnesiodumortierite due to charge deficieny at the oxygens O2 and O7 and strong local distortion of M1 due to decreased O2-O7 bond length, and/or (ii) decreasing fluid mobility of boron in Al-rich systems at high pressures.}, language = {en} }