@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{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{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} } @article{vanderMeijTemmeLinetal.2018, author = {van der Meij, Marijn W. and Temme, Arnaud J. A. M. and Lin, H. S. and Gerke, Horst H. and Sommer, Michael}, title = {On the role of hydrologic processes in soil and landscape evolution modeling}, series = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, volume = {185}, journal = {Earth science reviews : the international geological journal bridging the gap between research articles and textbooks}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-8252}, doi = {10.1016/j.earscirev.2018.09.001}, pages = {1088 -- 1106}, year = {2018}, abstract = {The ability of water to transport and transform soil materials is one of the main drivers of soil and landscape development. In turn, soil and landscape properties determine how water is distributed in soil landscapes. Understanding the complex dynamics of this co-evolution of soils, landscapes and the hydrological system is fundamental in adapting land management to changes in climate. Soil-Landscape Evolution Models (SLEMs) are used to simulate the development and evolution of soils and landscapes. However, many hydrologic processes, such as preferential flow and subsurface lateral flow, are currently absent in these models. This limits the applicability of SLEMs to improve our understanding of feedbacks in the hydro-pedo-geomorphological system. Implementation of these hydrologic processes in SLEMs faces several complications related to calculation demands, limited methods for linking pedogenic and hydrologic processes, and limited data on quantification of changes in the hydrological system over time. In this contribution, we first briefly review processes and feedbacks in soil-landscape-hydrological systems. Next, we elaborate on the development required to include these processes in SLEMs. We discuss the state-of-the-art knowledge, identify complications, give partial solutions and suggest important future development. The main requirements for incorporating hydrologic processes in SLEMs are: (1) designing a model framework that can deal with varying timescales for different sets of processes, (2) developing and implementing methods for simulating pedogenesis as a function of water flow, (3) improving and implementing knowledge on the evolution and dynamics of soil hydraulic properties over different timescales, and (4) improving the database on temporal changes and dynamics of flow paths.}, 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{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{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{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{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} } @article{YamazakiStolleMatzkaetal.2018, author = {Yamazaki, Yosuke and Stolle, Claudia and Matzka, J{\"u}rgen and Alken, Patrick}, title = {Quasi-6-Day Wave Modulation of the Equatorial Electrojet}, series = {Journal of geophysical research : Space physics}, volume = {123}, journal = {Journal of geophysical research : Space physics}, number = {5}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1029/2018JA025365}, pages = {4094 -- 4109}, year = {2018}, abstract = {The equatorial electrojet is an enhanced eastward current in the dayside E region ionosphere flowing along the magnetic equator. The equatorial electrojet is highly variable as it is subject to various forcing mechanisms including atmospheric waves from the lower layers of the atmosphere. There are occasionally times when the intensity of the equatorial electrojet at a fixed longitude shows an oscillatory variation with a period of approximately 6days. We present case studies of such events based on the equatorial electrojet measurements from the CHAMP and Swarm satellites. The spatial and temporal variability of the equatorial electrojet intensity during these events reveals characteristics of a westward propagating wave with zonal wavenumber 1, consistent with the effect of the quasi-6-day planetary wave. Analyses of the geopotential height data from the Aura satellite confirm the presence of the quasi-6-day planetary wave in the lower thermosphere during the events. The amplitude of the quasi-6-day variation in the equatorial electrojet intensity depends on longitude, but no systematic longitudinal dependence is found for different events. During the event of August 2010, quasi-6-day variations are also observed by ground-based magnetometers and a radar in the Peruvian sector. The effect of the quasi-6-day wave accounts for up to +/- 5.9m/s in the equatorial vertical plasma velocity at noon, which is much larger than previously predicted by a numerical model. These results suggest that the quasi-6-day planetary wave is an important source of short-term variability in the equatorial ionosphere.}, language = {en} } @article{GlosseFegerMutigetal.2018, author = {Glosse, Philipp and Feger, Martina and Mutig, Kerim and Chen, Hong and Hirche, Frank and Hasan, Ahmed Abdallah Abdalrahman Mohamed and Gaballa, Mohamed Mahmoud Salem Ahmed and Hocher, Berthold and Lang, Florian and F{\"o}ller, Michael}, title = {AMP-activated kinase is a regulator of fibroblast growth factor 23 production}, series = {Kidney international : official journal of the International Society of Nephrology}, volume = {94}, journal = {Kidney international : official journal of the International Society of Nephrology}, number = {3}, publisher = {Elsevier}, address = {New York}, issn = {0085-2538}, doi = {10.1016/j.kint.2018.03.006}, pages = {491 -- 501}, year = {2018}, abstract = {Fibroblast growth factor 23 (FGF23) is a proteohormone regulating renal phosphate transport and vitamin D metabolism as well as inducing left heart hypertrophy. FGF23-deficient mice suffer from severe tissue calcification, accelerated aging and a myriad of aging-associated diseases. Bone cells produce FGF23 upon store-operated calcium ion entry (SOCE) through the calcium selective ion channel Orai1. AMP-activated kinase (AMPK) is a powerful energy sensor helping cells survive states of energy deficiency, and AMPK down-regulates Orai1. Here we investigated the role of AMPK in FGF23 production. Fgf23 gene transcription was analyzed by qRT-PCR and SOCE by fluorescence optics in UMR106 osteoblast-like cells while the serum FGF23 concentration and phosphate metabolism were assessed in AMPKa1-knockout and wild-type mice. The AMPK activator, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) down-regulated, whereas the AMPK inhibitor, dorsomorphin dihydrochloride (compound C) and AMPK gene silencing induced Fgf23 transcription. AICAR decreased membrane abundance of Orai1 and SOCE. SOCE inhibitors lowered Fgf23 gene expression induced by AMPK inhibition. AMPKa1-knockout mice had a higher serum FGF23 concentration compared to wild-type mice. Thus, AMPK participates in the regulation of FGF23 production in vitro and in vivo. The inhibitory effect of AMPK on FGF23 production is at least in part mediated by Orai1-involving SOCE.}, language = {en} } @article{KaiserOldorffBreitbachetal.2018, author = {Kaiser, Knut and Oldorff, Silke and Breitbach, Carsten and Kappler, Christoph and Theuerkauf, Martin and Scharnweber, Tobias and Schult, Manuela and Kuester, Mathias and Engelhardt, Christof and Heinrich, Ingo and Hupfer, Michael and Schwalbe, Grit and Kirschey, Tom and Bens, Oliver}, title = {A submerged pine forest from the early Holocene in the Mecklenburg Lake District, northern Germany}, series = {Boreas}, volume = {47}, journal = {Boreas}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {0300-9483}, doi = {10.1111/bor.12314}, pages = {910 -- 925}, year = {2018}, abstract = {For the first time, evidence of a submerged pine forest from the early Holocene can be documented in a central European lake. Subaquatic tree stumps were discovered in Lake Giesenschlagsee at a depth of between 2 and 5m using scuba divers, side-scan sonar and a remotely operated vehicle. Several erect stumps, anchored to the ground by roots, represent an insitu record of this former forest. Botanical determination revealed the stumps to be Scots pine (Pinus sylvestris) with an individual tree age of about 80years. The trees could not be dated by means of dendrochronology, as they are older than the regional reference chronology for pine. Radiocarbon ages from the wood range from 10880 +/- 210 to 10370 +/- 130cal. a BP, which is equivalent to the mid-Preboreal to early Boreal biozones. The trees are rooted in sedge peat, which can be dated to this period as well, using pollen stratigraphical analysis. Tilting of the peat bed by 4m indicates subsidence of the ground due to local dead ice melting, causing the trees to become submerged and preserved for millennia. Together with recently detected Lateglacial insitu tree occurrences in nearby lakes, the submerged pine forest at Giesenschlagsee represents a new and highly promising type of geo-bio-archive for the wider region. Comparable insitu pine remnants occur at some terrestrial (buried setting) and marine (submerged setting) sites in northern central Europe and beyond, but they partly differ in age. In general, the insitu pine finds document shifts of the zonal boreal forest ecosystem during the late Quaternary.}, language = {en} } @article{SchildgenvanderBeekSinclairetal.2018, author = {Schildgen, Taylor F. and van der Beek, Pieter A. and Sinclair, Hugh D. and Thiede, Rasmus Christoph}, title = {Spatial correlation bias in late-Cenozoic erosion histories derived from thermochronology}, series = {Nature : the international weekly journal of science}, volume = {559}, journal = {Nature : the international weekly journal of science}, number = {7712}, publisher = {Nature Publ. Group}, address = {London}, issn = {0028-0836}, doi = {10.1038/s41586-018-0260-6}, pages = {89 -- 93}, year = {2018}, abstract = {The potential link between erosion rates at the Earth's surface and changes in global climate has intrigued geoscientists for decades1,2 because such a coupling has implications for the influence of silicate weathering3,4 and organic-carbon burial5 on climate and for the role of Quaternary glaciations in landscape evolution1,6. A global increase in late-Cenozoic erosion rates in response to a cooling, more variable climate has been proposed on the basis of worldwide sedimentation rates7. Other studies have indicated, however, that global erosion rates may have remained steady, suggesting that the reported increases in sediment-accumulation rates are due to preservation biases, depositional hiatuses and varying measurement intervals8,9,10. More recently, a global compilation of thermochronology data has been used to infer a nearly twofold increase in the erosion rate in mountainous landscapes over late-Cenozoic times6. It has been contended that this result is free of the biases that affect sedimentary records11, although others have argued that it contains biases related to how thermochronological data are averaged12 and to erosion hiatuses in glaciated landscapes13. Here we investigate the 30 locations with reported accelerated erosion during the late Cenozoic6. Our analysis shows that in 23 of these locations, the reported increases are a result of a spatial correlation bias—that is, combining data with disparate exhumation histories, thereby converting spatial erosion-rate variations into temporal increases. In four locations, the increases can be explained by changes in tectonic boundary conditions. In three cases, climatically induced accelerations are recorded, driven by localized glacial valley incision. Our findings suggest that thermochronology data currently have insufficient resolution to assess whether late-Cenozoic climate change affected erosion rates on a global scale. We suggest that a synthesis of local findings that include location-specific information may help to further investigate drivers of global erosion rates.}, language = {en} } @article{KetenogluSpiekermannHarderetal.2018, author = {Ketenoglu, Didem and Spiekermann, Georg and Harder, Manuel and Oz, Erdinc and Koz, Cevriye and Yagci, Mehmet C. and Yilmaz, Eda and Yin, Zhong and Sahle, Christoph J. and Detlefs, Blanka and Yavas, Hasan}, title = {X-ray Raman spectroscopy of lithium-ion battery electrolyte solutions in a flow cell}, series = {Journal of synchrotron radiation}, volume = {25}, journal = {Journal of synchrotron radiation}, publisher = {International Union of Crystallography}, address = {Chester}, issn = {0909-0495}, doi = {10.1107/S1600577518001662}, pages = {537 -- 542}, year = {2018}, abstract = {The effects of varying LiPF6 salt concentration and the presence of lithium bis(oxalate)borate additive on the electronic structure of commonly used lithium-ion battery electrolyte solvents (ethylene carbonate-dimethyl carbonate and propylene carbonate) have been investigated. X-ray Raman scattering spectroscopy (a non-resonant inelastic X-ray scattering method) was utilized together with a closed-circle flow cell. Carbon and oxygen K-edges provide characteristic information on the electronic structure of the electrolyte solutions, which are sensitive to local chemistry. Higher Li+ ion concentration in the solvent manifests itself as a blue-shift of both the pi* feature in the carbon edge and the carbonyl pi* feature in the oxygen edge. While these oxygen K-edge results agree with previous soft X-ray absorption studies on LiBF4 salt concentration in propylene carbonate, carbon K-edge spectra reveal a shift in energy, which can be explained with differing ionic conductivities of the electrolyte solutions.}, language = {en} } @article{RizzoLauritaAltenberger2018, author = {Rizzo, Giovanna and Laurita, Salvatore and Altenberger, Uwe}, title = {The Timpa delle Murge ophiolitic gabbros, southern Apennines}, series = {Periodico di Mineralogia}, volume = {87}, journal = {Periodico di Mineralogia}, number = {1}, publisher = {Edizioni nuova cultura}, address = {Roma}, issn = {0369-8963}, doi = {10.2451/2018PM741}, pages = {5 -- 20}, year = {2018}, abstract = {The Timpa delle Murge ophiolite in the North Calabrian Unit is part of the Liguride Complex (southern Apennines). The study is concentrated on the gabbroic part of the ophiolite of the Pollino area. They preserve the high-grade ocean floor metamorphic and locally developed flaser textures under ocean floor conditions. The primary magmatic assemblages are clinopyroxene, plagioclase, and opaques. Brown hornblende is a late magmatic phase. Green hornblende, actinolite, albite, chlorite and epidote display metamorphic recrystallization under lower amphibolite facies conditions, followed by greenschist facies. The gabbros show subalkaline near to alkaline character with a tendency to a more calkalkaline trend. The normalization to primitive mantle and mid-ocean ridge basalt (N-MORB) compositions indicates a considerable depletion in Nb, P, Zr and Ti and an enrichment in Ba, Rb, K, Sr and Eu. This points to a mantle source, which is not compatible with a "normal" mid-ocean ridge situation. Rather, the gabbros are generated from a N-MORB-like melt with a strong crustal component, which was influenced by subduction related fluids and episodic melting during mid-ocean-ridge processes. Plausible geodynamic settings of the Timpa delle Murge gabbros are oceanic back-arc positions with embryonic MORB-activities. Similar slab contaminated magmatism is also known from the early stage of island arc formation in supra-subduction zone environments like the Izu-Bonin-Mariana island arc.}, language = {en} } @article{WanXiongRodriguezZuluagaetal.2018, author = {Wan, Xin and Xiong, Chao and Rodriguez-Zuluaga, Juan and Kervalishvili, Guram N. and Stolle, Claudia and Wang, Hui}, title = {Climatology of the Occurrence Rate and Amplitudes of Local Time Distinguished Equatorial Plasma Depletions Observed by Swarm Satellite}, series = {Journal of geophysical research : Space physics}, volume = {123}, journal = {Journal of geophysical research : Space physics}, number = {4}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2017JA025072}, pages = {3014 -- 3026}, year = {2018}, abstract = {In this study, we developed an autodetection technique for the equatorial plasma depletions (EPDs) and their occurrence and depletion amplitudes based on in situ electron density measurements gathered by Swarm A satellite. For the first time, comparisons are made among the detected EPDs and their amplitudes with the loss of Global Positioning System (GPS) signal of receivers onboard Swarm A, and the Swarm Level-2 product, Ionospheric Bubble Index (IBI). It has been found that the highest rate of EPD occurrence takes place generally between 2200 and 0000 magnetic local time (MLT), in agreement with the IBI. However, the largest amplitudes of EPD are detected earlier at about 1900-2100 MLT. This coincides with the moment of higher background electron density and the largest occurrence of GPS signal loss. From a longitudinal perspective, the higher depletion amplitude is always witnessed in spatial bins with higher background electron density. At most longitudes, the occurrence rate of postmidnight EPDs is reduced compared to premidnight ones; while more postmidnight EPDs are observed at African longitudes. CHAMP observations confirm this point regardless of high or low solar activity condition. Further by comparing with previous studies and the plasma vertical drift velocity from ROCSAT-1, we suggest that while the F region vertical plasma drift plays a key role in dominating the occurrence of EPDs during premidnight hours, the postmidnight EPDs are the combined results from the continuing of former EPDs and newborn EPDs, especially during June solstice. And these newborn EPDs during postmidnight hours seem to be less related to the plasma vertical drift.}, language = {en} } @article{LaeppleMuenchCasadoetal.2018, author = {Laepple, Thomas and M{\"u}nch, Thomas and Casado, Mathieu and Hoerhold, Maria and Landais, Amaelle and Kipfstuhl, Sepp}, title = {On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {12}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, number = {1}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1994-0416}, doi = {10.5194/tc-12-169-2018}, pages = {169 -- 187}, year = {2018}, abstract = {Stable isotope ratios delta O-18 and delta D in polar ice provide a wealth of information about past climate evolution. Snow-pit studies allow us to relate observed weather and climate conditions to the measured isotope variations in the snow. They therefore offer the possibility to test our understanding of how isotope signals are formed and stored in firn and ice. As delta O-18 and delta D in the snowfall are strongly correlated to air temperature, isotopes in the near-surface snow are thought to record the seasonal cycle at a given site. Accordingly, the number of seasonal cycles observed over a given depth should depend on the accumulation rate of snow. However, snow-pit studies from different accumulation conditions in East Antarctica reported similar isotopic variability and comparable apparent cycles in the delta O-18 and delta D profiles with typical wavelengths of similar to 20 cm. These observations are unexpected as the accumulation rates strongly differ between the sites, ranging from 20 to 80mmw.e.yr(-1) (similar to 6-21 cm of snow per year). Various mechanisms have been proposed to explain the isotopic variations individually at each site; however, none of these are consistent with the similarity of the different profiles independent of the local accumulation conditions. Here, we systematically analyse the properties and origins of delta O-18 and delta D variations in high-resolution firn profiles from eight East Antarctic sites. First, we confirm the suggested cycle length (mean distance between peaks) of similar to 20 cm by counting the isotopic maxima. Spectral analysis further shows a strong similarity between the sites but indicates no dominant periodic features. Furthermore, the appar-ent cycle length increases with depth for most East Antarctic sites, which is inconsistent with burial and compression of a regular seasonal cycle. We show that these results can be explained by isotopic diffusion acting on a noise-dominated isotope signal. The firn diffusion length is rather stable across the Antarctic Plateau and thus leads to similar power spectral densities of the isotopic variations. This in turn implies a similar distance between isotopic maxima in the firn profiles. Our results explain a large set of observations discussed in the literature, providing a simple explanation for the interpretation of apparent cycles in shallow isotope records, without invoking complex mechanisms. Finally, the results underline previous suggestions that isotope signals in single ice cores from low-accumulation regions have a small signal-to-noise ratio and thus likely do not allow the reconstruction of interannual to decadal climate variations.}, language = {en} } @article{HermanBraunDealetal.2018, author = {Herman, Frederic and Braun, Jean and Deal, Eric and Prasicek, Gunther}, title = {The response time of glacial erosion}, series = {Journal of geophysical research : Earth surface}, volume = {123}, journal = {Journal of geophysical research : Earth surface}, number = {4}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9003}, doi = {10.1002/2017JF004586}, pages = {801 -- 817}, year = {2018}, abstract = {There has been recent progress in the understanding of the evolution of Quaternary climate. Simultaneously, there have been improvements in the understanding of glacial erosion processes, with better parameter constraints. Despite this, there remains much debate about whether or not the observed cooling over the Quaternary has driven an increase in glacial erosion rates. Most studies agree that the erosional response to climate change must be transient; therefore, the time scale of the climatic change and the response time of glacial erosion must be accounted for. Here we analyze the equations governing glacial erosion in a steadily uplifting landscape with variable climatic forcing and derive expressions for two fundamental response time scales. The first time scale describes the response of the glacier and the second one the glacial erosion response. We find that glaciers have characteristic time scales of the order of 10 to 10,000 years, while the characteristic time scale for glacial erosion is of the order of a few tens of thousands to a few million years. We then use a numerical model to validate the approximations made to derive the analytical solutions. The solutions show that short period forcing is dampened by the glacier response time, and long period forcing (>1 Myr) may be dampened by erosional response of glaciers when the rock uplift rates are high. In most tectonic and climatic conditions, we expect to see the strongest response of glacial erosion to periodic climatic forcing corresponding to Plio-Pleistocene climatic cycles. Finally, we use the numerical model to predict the response of glacial systems to the observed climatic forcing of the Quaternary, including, but not limited to, the Milankovich periods and the long-term secular cooling trend. We conclude that an increase of glacial erosion in response to Quaternary cooling is physically plausible, and we show that the magnitude of the increase depends on rock uplift and ice accumulation rates.}, language = {en} } @article{FerreroGodardPalmerietal.2018, author = {Ferrero, Silvio and Godard, Gaston and Palmeri, Rosaria and Wunder, Bernd and Cesare, Bernardo}, title = {Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica}, series = {American mineralogist : an international journal of earth and planetary materials}, volume = {103}, journal = {American mineralogist : an international journal of earth and planetary materials}, number = {4}, publisher = {Mineralogical Society of America}, address = {Chantilly}, issn = {0003-004X}, doi = {10.2138/am-2018-6214}, pages = {610 -- 622}, year = {2018}, abstract = {In the Pan-African belt of the Dronning Maud Land, Antarctica, crystallized melt inclusions (nanogranitoids) occur in garnet from ultramafic granulites. The granulites contain the peak assemblage pargasite+garnet+clinopyroxene with rare relict orthopyroxene and biotite, and retrograde symplectites at contacts between garnet and amphibole. Garnet contains two generations of melt inclusions. Type 1 inclusions, interpreted as primary, are isolated, < 10 mu m in size, and generally have negative crystal shapes. They contain kokchetavite, kumdykolite, and phlogopite, with quartz and zoisite as minor phases, and undevitrified glass was identified in one inclusion. Type 2 inclusions are < 30 mu m in size, secondary, and contain amphibole, feldspars, and zoisite. Type 2 inclusions appear to be the crystallization products of a melt that coexisted with an immiscible CO2-rich fluid. The nanogranitoids were re-homogenized after heating in a piston-cylinder in a series of four experiments to investigate their composition. The conditions ranged between 900 and 950 degrees C at 1.5-2.4 GPa. Type 1 inclusions are trachytic and ultrapotassic, whereas type 2 melts are dacitic to rhyolitic. Thermodynamic modeling of the ultramafic composition in the MnNCKFMASHTO system shows that anatexis occurred at the end of the prograde P-T path, between the solidus (at ca. 860 degrees C-1.4 GPa) and the peak conditions (at ca. 960 degrees C-1.7 GPa). The model melt composition is felsic and similar to that of type 1 inclusions, particularly when the melting degree is low (< 1 mol\%), close to the solidus. However the modeling fails to reproduce the highly potassic signature of the melt and its low H2O content. The combination of petrology, melt inclusion study, and thermodynamic modeling supports the interpretation that melt was produced by anatexis of the ultramafic boudins near peak P-T conditions, and that type 1 inclusions contain the anatectic melt that was present during garnet growth. The felsic, ultrapotassic composition of the primary anatectic melts is compatible with low melting degrees in the presence of biotite and amphibole as reactants.}, language = {en} } @article{TianCaoDallmeyeretal.2018, author = {Tian, Fang and Cao, Xianyong and Dallmeyer, Anne and Lohmann, Gerrit and Zhang, Xu and Ni, Jian and Andreev, Andrei and Anderson, Patricia M. and Lozhkin, Anatoly V. and Bezrukova, Elena and Rudaya, Natalia and Xu, Qinghai and Herzschuh, Ulrike}, title = {Biome changes and their inferred climatic drivers in northern and eastern continental Asia at selected times since 40 cal ka BP}, series = {Vegetation History and Archaeobotany}, volume = {27}, journal = {Vegetation History and Archaeobotany}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0939-6314}, doi = {10.1007/s00334-017-0653-8}, pages = {365 -- 379}, year = {2018}, abstract = {Recent global warming is pronounced in high-latitude regions (e.g. northern Asia), and will cause the vegetation to change. Future vegetation trends (e.g. the "arctic greening") will feed back into atmospheric circulation and the global climate system. Understanding the nature and causes of past vegetation changes is important for predicting the composition and distribution of future vegetation communities. Fossil pollen records from 468 sites in northern and eastern Asia were biomised at selected times between 40 cal ka bp and today. Biomes were also simulated using a climate-driven biome model and results from the two approaches compared in order to help understand the mechanisms behind the observed vegetation changes. The consistent biome results inferred by both approaches reveal that long-term and broad-scale vegetation patterns reflect global- to hemispheric-scale climate changes. Forest biomes increase around the beginning of the late deglaciation, become more widespread during the early and middle Holocene, and decrease in the late Holocene in fringe areas of the Asian Summer Monsoon. At the southern and southwestern margins of the taiga, forest increases in the early Holocene and shows notable species succession, which may have been caused by winter warming at ca. 7 cal ka bp. At the northeastern taiga margin (central Yakutia and northeastern Siberia), shrub expansion during the last deglaciation appears to prevent the permafrost from thawing and hinders the northward expansion of evergreen needle-leaved species until ca. 7 cal ka bp. The vegetation-climate disequilibrium during the early Holocene in the taiga-tundra transition zone suggests that projected climate warming will not cause a northward expansion of evergreen needle-leaved species.}, language = {en} } @article{GoslingJulierAduBreduetal.2018, author = {Gosling, William D. and Julier, Adele C. M. and Adu-Bredu, Stephen and Djagbletey, Gloria D. and Fraser, Wesley T. and Jardine, Phillip E. and Lomax, Barry H. and Malhi, Yadvinder and Manu, Emmanuel A. and Mayle, Francis E. and Moore, Sam}, title = {Pollen-vegetation richness and diversity relationships in the tropics}, series = {Vegetation History and Archaeobotany}, volume = {27}, journal = {Vegetation History and Archaeobotany}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0939-6314}, doi = {10.1007/s00334-017-0642-y}, pages = {411 -- 418}, year = {2018}, abstract = {Tracking changes in biodiversity through time requires an understanding of the relationship between modern diversity and how this diversity is preserved in the fossil record. Fossil pollen is one way in which past vegetation diversity can be reconstructed. However, there is limited understanding of modern pollen-vegetation diversity relationships from biodiverse tropical ecosystems. Here, pollen (palynological) richness and diversity (Hill N (1)) are compared with vegetation richness and diversity from forest and savannah ecosystems in the New World and Old World tropics (Neotropics and Palaeotropics). Modern pollen data were obtained from artificial pollen traps deployed in 1-ha vegetation study plots from which vegetation inventories had been completed in Bolivia and Ghana. Pollen counts were obtained from 15 to 22 traps per plot, and aggregated pollen sums for each plot were > 2,500. The palynological richness/diversity values from the Neotropics were moist evergreen forest = 86/6.8, semi-deciduous dry forest = 111/21.9, wooded savannah = 138/31.5, and from the Palaeotropics wet evergreen forest = 144/28.3, semi-deciduous moist forest = 104/4.4, forest-savannah transition = 121/14.1; the corresponding vegetation richness/diversity was 100/36.7, 80/38.7 and 71/39.4 (Neotropics), and 101/54.8, 87/45.5 and 71/34.5 (Palaeotropics). No consistent relationship was found between palynological richness/diversity, and plot vegetation richness/diversity, due to the differential influence of other factors such as landscape diversity, pollination strategy, and pollen source area. Palynological richness exceeded vegetation richness, while pollen diversity was lower than vegetation diversity. The relatively high global diversity of tropical vegetation was found to be reflected in the pollen rain.}, language = {en} } @article{RehfeldMuenchHoetal.2018, author = {Rehfeld, Kira and M{\"u}nch, Thomas and Ho, Sze Ling and Laepple, Thomas}, title = {Global patterns of declining temperature variability from the Last Glacial Maximum to the Holocene}, series = {Nature : the international weekly journal of science}, volume = {554}, journal = {Nature : the international weekly journal of science}, number = {7692}, publisher = {Nature Publ. Group}, address = {London}, issn = {0028-0836}, doi = {10.1038/nature25454}, pages = {356 -- 359}, year = {2018}, abstract = {Changes in climate variability are as important for society to address as are changes in mean climate(1). Contrasting temperature variability during the Last Glacial Maximum and the Holocene can provide insights into the relationship between the mean state of the climate and its variability(2,3). However, although glacial-interglacial changes in variability have been quantified for Greenland(2), a global view remains elusive. Here we use a network of marine and terrestrial temperature proxies to show that temperature variability decreased globally by a factor of four as the climate warmed by 3-8 degrees Celsius from the Last Glacial Maximum (around 21,000 years ago) to the Holocene epoch (the past 11,500 years). This decrease had a clear zonal pattern, with little change in the tropics (by a factor of only 1.6-2.8) and greater change in the mid-latitudes of both hemispheres (by a factor of 3.3-14). By contrast, Greenland ice-core records show a reduction in temperature variability by a factor of 73, suggesting influences beyond local temperature or a decoupling of atmospheric and global surface temperature variability for Greenland. The overall pattern of reduced variability can be explained by changes in the meridional temperature gradient, a mechanism that points to further decreases in temperature variability in a warmer future.}, language = {en} } @article{ZwiebackKokeljGuentheretal.2018, author = {Zwieback, Simon and Kokelj, Steven V. and G{\"u}nther, Frank and Boike, Julia and Grosse, Guido and Hajnsek, Irena}, title = {Sub-seasonal thaw slump mass wasting is not consistently energy limited at the landscape scale}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {12}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, number = {2}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1994-0416}, doi = {10.5194/tc-12-549-2018}, pages = {549 -- 564}, year = {2018}, abstract = {Predicting future thaw slump activity requires a sound understanding of the atmospheric drivers and geomorphic controls on mass wasting across a range of timescales. On sub-seasonal timescales, sparse measurements indicate that mass wasting at active slumps is often limited by the energy available for melting ground ice, but other factors such as rainfall or the formation of an insulating veneer may also be relevant. To study the sub-seasonal drivers, we derive topographic changes from single-pass radar interferometric data acquired by the TanDEM-X satellites. The estimated elevation changes at 12m resolution complement the commonly observed planimetric retreat rates by providing information on volume losses. Their high vertical precision (around 30 cm), frequent observations (11 days) and large coverage (5000 km(2)) allow us to track mass wasting as drivers such as the available energy change during the summer of 2015 in two study regions. We find that thaw slumps in the Tuktoyaktuk coastlands, Canada, are not energy limited in June, as they undergo limited mass wasting (height loss of around 0 cm day 1) despite the ample available energy, suggesting the widespread presence of early season insulating snow or debris veneer. Later in summer, height losses generally increase (around 3 cm day 1), but they do so in distinct ways. For many slumps, mass wasting tracks the available energy, a temporal pattern that is also observed at coastal yedoma cliffs on the Bykovsky Peninsula, Russia. However, the other two common temporal trajectories are asynchronous with the available energy, as they track strong precipitation events or show a sudden speed-up in late August respectively. The observed temporal patterns are poorly related to slump characteristics like the headwall height. The contrasting temporal behaviour of nearby thaw slumps highlights the importance of complex local and temporally varying controls on mass wasting.}, language = {en} } @article{OmraniMoazzenOberhaensli2018, author = {Omrani, Hadi and Moazzen, Mohssen and Oberh{\"a}nsli, Roland}, title = {Geodynamic evolution of the Sabzevar zone, northern central Iranian micro-continent}, series = {Mineralogy and petrology}, volume = {112}, journal = {Mineralogy and petrology}, number = {1}, publisher = {Springer}, address = {Wien}, issn = {0930-0708}, doi = {10.1007/s00710-017-0505-3}, pages = {65 -- 83}, year = {2018}, abstract = {The Northern Central Iranian Micro-continent (CIM) represents Neotethys-related oceanic crust remnants, emplaced due to convergence between CIM and Eurasia plates during Eocene. Mafic and ultramafic units are exposed along the northern part of the CIM in the Sabzevar area. The geology and field relation of Sabzevar ophiolite indicate northward subduction of the Sabzevar basin. The average whole rock chemistry of mafic (gabbros) and ultramafic samples (lherzolite, harzburgite and dunite) is characterized by a range of MgO of 11.16-31.88, CaO 5.22-11.53 and Al2O3 2.77-14.57, respectively. Low LREE/HREE ratio of ultramafic samples is accompanied by enrichment of large ion lithophile elements (LILE) such as Sr, Pb and K. Mafic samples show two distinct groups with low and high LREE/HREE ratios. The spider diagram of mafic samples indicates enrichment in Sr, Pb and K and depletion in REE. Petrological and geochemical evidence and field relations show that the mafic rocks formed in a supra-subduction zone setting. Petrological studies reveal the role of fractional crystallization and assimilation effect by released fluids during subduction related generation of the Sabzevar mafic rocks. We suggest that the studied mafic rocks likely represent the basement of an initial island arc, which was generated in a supra-subduction zone setting within the Neotethys branch of the Sabzevar Ocean at the north of CIM. Copper, gold and chromite mineralizations are studied in relation to island arc setting and supra-subduction environment. Similarities in lithology, ophiolite age and mineralization between Sabzevar ophiolite and Bardaskan-Torbat Heydariyeh ophiolites testify for their separation due to rotation (or faulting) of the Central Iranian Micro-continent.}, language = {en} } @article{LaraNitzeGrosseetal.2018, author = {Lara, Mark J. and Nitze, Ingmar and Grosse, Guido and Martin, Philip and McGuire, A. David}, title = {Reduced arctic tundra productivity linked with landform and climate change interactions}, series = {Scientific reports}, volume = {8}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-018-20692-8}, pages = {10}, year = {2018}, abstract = {Arctic tundra ecosystems have experienced unprecedented change associated with climate warming over recent decades. Across the Pan-Arctic, vegetation productivity and surface greenness have trended positively over the period of satellite observation. However, since 2011 these trends have slowed considerably, showing signs of browning in many regions. It is unclear what factors are driving this change and which regions/landforms will be most sensitive to future browning. Here we provide evidence linking decadal patterns in arctic greening and browning with regional climate change and local permafrost-driven landscape heterogeneity. We analyzed the spatial variability of decadal-scale trends in surface greenness across the Arctic Coastal Plain of northern Alaska (similar to 60,000 km(2)) using the Landsat archive (1999-2014), in combination with novel 30 m classifications of polygonal tundra and regional watersheds, finding landscape heterogeneity and regional climate change to be the most important factors controlling historical greenness trends. Browning was linked to increased temperature and precipitation, with the exception of young landforms (developed following lake drainage), which will likely continue to green. Spatiotemporal model forecasting suggests carbon uptake potential to be reduced in response to warmer and/or wetter climatic conditions, potentially increasing the net loss of carbon to the atmosphere, at a greater degree than previously expected.}, language = {en} }