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Die genauen Einsatzzeiten seismischer P-Phasen von Erdbeben werden in SeisComP3 und anderen Auswerteprogrammen standardmäßig und in Echtzeit automatisch bestimmt. S-Phasen stellen dagegen eine weit größere Herausforderung dar. Nur mit genauen Picks der P- bzw. S-Phasen können die Erdbebenlokationen korrekt und stabil bestimmt werden. Darum besteht erhebliches Interesse, diese mit hoher Genauigkeit zu bestimmen. Das Ziel der vorliegenden Bachelorarbeit war es, vier verschiedene, bereits vorhandene S-Phasenpicker auf ausgewählte Parameter optimal zu konfigurieren, auf Testdaten anzuwenden und deren Leistungsfähigkeit objektiv zu bewerten. Dazu wurden ein S-Picker (S-L2) aus dem OpenSource SeisComp3-Programmpaket, zwei S-Picker (S-AIC, S-AIC-V) als kommerzielles Modul der Firma gempa GmbH für SeisComP3 und ein S-Picker (Frequenzband) aus dem OpenSource PhasePaPy-Paket ausgewählt. Die Bewertung erfolgte durch Vergleich automatischer Picks mit manuell bestimmten Einsatzzeiten. Alle vier Picker wurden separat konfiguriert und auf drei verschiedene Datensätze von Erdbeben in N-Chile und im Vogtland, Deutschland, angewandt. Dazu wurden regional bzw. lokal typische Erdbeben zufällig ausgewählt und die P- und S-Phasen manuell bestimmt. Mit den zu testenden S-Pickeralgorithmen wurden dieselben Daten durchsucht und die Picks automatisch bestimmt. Die Konfigurationen der Picker wurden gleichzeitig automatisch und objektiv durch iterative Anpassung optimiert. Ein neu erstelltes Bewertungssystem vergleicht die manuellen und die automatisch gefundenen S-Picks anhand von definierten Qualitätsfaktoren. Die Qualitätsfaktoren sind: der Mittelwert und die Standardabweichung der zeitlichen Differenzen zwischen den S-Picks, die Anzahl an übereinstimmenden S-Picks, die Prozentangaben über mögliche S-Picks und die benötigt Rechenzeit. Die objektive Bewertung erfolgte anhand eines Scores. Der Scorewert ergibt sich aus der gewichteten Summe folgender normierter Qualitätsfaktoren: Standardabweichung (20%), Mittelwert (20%) und Prozentangabe über mögliche S-Picks (60%). Konfigurationen mit hohem Score werden bevorzugt. Die bevorzugten Konfigurationen der verschiedenen Picker wurden miteinander verglichen, um den am besten geeigneten S-Pickeralgorithmus zu bestimmen. Allgemein zeigt sich, dass der S-AIC Picker für jeden der drei Datensätze die höchsten Scores und damit die besten Ergebnisse liefert. Dabei wurde für jeden Datensatz ein andere Konfiguration der Parameter des S-AIC Pickers als die am besten geeignete bezeichnet. Daher ist für jede Erdbebenregion eine andere Konfigurationen erforderlich, um optimale Ergebnisse mit diesem S-Picker zu bekommen.
The formation of the Pamir is a key component of the India-Asia collision with major implications for lithospheric processes, plateau formation, land-sea configurations and associated climate changes. Although the formation of the Pamir is traditionally linked to Cenozoic processes associated with the India-Asia collision, the contribution of the Mesozoic tectonic evolution remains poorly understood. The Pamir was formed by the suturing of Gondwanan terranes to the south margin of Eurasia, however, the timing and tectonic mechanisms associated with this Mesozoic accretion remain poorly constrained. These processes are recorded by several igneous belts within these terranes, which are not well studied. Within the Southern Pamir, the Albian-Turonian volcanic rocks and comagmatic plutons of the Kyzylrabat Igneous Complex (KIC) provide an important and still unconstrained record of the Pamir evolution. Here we provide the age, origin and the geodynamic setting of the KIC volcanics by studying their petrology, zircon U-Pb geochronology, geochemistry and isotope composition.17 samples from the KIC volcanics yield U-Pb ages spanning from 92 to 110 Ma. The volcanics are intermediate to acidic in composition (SiO2 = 56-69 wt%) and exhibit high-K calc-alkaline and shoshonitic affinity (K2O/Na2O = 12.2 wt%). They show enrichment in LILE and LREE and depletion in HFSE and HREE with negative Ta, Ti and Nb anomalies, suggesting an arc-related tectonic setting for their formation. Low sNd(t) values (from 9.1 to 4.7), relatively high Sr-87/Sr-86(i) ratios (0.7069-0.7096) and broad range of zircon stif values (from 22.6 to 1.5) suggest a mixture of different magma sources. These features suggest that volcanics were derived by crustal under- or intraplating of an enriched subduction-related mantle shoshonitic magmas, by heating and partial melting of the lower crust, and by mixing of both magma components. Our results further imply that the KIC volcanics represent a shoshonitic suite typical of an evolution from active continental arc to post-collisional setting with a steepening of the Benioff zone and thickening of the crust toward the back-arc. This setting is best explained by the subduction- collision transition along the Shyok suture due to accretion of the Kohistan island arc to the Karakoram. This suggests that a significant part of the crustal shortening and thickening accommodated in the Pamir occurred in the Mesozoic before the India-Asia collision with implications for regional tectonic models. This further suggests the Pamir was already a major topographic feature with potentially important paleoclimate forcing such as the monsoonal circulation. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
The northern edge of the western central Tien Shan range is bounded by the Issyk-Ata fault situated south of Bishkek, the capital of Kyrgyzstan. Contraction in this thick-skinned orogen occurs with low-strain accumulation and long earthquake recurrence intervals. In the nineteenth to twentieth centuries, a sequence of large earthquakes with magnitudes between 6.9 and 8 affected the northern Tien Shan but left nearly the entire extent of the Issyk-Ata fault unruptured. Here, the only known historic earthquake ruptured in A.D. 1885 (M6.9) along the western end of the Issyk-Ata fault. Because earthquakes in low-strain regions often tend to cluster in time and may promote failure along nearby structures, the earthquake history of the northern Tien Shan represents an exceptional structural setting for studying fault behavior affected by an intraplate earthquake sequence. We present a paleoseismological study from one site (Belek) along the Issyk-Ata fault located east of the A.D. 1885 epicentral area. Our analysis combines a range of tools, including photogrammetry, differential Global Positioning System, 3D visualization, and age modeling with different dating methods (infrared stimulated luminescence, radiocarbon, U-series) to improve the reliability of an event chronology for the trench stratigraphy and fault geometry. We were able to distinguish three different surfacerupturing paleoearthquakes; these affected the area before 10.5 +/- 1.1 cal ka B.P., at similar to 5.6 +/- 1.0 cal ka B.P., and at similar to 630 +/- 100 cal B.P., respectively. Associated paleomagnitudes for the last two earthquakes range between M6.7 and 7.4, with a cumulative slip rate of 0.7 +/- 0.32 mm/yr. We did not find evidence for the A.D. 1885 event at Belek. Our study yielded two main overall results: first, it extends the regional historic and paleoseismic record; second, the documented rupture events along the Issyk-Ata fault suggest that this fault was not affected in its entirety; instead, these events indicate segmented rupture behavior.
This article presents a review of the current data on the level of paleolimnological knowledge about lakes in the Russian part of the northern Eurasia. The results of investigation of the northwestern European part of Russia as the best paleolimnologically studied sector of the Russian north is presented in detail. The conditions of lacustrine sedimentation at the boundary between the Late Pleistocene and Holocene and the role of different external factors in formation of their chemical composition, including active volcanic activity and possible large meteorite impacts, are also discussed. The results of major paleoclimatic and paleoecological reconstructions in northern Siberia are presented. Particular attention is given to the databases of abiotic and biotic parameters of lake ecosystems as an important basis for quantitative reconstructions of climatic and ecological changes in the Late Pleistocene and Holocene. Keywords: paleolimnology, lakes, bottom sediments, northern.
The purpose of our study is to reconstruct the climatic and environmental changes that took place over the Holocene in Northwest Russia. The results of the palaeobiological analysis of cladoceran community of Lake Medvedevskoe (Karelian Isthmus, located between the Gulf of Finland of the Baltic Sea and Lake Ladoga, Northwest Russia) have been discussed. In the sediments of Lake Medvedevskoe, we have identified 38 cladoceran taxa that belong to 7 families: Bosminidae, Holopedidae, Chydoridae, Daphnidae, Polyphemidae, Macrotricidae, and Sididae. It has been revealed that Bosmina (Eubosmina) longispina and Alonella nana are the most common for subfossil Cladocera community of the lake. Palearctic and Holarctic species are dominant. Both pelagic and littoral taxa are well represented in the lake. The down-core changes in cladoceran community allowed to identify five statistically significant zones. It has been discovered that the taxonomic richness of biological communities is low at the bottom of the core with the dominance of typical northern species and increases towards the sediment surface alongside with the rise of organic content in sediments. Based on the shifts in the taxonomic composition of cladoceran community, we have concluded upon the trophic status of the lake and climate changes. The obtained data have been compared with the results of the chironomid analysis that was performed earlier.
Chemostratigraphic studies on lacustrine sedimentary sequences provide essential insights on past cyclic climatic events, on their repetition and prediction through time. Diagenetic overprint of primary features often hinders the use of such studies for palaeoenvironmental reconstruction. Here the potential of integrated geochemical and petrographic methods is evaluated to record freshwater to saline oscillations within the ancient marginal lacustrine carbonates of the Miocene Ries Crater Lake (Germany). This area is critical because it represents the transition from shoreline to proximal domains of a hydrologically closed system, affected by recurrent emergent events, representing the boundaries of successive sedimentary cycles. Chemostratigraphy targets shifts related to subaerial exposure and/or climatic fluctuations. Methods combine facies changes with C-13-O-18 chemostratigraphy from matrix carbonates across five closely spaced, temporally equivalent stratigraphic sections. Isotope composition of ostracod shells, gastropods and cements is provided for comparison. Cathodoluminescence and back-scatter electron microscopy were performed to discriminate primary (syn-)depositional, from secondary diagenetic features. Meteoric diagenesis is expressed by substantial early dissolution and dark blue luminescent sparry cements carrying negative C-13 and O-18. Sedimentary cycles are not correlated by isotope chemostratigraphy. Both matrix C-13 and O-18 range from ca -75 to +40 parts per thousand and show clear positive covariance (R=097) whose nature differs from that of previous basin-oriented studies on the lake: negative values are here unconnected to original freshwater lacustrine conditions but reflect extensive meteoric diagenesis, while positive values probably represent primary saline lake water chemistry. Noisy geochemical curves relate to heterogeneities in (primary) porosity, resulting in selective carbonate diagenesis. This study exemplifies that ancient lacustrine carbonates, despite extensive meteoric weathering, are able to retain key information for both palaeoenvironmental reconstruction and the understanding of diagenetic processes in relation to those primary conditions. Also, it emphasizes the limitation of chemostratigraphy in fossil carbonates, and specifically in settings that are sensitive for the preservation of primary environmental signals, such as lake margins prone to meteoric diagenesis.
The Bajgan Complex, one of the basement constituents of the arc massif in Iranian Makran forms a rugged, deeply incised terrain. The complex consists of pelitic schists with minor psammitic and basic schists, calc silicate rocks, amphibolites, marbles, metavolcanosediments, mafic and felsic intrusives as well as ultramafic rocks. Metapelitic rocks show an amphibolite facies regional metamorphism and contain garnet, biotite, white mica, quartz, albite ± rutile ± apatite. Thermobarometry of garnet schist yields pressure of more than 9 kbar and temperatures between 560 and 675 °C. The geothermal gradient obtained for the peak of regional metamorphism is 19 °C/km, corresponding to a depth of ca. 31 km. Replacement of garnet by chlorite and epidote suggest greenschist facies metamorphism due to a decrease in temperature and pressure through exhumation and retrograde metamorphism (370–450 °C and 3–6 kbar). The metapelitic rocks followed a ‘clockwise’ P–T path during metamorphism, consistent with thermal decline following tectonic thickening. The formation of medium-pressure metamorphic rocks is related to presence of active subduction of the Neotethys Oceanic lithosphere beneath Eurasia in the Makran.
This study analyzes the discharge variability of small to medium drainage basins (10(2)-10(4) km(2)) in the southern Central Andes of NW Argentina. The Hilbert-Huang Transform (HHT) was applied to evaluate non-stationary oscillatory modes of variability and trends, based on four time series of monthly normalized discharge anomaly between 1940 and 2015. Statistically significant trends reveal increasing discharge during the past decades and document an intensification of the hydrological cycle during this period. An Ensemble Empirical Mode Decomposition (EEMD) analysis revealed that discharge variability in this region can be best described by five quasi-periodic statistically significant oscillatory modes, with mean periods varying from 1 to 20 y. Moreover, we show that discharge variability is most likely linked to the phases of the Pacific Decadal Oscillation (PDO) at multi-decadal timescales (similar to 20 y) and, to a lesser degree, to the Tropical South Atlantic SST anomaly (TSA) variability at shorter timescales (similar to 2-5 y). Previous studies highlighted a rapid increase in discharge in the southern Central Andes during the 1970s, inferred to have been associated with the global 1976-77 climate shift. Our results suggest that the rapid discharge increase in the NW Argentine Andes coincides with the periodic enhancement of discharge, which is mainly linked to a negative to positive transition of the PDO phase and TSA variability associated with a long-term increasing trend. We therefore suggest that variations in discharge in this region are largely driven by both natural variability and the effects of global climate change. We furthermore posit that the links between atmospheric and hydrologic processes result from a combination of forcings that operate on different spatiotemporal scales. (C) 2017 Elsevier B.V. All rights reserved.
The paleoclimate during the Early Eocene in Maritime Antarctica is characterized by cool conditions without a pronounced dry season. Soils formed on volcanic material under such climate conditions in modern analogue environments are usually Andosols rich in nanocrystalline minerals without pedogenic smectite. The paleosols formed on volcanic material on King Georges Island are covered by basalts, dated by 6 new 40Ar/39Ar datings to 51-48 Ma, and are rich in smectite. A pedogenic origin of the smectites would suggest a semi-arid rather than a wet non-seasonal humid paleoclimate. To investigate the origin of the smectites in these paleosols we used X-ray diffraction and microscopic techniques. Minor mineralogical changes between the volcanic parent material and the paleosols and a homogenous distribution of smectites throughout the paleosol horizons indicate that these smectites were mainly inherited from the pyroclastic parent material, which was altered prior to surficial weathering. Nevertheless, the mineralogical properties, such as degree of crystallinity and octahedral site occupancy, of these smectites were modified during the ancient soil formation. Our findings highlight that trioctahedral smectites were a product of deuteric alteration of pyroclastic rocks and were progressively transformed to dioctahedral smectites during weathering in a soil environment on King George Island.
On trend detection
(2017)
A main obstacle to trend detection in time series occurs when they are autocorrelated. By reducing the effective sample size of a series, autocorrelation leads to decreased trend significance. Numerous recipes attempt to mitigate the effect of autocorrelation, either by adjusting for the reduced effective sample size or by removing the autocorrelated components of a series. This short note deals with the latter, also called prewhitening (PW). It is known that removal of autocorrelation also removes part of the trend, which may affect the signal-to-noise ratio. Two popular methods have dealt with this problem, the trend-free prewhitening (TFPW) and the iterative prewhitening. Although it is generally accepted that both methods reduce the adverse effects of PW on the trend magnitude, corresponding effects on statistical significance have not been clearly stated for TFPW. Using a Monte Carlo approach, it is demonstrated that both methods entail quite different Type-I error rates. The iterative prewhitening produces rates that are generally close to the nominal significance level. The TFPW, however, shows very high Type-I error rates with increasing autocorrelation. The corresponding rate of false trend detections is unacceptable for applications, so that published trends based on TFPW need to be reassessed.
Magnetic and electric field observations from the European Space Agency Swarm mission are used to report the direction of electromagnetic energy flux associated with equatorial plasma depletions. Contrary to expectations, the observations suggest a general interhemispheric Poynting flux rather than concurrent flows at both hemispheres toward or away from the equator. Of high interest is a particular behavior noticed over the region with the largest variation in the magnetic declination. This is a Poynting flux flowing mainly into the southern magnetic hemisphere about between 60 degrees W and 30 degrees E and into the northern magnetic hemisphere between 110 degrees W and 60 degrees W. The abrupt change in the flow direction at 60 degrees W is suggested to be caused by an asymmetry between the hemispheres on the ionospheric conductivity, likely due to the influence of thermospheric winds and the presence of the South Atlantic Anomaly.
To what extent cities can be made sustainable under the mega-trends of urbanization and climate change remains a matter of unresolved scientific debate. Our inability in answering this question lies partly in the deficient knowledge regarding pivotal humanenvironment interactions. Regarded as the most well documented anthropogenic climate modification, the urban heat island (UHI) effect – the warmth of urban areas relative to the rural hinterland – has raised great public health concerns globally. Worse still, heat waves are being observed and are projected to increase in both frequency and intensity, which further impairs the well-being of urban dwellers. Albeit with a substantial increase in the number of publications on UHI in the recent decades, the diverse urban-rural definitions applied in previous studies have remarkably hampered the general comparability of results achieved. In addition, few studies have attempted to synergize the land use data and thermal remote sensing to systematically assess UHI and its contributing factors.
Given these research gaps, this work presents a general framework to systematically quantify the UHI effect based on an automated algorithm, whereby cities are defined as clusters of maximum spatial continuity on the basis of land use data, with their rural hinterland being defined analogously. By combining land use data with spatially explicit surface skin temperatures from satellites, the surface UHI intensity can be calculated in a consistent and robust manner. This facilitates monitoring, benchmarking, and categorizing UHI intensities for cities across scales. In light of this innovation, the relationship between city size and UHI intensity has been investigated, as well as the contributions of urban form indicators to the UHI intensity.
This work delivers manifold contributions to the understanding of the UHI, which have complemented and advanced a number of previous studies. Firstly, a log-linear relationship between surface UHI intensity and city size has been confirmed among the 5,000 European cities. The relationship can be extended to a log-logistic one, when taking a wider range of small-sized cities into account. Secondly, this work reveals a complex interplay between UHI intensity and urban form. City size is found to have the strongest influence on the UHI intensity, followed by the fractality and the anisometry. However, their relative contributions to the surface UHI intensity depict a pronounced regional heterogeneity, indicating the importance of considering spatial patterns of UHI while implementing UHI adaptation measures.
Lastly, this work presents a novel seasonality of the UHI intensity for individual clusters in the form of hysteresis-like curves, implying a phase shift between the time series of UHI intensity and background temperatures. Combining satellite observation and urban boundary layer simulation, the seasonal variations of UHI are assessed from both screen and skin levels. Taking London as an example, this work ascribes the discrepancies between the seasonality observed at different levels mainly to the peculiarities of surface skin temperatures associated with the incoming solar radiation. In addition, the efforts in classifying cities according to their UHI characteristics highlight the important role of regional climates in determining the UHI.
This work serves as one of the first studies conducted to systematically and statistically scrutinize the UHI. The outcomes of this work are of particular relevance for the overall spatial planning and regulation at meso- and macro levels in order to harness the benefits of rapid urbanization, while proactively minimizing its ensuing thermal stress.
Natural and potentially hazardous events occur on the Earth’s surface every day. The most destructive of these processes must be monitored, because they may cause loss of lives, infrastructure, and natural resources, or have a negative effect on the environment. A variety of remote sensing technologies allow the recoding of data to detect these processes in the first place, partly based on the diagnostic landforms that they form. To perform this effectively, automatic methods are desirable.
Universal detection of natural hazards is challenging due to their differences in spatial impacts, timing and longevity of consequences, and the spatial resolution of remote-sensing data. Previous studies have reported that topographic metrics such as roughness, which can be captured from digital elevation data, can reveal landforms diagnostic of natural hazards, such as gullies, dunes, lava fields, landslides and snow avalanches, as these landforms tend to be more heterogeneous than the surrounding landscape. A single roughness metric is often limited in such detections; however, a more complex approach that exploits the spatial relation and the location of objects, such as object-based image analysis (OBIA), is desirable.
In this thesis, I propose a topographic roughness measure derived from an airborne laser scanning (ALS) digital terrain model (DTM) and discuss its performance in detecting landforms principally diagnostic of natural hazards. I further develop OBIA-based algorithms for the detection of snow avalanches using near-infrared (NIR) aerial images, and the size (changes) of mountain lakes using LANDSAT satellite images. I quantitatively test and document how the level of difficulty in detecting these very challenging landforms depends on the input data resolution, the derivatives that could be evaluated from images and DTMs, the size, shape and complexity of landforms, and the capabilities of obtaining the information in the data. I demonstrate that surface roughness is a promising metric for detecting different landforms in diverse environments, and that OBIA assists significantly in detecting parts of lakes and snow avalanches that may not be correctly assigned by applying only the thresholding of spectral properties of data and their derivatives.
The curvature-based surface roughness parameter allows the detection of gullies, dunes, lava fields and landslides with a user’s accuracy of 0.63, 0.21, 0.53, and 0.45, respectively. The OBIA algorithms for detecting lakes and snow avalanches obtained user’s accuracy of 0.98, and 0.78, respectively. Most of the analysed landforms constituted only a small part of the entire dataset, and therefore the user’s accuracy is the most appropriate performance measure that should be given in a such classification, because it tells how many automatically-extracted pixels in fact represent the object that one wants to classify, and its calculation does not take the second (background) class into account. One advantage of the proposed roughness parameter is that it allows the extraction of the heterogeneity of the surface without the need for data detrending. The OBIA approach is novel in that it allows the classification of lakes regardless of the physical state of their water, and also allows the separation of frozen lakes from glaciers that have very similar water indices used in purely optical remote sensing applications. The algorithm proposed for snow avalanches allows the detection of release zones, tracks, and deposition zones by verifying the snow heterogeneity based on a roughness metric evaluated from a water index, and by analysing the local relation of segments with their neighbouring objects. This algorithm contains few steps, which allows for the simultaneous classification of avalanches that occur on diverse mountain slopes and differ in size and shape.
This thesis contributes to natural hazard research as it provides automatic solutions to tracking six different landforms that are diagnostic of natural hazards over large regions. This is a step toward delineating areas susceptible to the processes producing these landforms and the improvement of hazard maps.
Underground coal gasification (UCG) has the potential to increase worldwide coal reserves by developing coal resources, currently not economically extractable by conventional mining methods. For that purpose, coal is combusted in situ to produce a high-calorific synthesis gas with different end-use options, including electricity generation as well as production of fuels and chemical feedstock. Apart from the high economic potentials, UCG may induce site‐specific environmental impacts, including ground surface subsidence and pollutant migration of UCG by-products into shallow freshwater aquifers. Sustainable and efficient UCG operation requires a thorough understanding of the coupled thermal, hydraulic and mechanical processes, occurring in the UCG reactor vicinity. The development and infrastructure costs of UCG trials are very high; therefore, numerical simulations of coupled processes in UCG are essential for the assessment of potential environmental impacts. Therefore, the aim of the present study is to assess UCG-induced permeability changes, potential hydraulic short circuit formation and non-isothermal multiphase fluid flow dynamics by means of coupled numerical simulations. Simulation results on permeability changes in the UCG reactor vicinity demonstrate that temperature-dependent thermo-mechanical parameters have to be considered in near-field assessments, only. Hence, far-field simulations do not become inaccurate, but benefit from increased computational efficiency when thermo-mechanical parameters are maintained constant. Simulations on potential hydraulic short circuit formation between single UCG reactors at regional-scale emphasize that geologic faults may induce hydraulic connections, and thus compromise efficient UCG operation. In this context, the steam jacket surrounding high-temperature UCG reactors plays a vital role in avoiding UCG by-products escaping into freshwater aquifers and in minimizing energy consumption by formation fluid evaporation. A steam jacket emerges in the close reactor vicinity due to phase transition of formation water and is a non-isothermal flow phenomenon. Considering this complex multiphase flow behavior, an innovative conceptual modeling approach, validated against field data, enables the quantification and prediction of UCG reactor water balances. The findings of this doctoral thesis provide an important basis for integration of thermo-hydro-mechanical simulations in UCG, required for the assessment and mitigation of its potential environmental impacts as well as optimization of its efficiency.
Normally in paleoseismology, the study of the tectonic slip-rate is performed in trenches on the fault scarp, or by the estimation of fault movements from the geomorphic features. In this work, we have carried out a paleoseismic analysis of the Benis Fault, located in southeast Spain, combined with a geothermal analysis inside a deep cave related to the fault (-350 m). Thus, we have estimated the last earthquake magnitude and time of occurrence from evidence of ceiling collapse and displaced carbonate blocks inside a cave, which is developed across the fault. The magnitude was obtained from the application of the empirical relationship of the fault parameters and coseismic vertical displacement, yielding a value ranging between M 5.9 and M 6.5. Moreover, we dated this paleoearthquake by the paleontological record of a "Lynx pardinus spelaea", with an age of 65 +/- 18 ka BP. Additionally, we have measured the thermal profile of the Benis Cave (-350 m of depth), from single rock point temperature measurements during 2 years. The temperature profile shows three different parts inside the cave, the shallow heterogeneous thermal zone till 50 m depth; the homogeneous thermal zone 150 m till with constant temperature and the hetero-thermal deep zone, deeper than 150 m and till the deepest zone (350 m). Furthermore, we have estimated the Vertical Geothermal Gradient, 1.85 degrees C/100 m for the deepest zone (-150; -290 m). The temperature increases with depth, showing a reverse thermal profile in comparison with normal gradients in deep caves. Finally, we have calculated the heat flux of 0.46 mWm(2). (C) 2016 Elsevier Ltd and INQUA. All rights reserved.
Flood damage can be mitigated if the parties at risk are reached by flood warnings and if they know how to react appropriately. To gain more knowledge about warning reception and emergency response of private households and companies, surveys were undertaken after the August 2002 and the June 2013 floods in Germany. Despite pronounced regional differences, the results show a clear overall picture: in 2002, early warnings did not work well; e.g. many households (27 %) and companies (45 %) stated that they had not received any flood warnings. Additionally, the preparedness of private households and companies was low in 2002, mainly due to a lack of flood experience. After the 2002 flood, many initiatives were launched and investments undertaken to improve flood risk management, including early warnings and an emergency response in Germany. In 2013, only a small share of the affected households (5 %) and companies (3 %) were not reached by any warnings. Additionally, private households and companies were better prepared. For instance, the share of companies which have an emergency plan in place has increased from 10% in 2002 to 34% in 2013. However, there is still room for improvement, which needs to be triggered mainly by effective risk and emergency communication. The challenge is to continuously maintain and advance an integrated early warning and emergency response system even without the occurrence of extreme floods.
The Cotentin Peninsula (Normandy, France) displays sequences of marine terraces and rasas, the latter being wide Late Cenozoic coastal erosion surfaces, that are typical of Western European coasts in Portugal, Spain, France and southern England. Remote sensing imagery and field mapping enabled reappraisal of the Cotentin coastal sequences. From bottom to top, the N Cotentin sequence includes four previously recognized Pleistocene marine terraces (T1 to T4) at elevations <40 m as well as four higher and older rasas (R1 to R4) reaching 200 +/- 5 m in elevation. Low-standing marine terraces are not observed in the central part of the Peninsula and a limited number of terraces are described to the south. The high-standing rasas are widespread all over the peninsula. Such strandline distributions reveal major changes during the Late Cenozoic. Progressive uplift of an irregular sea-floor led to subaerial exposure of bathymetric highs that were carved into rocky platforms, rasas and marine terraces. Eventually, five main islands coalesced and connected to the mainland to the south to form the Cotentin Peninsula. On the basis of previous dating of the last interglacial maximum terrace (i.e. Marine Isotopic Stage, MIS 5e), sequential morphostratigraphy and modelling, we have reappraised uplift rates and derived: (i) mean Upper Pleistocene (i.e. since MIS 5e similar to 122 +/- 6 ka, i.e. kilo annum) apparent uplift rates of 0.04 +/- 0.01 mm/yr, (ii) mean Middle Pleistocene eustasy-corrected uplift rates of 0.09 +/- 0.03 mm/yr, and (iii) low mean Pleistocene uplift rates of 0.01 mm/yr. Extrapolations of these slow rates combined with geological evidence implies that the formation of the sequences from the Cotentin Peninsula occurred between 3 Ma (Pliocene) and 15 Ma (Miocene), which cannot be narrowed down further without additional research. Along the coasts of Western Europe, sequences of marine terraces and rasas are widespread (169 preserve the MIS Se benchmark). In Spain, Portugal, S England and other parts of western France, the sequences morphostratigraphy is very similar to that of Cotentin. The onset of such Western European sequences occurred during the Miocene (e.g. Spain) or Pliocene (e.g. Portugal). We interpret this Neogene-Quaternary coastal uplift as a symptom of the increasing lithospheric compression that accompanies Cenozoic orogenies. (C) 2017 Elsevier B.V. All rights reserved.
Density dependence is of fundamental importance for population and range dynamics. Density-dependent reproduction of plants arises from competitive and facilitative plant-plant interactions that can be pollination independent or pollination mediated. In small and sparse populations, conspecific density dependence often turns from negative to positive and causes Allee effects. Reproduction may also increase with heterospecific density (community-level Allee effect), but the underlying mechanisms are poorly understood and the consequences for community dynamics can be complex. Allee effects have crucial consequences for the conservation of declining species, but also the dynamics of range edge populations. In invasive species, Allee effects may slow or stop range expansion. Observational studies in natural plant communities cannot distinguish whether reproduction is limited by pollination-mediated interactions among plants or by other neighbourhood effects (e.g. competition for abiotic resources). Even experimental pollen supply cannot distinguish whether variation in reproduction is caused by direct density effects or by plant traits correlated with density. Finally, it is unknown over which spatial scales pollination-mediated interactions occur. To circumvent these problems, we introduce a comprehensive experimental and analytical framework which simultaneously (1) manipulates pollen availability and quality by hand pollination and pollinator exclusion, (2) manipulates neighbourhoods by transplanting target plants, and (3) analyses the effects of con- and heterospecific neighbourhoods on reproduction with spatially explicit trait-based neighbourhood models. Synthesis. By manipulating both pollen availability and target plant locations within neighbourhoods, we can comprehensively analyse spatially explicit density dependence of plant reproduction. This experimental approach enhances our ability to understand the dynamics of sparse populations and of species geographical ranges.
Water management tools are necessary to guarantee the preservation of natural resources while ensuring optimum utilization. Linear regression models are a simple and quick solution for creating prognostic capabilities. Multivariate models show higher precision than univariate models. In the case of Waiwera, implementation of individual production rates is more accurate than applying just the total production rate. A maximum of approximately 1,075 m3/day can be pumped to ensure a water level of at least 0.5 m a.s.l. in the monitoring well. The model should be renewed annually to implement new data and current water level trends to keep the quality.
The temporal dynamics of climate processes are spread across different timescales and, as such, the study of these processes at only one selected timescale might not reveal the complete mechanisms and interactions within and between the (sub-) processes. To capture the non-linear interactions between climatic events, the method of event synchronization has found increasing attention recently. The main drawback with the present estimation of event synchronization is its restriction to analysing the time series at one reference timescale only. The study of event synchronization at multiple scales would be of great interest to comprehend the dynamics of the investigated climate processes. In this paper, the wavelet-based multi-scale event synchronization (MSES) method is proposed by combining the wavelet transform and event synchronization. Wavelets are used extensively to comprehend multi-scale processes and the dynamics of processes across various timescales. The proposed method allows the study of spatio-temporal patterns across different timescales. The method is tested on synthetic and real-world time series in order to check its replicability and applicability. The results indicate that MSES is able to capture relationships that exist between processes at different timescales.
Two nuclear explosions were carried out by the Democratic People’s Republic of North Korea in January and September 2016. Epicenters were located close to those of the 2006, 2009, and 2013 previous explosions. We perform a seismological analysis of the 2016 events combining the analysis of full waveforms at regional distances and seismic array beams at teleseismic distances. We estimate the most relevant source parameters, such as source depth, moment release, and full moment tensor (MT). The best MT solution can be decomposed into an isotropic source, directly related with the explosion and an additional deviatoric term, likely due to near‐source interactions with topographic and/or underground facilities features. We additionally perform an accurate resolution test to assess source parameters uncertainties and trade‐offs. This analysis sheds light on source parameters inconsistencies among studies on previous shallow explosive sources. The resolution of the true MT is hindered by strong source parameters trade‐offs, so that a broad range of well‐fitting MT solutions can be found, spanning from a dominant positive isotropic term to a dominant negative vertical compensated linear vector dipole. The true mechanism can be discriminated by additionally modeling first‐motion polarities at seismic arrays at teleseismic distances. A comparative assessment of the 2016 explosion with earlier nuclear tests documents similar vertical waveforms but a significant increase of amplitude for the 2016 explosions, which proves that the 9 September 2016 was the largest nuclear explosion ever performed in North Korea with a magnitude Mw 4.9 and a shallow depth of less than 2 km, although there are no proofs of a fusion explosion. Modeling transversal component waveforms suggests variable size and orientation of the double‐couple components of the 2009, 2013, and 2016 sources.
The present-day vegetation in the tropics is mainly characterized by forests worldwide except in tropical East Africa, where forests only occur as patches at the coast and in the uplands. These forest patches result from the peculiar aridity that is linked to the uplift of the region during the Late Cenozoic. The Late Cenozoic vegetation history of East Africa is of particular interest as it has set the scene for the contemporary events in mammal and hominin evolution. In this study, we investigate the conditions under which these forest patches could have been connected, and a previous continuous forest belt could have extended and fragmented. We apply a dynamic vegetation model with a set of climatic scenarios in which we systematically alter the present-day environmental conditions such that they would be more favourable for a continuous forest belt in tropical East Africa. We consider varying environmental factors, namely temperature, precipitation and atmospheric CO2 concentrations. Our results show that all of these variables play a significant role in supporting the forest biomes and a continuous forest belt could have occurred under certain combinations of these settings. With our current knowledge of the palaeoenvironmental history of East Africa, it is likely that the region hosted these conditions during the Late Cenozoic. Recent improvements on environmental hypotheses of hominin evolution highlight the role of periods of short and extreme climate variability during the Late Cenozoic specific to East Africa in driving evolution. Our results elucidate how the forest biomes of East Africa can appear and disappear under fluctuating environmental conditions and demonstrate how this climate variability might be recognized on the biosphere level.
The timing and location of the two largest earthquakes of the 21st century (Sumatra, 2004 and Tohoku 2011, events) greatly surprised the scientific community, indicating that the deformation processes that precede and follow great megathrust earthquakes remain enigmatic. During these phases before and after the earthquake a combination of multi-scale complex processes are acting simultaneously: Stresses built up by long-term tectonic motions are modified by sudden jerky deformations during earthquakes, before being restored by multiple ensuing relaxation processes.
This thesis details a cross-scale thermomechanical model developed with the aim of simulating the entire subduction process from earthquake (1 minute) to million years’ time scale, excluding only rupture propagation. The model employs elasticity, non-linear transient viscous rheology, and rate-and-state friction. It generates spontaneous earthquake sequences, and, by using an adaptive time-step algorithm, recreates the deformation process as observed naturally over single and multiple seismic cycles. The model is thoroughly tested by comparing results to those from known high- resolution solutions of generic modeling setups widely used in modeling of rupture propagation. It is demonstrated, that while not modeling rupture propagation explicitly, the modeling procedure correctly recognizes the appearance of instability (earthquake) and correctly simulates the cumulative slip at a fault during great earthquake by means of a quasi-dynamic approximation.
A set of 2D models is used to study the effects of non-linear transient rheology on the postseismic processes following great earthquakes. Our models predict that the viscosity in the mantle wedge drops by 3 to 4 orders of magnitude during a great earthquake with magnitude above 9. This drop in viscosity results in spatial scales and timings of the relaxation processes following the earthquakes that are significantly different to previous estimates. These models replicate centuries long seismic cycles exhibited by the greatest earthquakes (like the Great Chile 1960 Earthquake) and are consistent with the major features of postseismic surface displacements recorded after the Great Tohoku Earthquake.
The 2D models are also applied to study key factors controlling maximum magnitudes of earthquakes in subduction zones. Even though methods of instrumentally observing earthquakes at subduction zones have rapidly improved in recent decades, the characteristic recurrence interval of giant earthquakes (Mw>8.5) is much larger than the currently available observational record and therefore the necessary conditions for giant earthquakes are not clear. Statistical studies have recognized the importance of the slab shape and its surface roughness, state of the strain of the upper plate and thickness of sediments filling the trenches. In this thesis we attempt to explain these observations and to identify key controlling parameters. We test a set of 2D models representing great earthquake seismic cycles at known subduction zones with various known geometries, megathrust friction coefficients, and convergence rates implemented. We found that low-angle subduction (large effect) and thick sediments in the subduction channel (smaller effect) are the fundamental necessary conditions for generating giant earthquakes, while the change of subduction velocity from 10 to 3.5 cm/yr has a lower effect. Modeling results also suggest that having thick sediments in the subduction channel causes low static friction, resulting in neutral or slightly compressive deformation in the overriding plate for low-angle subduction zones. These modeling results agree well with observations for the largest earthquakes. The model predicts the largest possible earthquakes for subduction zones of given dipping angles. The predicted maximum magnitudes exactly threshold magnitudes of all known giant earthquakes of 20th and 21st centuries.
The clear limitation of most of the models developed in the thesis is their 2D nature. Development of 3D models with comparable resolution and complexity will require significant advances in numerical techniques. Nevertheless, we conducted a series of low-resolution 3D models to study the interaction between two large asperities at a subduction interface separated by an aseismic gap of varying width. The novelty of the model is that it considers behavior of the asperities during multiple seismic cycles. As expected, models show that an aseismic gap with a narrow width could not prevent rupture propagation from one asperity to another, and that rupture always crosses the entire model. When the gap becomes too wide, asperities do not interact anymore and rupture independently. However, an interesting mode of interaction was observed in the model with an intermediate width of the aseismic gap: In this model the asperities began to stably rupture in anti-phase following multiple seismic cycles. These 3D modeling results, while insightful, must be considered preliminary because of the limitations in resolution.
The technique developed in this thesis for cross-scale modeling of seismic cycles can be used to study the effects of multiple seismic cycles on the long-term deformation of the upper plate. The technique can be also extended to the case of continental transform faults and for the advanced 3D modeling of specific subduction zones. This will require further development of numerical techniques and adaptation of the existing advanced highly scalable parallel codes like LAMEM and ASPECT.
Modeling loss-propagation in the global supply network: The dynamic agent-based model acclimate
(2017)
World markets are highly interlinked and local economies extensively rely on global supply and value chains. Consequently, local production disruptions, for instance caused by extreme weather events, are likely to induce indirect losses along supply chains with potentially global repercussions. These complex loss dynamics represent a challenge for comprehensive disaster risk assessments. Here, we introduce the numerical agent-based model acclimate designed to analyze the cascading of economic losses in the global supply network. Using national sectors as agents, we apply the model to study the global propagation of losses induced by stylized disasters. We find that indirect losses can become comparable in size to direct ones, but can be efficiently mitigated by warehousing and idle capacities. Consequently, a comprehensive risk assessment cannot focus solely on first-tier suppliers, but has to take the whole supply chain into account. To render the supply network climate-proof, national adaptation policies have to be complemented by international adaptation efforts. In that regard, our model can be employed to assess reasonable leverage points and to identify dynamic bottlenecks inaccessible to static analyses. (C) 2017 Elsevier B.V. All rights reserved.
Model-Based attribution of high-resolution streamflow trends in two alpine basins of Western Austria
(2017)
Several trend studies have shown that hydrological conditions are changing considerably in the Alpine region. However, the reasons for these changes are only partially understood and trend analyses alone are not able to shed much light. Hydrological modelling is one possible way to identify the trend drivers, i.e., to attribute the detected streamflow trends, given that the model captures all important processes causing the trends. We modelled the hydrological conditions for two alpine catchments in western Austria (a large, mostly lower-altitude catchment with wide valley plains and a nested high-altitude, glaciated headwater catchment) with the distributed, physically-oriented WaSiM-ETH model, which includes a dynamical glacier module. The model was calibrated in a transient mode, i.e., not only on several standard goodness measures and glacier extents, but also in such a way that the simulated streamflow trends fit with the observed ones during the investigation period 1980 to 2007. With this approach, it was possible to separate streamflow components, identify the trends of flow components, and study their relation to trends in atmospheric variables. In addition to trends in annual averages, highly resolved trends for each Julian day were derived, since they proved powerful in an earlier, data-based attribution study. We were able to show that annual and highly resolved trends can be modelled sufficiently well. The results provide a holistic, year-round picture of the drivers of alpine streamflow changes: Higher-altitude catchments are strongly affected by earlier firn melt and snowmelt in spring and increased ice melt throughout the ablation season. Changes in lower-altitude areas are mostly caused by earlier and lower snowmelt volumes. All highly resolved trends in streamflow and its components show an explicit similarity to the local temperature trends. Finally, results indicate that evapotranspiration has been increasing in the lower altitudes during the study period.
Successful delivery of the United Nations sustainable development goals and implementation of the Paris Agreement requires technologies that utilize a wide range of minerals in vast quantities. Metal recycling and technological change will contribute to sustaining supply, but mining must continue and grow for the foreseeable future to ensure that such minerals remain available to industry. New links are needed between existing institutional frameworks to oversee responsible sourcing of minerals, trajectories for mineral exploration, environmental practices, and consumer awareness of the effects of consumption. Here we present, through analysis of a comprehensive set of data and demand forecasts, an interdisciplinary perspective on how best to ensure ecologically viable continuity of global mineral supply over the coming decades.
Mentor Texts
(2017)
Rhizosphere processes are highly dynamic in time and space and strongly depend on each other. Key factors influencing pH changes in the rhizosphere are root exudation, respiration, and nutrient supply, which are influenced by soil water content levels. In this study, we measured the real-time distribution of soil water, pH changes, and oxygen distribution in the rhizosphere of young maize plants using a recently developed imaging approach. Neutron radiography was used to capture the root system and soil water distribution, while fluorescence imaging was employed to map soil pH and soil oxygen changes. Germinated seeds of maize (Zea mays L.) were planted in glass rhizotrons equipped with pH and oxygen-sensitive sensor foils. After 20 d, the rhizotrons were wetted from the bottom and time-lapsed images via fluorescence and neutron imaging were taken during the subsequent day and night cycles for 5 d. We found higher water content and stronger acidification in the first 0.5 mm from the root surface compared to the bulk soil, which could be a consequence of root exudation. While lateral roots only slightly acidified their rhizosphere, crown roots induced stronger acidification of up to 1 pH unit. We observed changing oxygen patterns at different soil moisture conditions and increasing towards lateral as well as crown roots while extending laterally with ongoing water logging. Our work indicates that plants alter the rhizosphere pH and oxygen also depending on root type, which may indirectly arise also from differences in age and water content changes. The results presented here were possible only by combining different imaging techniques to examine profiles at the root-soil interface in a comprehensive way during wetting and drying.
Mantle Flow as a Trigger for Subduction Initiation: A Missing Element of the Wilson Cycle Concept
(2017)
The classical Wilson Cycle concept, describing repeated opening and closing of ocean basins, hypothesizes spontaneous conversion of passive continental margins into subduction zones. This process, however, is impeded by the high strength of passive margins, and it has never occurred in Cenozoic times. Here using thermomechanical models, we show that additional forcing, provided by mantle flow, which is induced by neighboring subduction zones and midmantle slab remnants, can convert a passive margin into a subduction zone. Models suggest that this is a long-term process, thus explaining the lack of Cenozoic examples. We speculate that new subduction zones may form in the next few tens of millions of years along the Argentine passive margin and the U.S. East Coast. Mantle suction force can similarly trigger subduction initiation along large oceanic fracture zones. We propose that new subduction zones will preferentially originate where subduction zones were active in the past, thus explaining the remarkable colocation of subduction zones during at least the last 400 Myr.
Carbon (C) stored in soils represents the largest C pool of terrestrial ecosystems and consequently plays a crucial role in the global C cycle. So far, it is widely unclear to what extent different land uses and land use change influence soil C storage. The hummocky ground moraine landscape of northeastern Germany is characterized by distinct small-scale soil heterogeneity on the one hand, and intensive energy crop cultivation on the other. Both factors are assumed to significantly influence gaseous C exchange; as such, they likely drive soil organic carbon (SOC) stock dynamics in terrestrial agricultural ecosystems. To date, it is not clear to what extent N fertilization forms, which are associated with energy crop cultivation (e.g., application of biogas fermentation residues) and soil type relative to soil erosion state, influence soil C dynamics, nor is it clear whether one of these factors is more important than the other. To investigate the influence of soil erosion state and N fertilization form on soil C dynamics, we present dynamic and seasonal net ecosystem carbon balances (NECB) as a proxy for changes in soil organic carbon stocks. Measurements were conducted for maize (Zea mays L.) at five sites in the "CarboZALF-D" experimental field during the 2011 growing season. Measurement sites represent different soil erosion states (non-eroded Albic Luvisols, extremely eroded Calcaric Regosols and depositional Endogleyic Colluvic Regosols) and N fertilization forms (100% mineral fertilizer, 50% mineral and 50% organic fertilizer, and 100% organic fertilizer). Fertilization treatments were established on the Albic Luvisol. Net ecosystem CO2 exchange (NEE) and ecosystem respiration (R-eco) were measured every four weeks using a dynamic flow-through non-steady-state closed manual chamber system. Gap filling was performed based on empirical temperature and PAR dependency functions and was used to derive daily NEE values. In parallel, daily above-ground biomass production (NPFshoot) was estimated using a logistic growth equation, fitted on periodic biomass samples. Finally, C dynamics were calculated as the balance of daily NEE and NPPshoot based on the initial C input due to organic fertilization. Resulting NECB varied from pronounced soil C losses at the Endogleyic Colluvic Regosol (592 g C m(-2)) to soil C gains at the Calcaric Regosol (-124 g C m(-2)). Minor to modest C losses were observed for the Albic Luvisol. Compared to N fertilization forms, soil erosion states generally had a stronger impact on derived NECB. However, interannual variations in plant phonology and interactions between soil erosion states and fertilization forms might result in different NECB values over multiple years. Hence, long-term measurements of different fertilization treatments on characteristic soil landscape elements are needed.
The characteristics of a landscape pose essential factors for hydrological processes. Therefore, an adequate representation of the landscape of a catchment in hydrological models is vital. However, many of such models exist differing, amongst others, in spatial concept and discretisation. The latter constitutes an essential pre-processing step, for which many different algorithms along with numerous software implementations exist. In that context, existing solutions are often model specific, commercial, or depend on commercial back-end software, and allow only a limited or no workflow automation at all. Consequently, a new package for the scientific software and scripting environment R, called lumpR, was developed. lumpR employs an algorithm for hillslope-based landscape discretisation directed to large-scale application via a hierarchical multi-scale approach. The package addresses existing limitations as it is free and open source, easily extendible to other hydrological models, and the workflow can be fully automated. Moreover, it is user-friendly as the direct coupling to a GIS allows for immediate visual inspection and manual adjustment. Sufficient control is furthermore retained via parameter specification and the option to include expert knowledge. Conversely, completely automatic operation also allows for extensive analysis of aspects related to landscape discretisation. In a case study, the application of the package is presented. A sensitivity analysis of the most important discretisation parameters demonstrates its efficient workflow automation. Considering multiple streamflow metrics, the employed model proved reasonably robust to the discretisation parameters. However, parameters determining the sizes of subbasins and hillslopes proved to be more important than the others, including the number of representative hillslopes, the number of attributes employed for the lumping algorithm, and the number of sub-discretisations of the representative hillslopes.
The characteristics of a landscape pose essential factors for hydrological processes. Therefore, an adequate representation of the landscape of a catchment in hydrological models is vital. However, many of such models exist differing, amongst others, in spatial concept and discretisation. The latter constitutes an essential pre-processing step, for which many different algorithms along with numerous software implementations exist. In that context, existing solutions are often model specific, commercial, or depend on commercial back-end software, and allow only a limited or no workflow automation at all.
Consequently, a new package for the scientific software and scripting environment R, called lumpR, was developed. lumpR employs an algorithm for hillslope-based landscape discretisation directed to large-scale application via a hierarchical multi-scale approach. The package addresses existing limitations as it is free and open source, easily extendible to other hydrological models, and the workflow can be fully automated. Moreover, it is user-friendly as the direct coupling to a GIS allows for immediate visual inspection and manual adjustment. Sufficient control is furthermore retained via parameter specification and the option to include expert knowledge. Conversely, completely automatic operation also allows for extensive analysis of aspects related to landscape discretisation.
In a case study, the application of the package is presented. A sensitivity analysis of the most important discretisation parameters demonstrates its efficient workflow automation. Considering multiple streamflow metrics, the employed model proved reasonably robust to the discretisation parameters. However, parameters determining the sizes of subbasins and hillslopes proved to be more important than the others, including the number of representative hillslopes, the number of attributes employed for the lumping algorithm, and the number of sub-discretisations of the representative hillslopes.
The characteristics of a landscape pose essential factors for hydrological processes. Therefore, an adequate representation of the landscape of a catchment in hydrological models is vital. However, many of such models exist differing, amongst others, in spatial concept and discretisation. The latter constitutes an essential pre-processing step, for which many different algorithms along with numerous software implementations exist. In that context, existing solutions are often model specific, commercial, or depend on commercial back-end software, and allow only a limited or no workflow automation at all.
Consequently, a new package for the scientific software and scripting environment R, called lumpR, was developed. lumpR employs an algorithm for hillslope-based landscape discretisation directed to large-scale application via a hierarchical multi-scale approach. The package addresses existing limitations as it is free and open source, easily extendible to other hydrological models, and the workflow can be fully automated. Moreover, it is user-friendly as the direct coupling to a GIS allows for immediate visual inspection and manual adjustment. Sufficient control is furthermore retained via parameter specification and the option to include expert knowledge. Conversely, completely automatic operation also allows for extensive analysis of aspects related to landscape discretisation.
In a case study, the application of the package is presented. A sensitivity analysis of the most important discretisation parameters demonstrates its efficient workflow automation. Considering multiple streamflow metrics, the employed model proved reasonably robust to the discretisation parameters. However, parameters determining the sizes of subbasins and hillslopes proved to be more important than the others, including the number of representative hillslopes, the number of attributes employed for the lumping algorithm, and the number of sub-discretisations of the representative hillslopes.
The effects of coupling between different layers of the atmosphere during Stratospheric Sudden Warming (SSW) events have been studied quite extensively in the past fewyears, and in this context large lunitidal enhancements in the equatorial ionosphere have also been widely discussed. In this study we report about the longitudinal variabilities in lunitidal enhancement in the equatorial electrojet (EEJ) during SSWs through ground and space observations in the Peruvian and Indian sectors. We observe that the amplification of lunitidal oscillations in EEJ is significantly larger over the Peruvian sector in comparison to the Indian sector. We further compare the lunitidal oscillations in both the sectors during the 2005-2006 and 2008-2009 major SSW events and during a non-SSW winter of 2006-2007. It is found that the lunitidal amplitude in EEJ over the Peruvian sector showed similar enhancements during both the major SSWs, but the enhancements were notably different in the Indian sector. Independent from SSW events, we have also performed a climatological analysis of the lunar modulation of the EEJ during December solstice over both the sectors by using 10years of CHAMP magnetic measurements and found larger lunitidal amplitudes over the Peruvian sector confirming the results from ground magnetometer observations. We have also analyzed the semidiurnal lunar tidal amplitude in neutral temperature measurements from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) at 110km and found lesser longitudinal variability than the lunitidal amplitude in EEJ. Our results suggest that the longitudinal variabilities in lunitidal modulation of the EEJ during SSWs could be related to electrodynamics in the E region dynamo.
The ionosphere, which is strongly influenced by the Sun, is known to be also affected by meteorological processes. These processes, despite having their origin in the troposphere and stratosphere, interact with the upper atmosphere. Such an interaction between atmospheric layers is known as vertical coupling. During geomagnetically quiet times, when near-Earth space is not under the influence of solar storms, these processes become important drivers for ionospheric variability. Studying the link between these processes in the lower atmosphere and the ionospheric variability is important for our understanding of fundamental mechanisms in ionospheric and meteorological research.
A prominent example of vertical coupling between the stratosphere and the ionosphere are the so-called stratospheric sudden warming (SSW) events that occur usually during northern winters and result in an increase in the polar stratospheric temperature and a reversal of the circumpolar winds. While the phenomenon of SSW is confined to the northern polar stratosphere, its influence on the ionosphere can be observed even at equatorial latitudes. During SSW events, the connection between the polar stratosphere and the equatorial ionosphere is believed to be through the modulation of global atmospheric tides. These tides are fundamental for the ionospheric E-region wind dynamo that generates electric fields and currents in the ionosphere. Observations of ionospheric currents indicate a large enhancement of the semidiurnal lunar tide in response to SSW events. Thus, the semidiurnal lunar tide becomes an important driver of ionospheric variability during SSW events.
In this thesis, the ionospheric effect of SSW events is investigated in the equatorial region, where a narrow but an intense E-region current known as the equatorial electrojet (EEJ) flows above the dip equator during the daytime. The day-to-day variability of the EEJ can be determined from magnetic field records at geomagnetic observatories close to the dip equator. Such magnetic data are available for several decades and allows to investigate the impact of SSW events on the EEJ and, even more importantly, helps in understanding the effects of SSW events on the equatorial ionosphere. An excellent long-term record of the geomagnetic field at the equator from 1922 onwards is available for the observatory Huancayo in Peru and is extensively utilized in this study.
The central subject of this thesis is the investigation of lunar tides in the EEJ during SSW events by analyzing long time series. This is done by estimating the lunar tidal amplitude in the EEJ from the magnetic records at Huancayo and by comparing them to measurements of the polar stratospheric wind and temperature, which led to the identification of the known SSW events from 1952 onwards. One goal of this thesis is to identify SSW events that predate 1952. To this end, superposed epoch analysis (SEA) is employed to establish a relationship between the lunar tidal power and the wind and temperature conditions in the lower atmosphere. A threshold value for the lunar tidal power is identified that is discriminative for the known SSW events. This threshold is then used to identify lunar tidal enhancements, which are indicative for any historic SSW events prior to 1952. It can be shown, that the number of lunar tidal enhancements and thus the occurrence frequency of historic SSW events between 1926 and 1952 is similar to the occurrence frequency of the known SSW events from 1952 onwards.
Next to the classic SSW definition, the concept of polar vortex weakening (PVW) is utilized in this thesis. PVW is defined for higher latitudes and altitudes (≈ 40km) than the classical SSW definition (≈ 32km). The correlation between the timing and magnitude of lunar tidal enhancements in the EEJ and the timing and magnitude of PVW is found to be better than for the classic SSW definition. This suggests that the lunar tidal enhancements in the EEJ are closely linked to the state of the middle atmosphere.
Geomagnetic observatories located in different longitudes at the dip equator allow investigating the longitudinally dependent variability of the EEJ during SSW events. For this purpose, the lunar tidal enhancements in the EEJ are determined for the Peruvian and Indian sectors during the major SSW events of the years 2006 and 2009. It is found that the lunar tidal amplitude shows similar enhancements in the Peruvian sector during both SSW events, while the enhancements are notably different for the two events in the Indian sector.
In summary, this thesis shows that lunar tidal enhancements in the EEJ are indeed correlated to the occurrence of SSW events and they should be considered a prominent driver of low latitude ionospheric variability. Secondly, lunar tidal enhancements are found to be longitudinally variable. This suggests that regional effects, such as ionospheric conductivity and the geometry and strength of the geomagnetic field, also play an important role and have to be considered when investigating the mechanisms behind vertical coupling.
Scarce research about small European rivers from non-human impacted areas to determine their natural background state has been undertaken. During the annual hydrological cycle of 2008-9 the patterns of particulate supply (SPM, POC, PON, Al, Cd, Co, Cr, Cu, Fe, Ni, Pb, V, Zn) from the rivers Sor, Mera Landro, Lourido and Landoi to the Northern Galician Rias (SW Bay of Biscay) were tackled. No differences in the composition of the SPM were detected for the studied rivers regarding Al, Fe and POC but the relative percentage of particulate trace elements (PTE) discriminate the rivers. So, Cr, Co and Ni in the Lourido, and Landoi rivers, and Cu in the Mera River, are controlled by watershed minerals of Ortegal Geological Complex while for the rest rivers PTE are by granitic and Ollo de Sapo bedrock watershed. Therefore, the imprint of PTE in the parental rocks of the river basins is reflected on the coastal sediments of the Rias. The main process controlling the dynamics and variations of chemical elements in the particulate form is the river discharge. This fact exemplifies that these rivers presents a natural behavior not being highly influenced by anthropogenic activities.
Lithospheric plates move over the low viscosity asthenosphere balancing several forces. The driving forces include basal shear stress exerted by mantle convection and plate boundary forces such as slab pull and ridge push, whereas the resisting forces include inter-plate friction, trench resistance, and cratonic root resistance. These generate plate motions, the lithospheric stress field and dynamic topography which are observed with different geophysical methods. The orientation and tectonic regime of the observed crustal/lithospheric stress field further contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. Using numerical models previous studies were able to identify major forces generating stresses in the crust and lithosphere which also contribute to the formation of topography as well as driving lithospheric plates. They showed that the first-order stress pattern explaining about 80\,\% of the stress field originates from a balance of forces acting at the base of the moving lithospheric plates due to convective flow in the underlying mantle. The remaining second-order stress pattern is due to lateral density variations in the crust and lithosphere in regions of pronounced topography and high gravitational potential, such as the Himalayas and mid-ocean ridges. By linking global lithosphere dynamics to deep mantle flow this study seeks to evaluate the influence of shallow and deep density heterogenities on plate motions, lithospheric stress field and dynamic topography using the geoid as a major constraint for mantle rheology. We use the global 3D lithosphere-asthenosphere model SLIM3D with visco-elasto-plastic rheology coupled at 300 km depth to a spectral model of mantle flow. The complexity of the lithosphere-asthenosphere component allows for the simulation of power-law rheology with creep parameters accounting for both diffusion and dislocation creep within the uppermost 300 km.
First we investigate the influence of intra-plate friction and asthenospheric viscosity on present-day plate motions. Previous modelling studies have suggested that small friction coefficients (µ < 0.1, yield stress ~ 100 MPa) can lead to plate tectonics in models of mantle convection. Here we show that, in order to match present-day plate motions and net rotation, the frictional parameter must be less than 0.05. We are able to obtain a good fit with the magnitude and orientation of observed plate velocities (NUVEL-1A) in a no-net-rotation (NNR) reference frame with µ < 0.04 and minimum asthenosphere viscosity ~ 5*10e19 Pas to 10e20 Pas. Our estimates of net rotation (NR) of the lithosphere suggest that amplitudes ~ 0.1-0.2 °/Ma, similar to most observation-based estimates, can be obtained with asthenosphere viscosity cutoff values of ~ 10e19 Pas to 5*10e19 Pas and friction coefficient µ < 0.05.
The second part of the study investigates further constraints on shallow and deep mantle heterogeneities causing plate motion by predicting lithosphere stress field and topography and validating with observations. Lithosphere stresses and dynamic topography are computed using the modelling setup and rheological parameters for prescribed plate motions. We validate our results with the World Stress Map 2016 (WSM2016) and the observed residual topography. Here we tested a number of upper mantle thermal-density structures. The one used to calculate plate motions is considered the reference thermal-density structure. This model is derived from a heat flow model combined with a sea floor age model. In addition we used three different thermal-density structures derived from global S-wave velocity models to show the influence of lateral density heterogeneities in the upper 300 km on model predictions. A large portion of the total dynamic force generating stresses in the crust/lithosphere has its origin in the deep mantle, while topography is largely influenced by shallow heterogeneities. For example, there is hardly any difference between the stress orientation patterns predicted with and without consideration of the heterogeneities in the upper mantle density structure across North America, Australia, and North Africa. However, the crust is dominant in areas of high altitude for the stress orientation compared to the all deep mantle contribution.
This study explores the sensitivity of all the considered surface observables with regards to model parameters providing insights into the influence of the asthenosphere and plate boundary rheology on plate motion as we test various thermal-density structures to predict stresses and topography.
This work focuses on the incision process over the Tuostai anticline, a fold of the proximal structure Belt I in the northern Chinese Tian Shan foreland, where the Sikeshu River has incised deeply into the alluvial gravels and the fold's underlying bedrock strata. Field investigation and geomorphic mapping define five terraces of the Sikeshu River (designated as T1 to T5 from oldest to youngest) preserved within the Tuostai anticline. 10Be surface exposure dating and optically stimulated luminescence dating constrain stabilization of the highest three terrace surfaces at about 80 ka (T1), 16 ka (T2), and 15 ka (T3), respectively. Around 16 ka, the calculated river incision rates significantly increase from <2 mm/yr to >6 mm/yr. Undeformed longitudinal profiles of terraces T2, T3 and T4 over the Tuostai anticline suggest that this structure may have been tectonically inactive since stabilization of these three terraces. We thus think that the observed rapid river incision over the Tuostai anticline has not been largely forced by tectonic uplift. Instead, the progressively warmer and wetter palaeoclimatic condition within the Tian Shan range and its surrounding area during the period of ∼20–10 ka may have enhanced river incision across the Tuostai anticline. A reduced sediment/water ratio might have lowered the gradient of the Sikeshu River.
The Himalaya has a major influence on global and regional climate, in particular on the Asian monsoon system. The foreland basin of the Himalaya contains a record of tectonics and paleoclimate since the Miocene. Previous work on the evolution of vegetation and climate has focused on the central and western Himalaya, where a shift from C3 to C4 vegetation has been observed at similar to 7 Ma and linked to increased seasonality, but the climatic evolution of the eastern part of the orogen is less well understood. In order to track vegetation as a marker of monsoon intensity and seasonality, we analyzed delta C-13 and 8180 values of soil carbonate and associated delta C-13 values of bulk organic carbon from previously dated sedimentary sections exposing the syn-orogenic detrital Dharamsala and Siwalik Groups in the west, and, for the first time, the Siwalik Group in the east of the Himalayan foreland basin. Sedimentary records span from 20 to 1 Myr in the west (Joginder Nagar, Jawalamukhi, and Haripur Kolar sections) and from 13 to 1 Myr in the east (Kameng section), respectively. The presence of soil carbonate in the west and its absence in the east is a first indication of long-term lateral climatic variation, as soil carbonate requires seasonally arid conditions to develop. delta C-13 values in soil carbonate show a shift from around -10 parts per thousand to -2 parts per thousand at similar to 7 Ma in the west, which is confirmed by delta C-13 analyses on bulk organic carbon that show a shift from around -23 parts per thousand to -19 parts per thousand at the same time. Such a shift in isotopic values is likely to be associated with a change from C3 to C4 vegetation. In contrast, delta C-13 values of bulk organic carbon remain at 23 parts per thousand o in the east. Thus, our data show that the current east -west variation in climate was established at similar to 7 Ma. We propose that the regional change towards a more seasonal climate in the west is linked to a decrease of the influence of the Westerlies, delivering less winter precipitation to the western Himalaya, while the east remained annually humid due to its proximity to the monsoonal moisture source. (C) 2017 Elsevier B.V. All rights reserved.
The Indian Summer Monsoon (ISM) is one of the most important climate systems, whose variability and driving mechanisms are of broad interest for academic and societal communities. Here, we present a well-dated high-resolution pollen analysis from a 4.82-m long sediment core taken from Basomtso, in the southeastern Tibetan Plateau (TP), which depicts the regional climate changes of the past millennium. Our results show that subalpine coniferous forest was dominant around Basomtso from ca. 867 to ca. 750 cal. yr BP, indicating a warm and semi-humid climate. The timberline in the study area significantly decreased from ca. 750 to ca.100 cal. yr BP, and a cold climate, corresponding to the Little Ice Age (LIA) prevailed. Since ca. 100 cal. yr BP, the vegetation type changed to forest-meadow with rising temperatures and moisture. Ordination analysis reveals that the migration of vegetation was dominated by regional temperatures and then by moisture. Further comparisons between the Basomtso pollen record and the regional temperature reconstructions underscore the relevance of the Basomtso record from the southeastern TP for regional and global climatologies. Our pollen based moisture reconstruction demonstrates the strong multicentennial-scale link to ISM variability, providing solid evidence for the increase of monsoonal strengths over the past four centuries. Spectral analysis indicates the potential influence of solar forcing. However, a closer relationship has been observed between multicentennial ISM variations and Indian Ocean sea surface temperature anomalies (SSTs), suggesting that the variations in monsoonal precipitation over the southeastern TP are probably driven by the Indian Ocean Dipole on the multicentennial scale. (C) 2017 Elsevier Ltd. All rights reserved.
Uplift of the Al Hajar Mountains in Oman has been related to either Late Cretaceous ophiolite obduction or the Neogene Zagros collision. To test these hypotheses, the cooling of the central Al Hajar Mountains is constrained by 10 apatite (U-Th)/He (AHe), 15 fission track (AFT), and four zircon (U-Th)/He (ZHe) sample ages. These data show differential cooling between the two major structural culminations of the mountains. In the 3km high Jabal Akhdar culmination AHe single-grain ages range between 392 Ma and 101 Ma (2 sigma errors), AFT ages range from 518 Ma to 324 Ma, and ZHe single-grain ages range from 62 +/- 3Ma to 39 +/- 2 Ma. In the 2 km high Saih Hatat culmination AHe ages range from 26 +/- 4 to 12 +/- 4 Ma, AFT ages from 73 +/- 19Ma to 57 +/- 8 Ma, and ZHe single-grain ages from 81 +/- 4 Ma to 58 +/- 3 Ma. Thermal modeling demonstrates that cooling associated with uplift and erosion initiated at 40 Ma, indicating that uplift occurred 30 Myr after ophiolite obduction and at least 10 Myr before the Zagros collision. Therefore, this uplift cannot be related to either event. We propose that crustal thickening supporting the topography of the Al Hajar Mountains was caused by a slowdown of Makran subduction and that north Oman took up the residual fraction of N-S convergence between Arabia and Eurasia.
Lakes are a ubiquitous landscape feature in northern permafrost regions. They have a strong impact on carbon, energy and water fluxes and can be quite responsive to climate change. The monitoring of lake change in northern high latitudes, at a sufficiently accurate spatial and temporal resolution, is crucial for understanding the underlying processes driving lake change. To date, lake change studies in permafrost regions were based on a variety of different sources, image acquisition periods and single snapshots, and localized analysis, which hinders the comparison of different regions. Here, we present a methodology based on machine-learning based classification of robust trends of multi-spectral indices of Landsat data (TM, ETM+, OLI) and object-based lake detection, to analyze and compare the individual, local and regional lake dynamics of four different study sites (Alaska North Slope, Western Alaska, Central Yakutia, Kolyma Lowland) in the northern permafrost zone from 1999 to 2014. Regional patterns of lake area change on the Alaska North Slope (-0.69%), Western Alaska (-2.82%), and Kolyma Lowland (-0.51%) largely include increases due to thermokarst lake expansion, but more dominant lake area losses due to catastrophic lake drainage events. In contrast, Central Yakutia showed a remarkable increase in lake area of 48.48%, likely resulting from warmer and wetter climate conditions over the latter half of the study period. Within all study regions, variability in lake dynamics was associated with differences in permafrost characteristics, landscape position (i.e., upland vs. lowland), and surface geology. With the global availability of Landsat data and a consistent methodology for processing the input data derived from robust trends of multi-spectral indices, we demonstrate a transferability, scalability and consistency of lake change analysis within the northern permafrost region.
The development of well-constrained palaeo-proxies that enable the reconstruction of past climate change is becoming an ever more important field of scientific enquiry within the palaeobotanical community, with the potential to deliver broader impacts linked to understanding of future anthropogenic climate change. One of the major uncertainties in predicting climate change is how the hydrological cycle will respond to future warming. Griener and Warny (2015, Review of Palaeobotany and Palynology 221,138-143) suggested that pollen size might be a useful proxy for tracking moisture availability, as pollen size appears to be negatively correlated with moisture. Given the long fossil record of pollen and spores such a proxy would have broad scope and the potential to deliver much needed information. Here we set out to fully evaluate and test the robustness of this proxy. We focus on a number of key issues: controls on pollen size, data analysis, and finally proxy validation. Using this approach we find that there is little theoretical or empirical support for the original relationship proposed by Griener and Warny. Consequently it is currently premature to use pollen size as a moisture availability proxy in the fossil record. However, we recognise that the technique may have potential and conclude by offering a series of recommendations that would rigorously assess and test for a relationship between pollen size and moisture availability. (c) 2017 Elsevier B.V. All rights reserved.
The Makran accretionary prism in SE Iran and SW Pakistan is one of the most extensive subduction accretions on Earth. It is characterized by intense folding, thrust faulting and dislocation of the Cenozoic units that consist of sedimentary, igneous and metamorphic rocks. Rock units forming the northern Makran ophiolites are amalgamated as a melange. Metamorphic rocks, including greenschist, amphibolite and blueschist, resulted from metamorphism of mafic rocks and serpentinites. In spite of the geodynamic significance of blueschist in this area, it has been rarely studied. Peak metamorphic phases of the northern Makran mafic blueschist in the Iranshahr area are glaucophane, phengite, quartz +/- omphacite+epidote. Post peak minerals are chlorite, albite and calcic amphibole. Blueschist facies metasedimentary rocks contain garnet, phengite, albite and epidote in the matrix and as inclusions in glaucophane. The calculated P-T pseudosection for a representative metabasic glaucophane schist yields peak pressure and temperature of 11.5-15kbar at 400-510 degrees C. These rocks experienced retrograde metamorphism from blueschist to greenschist facies (350-450 degrees C and 7-8kbar) during exhumation. A back arc basin was formed due to northward subduction of Neotethys under Eurasia (Lut block). Exhumation of the high-pressure metamorphic rocks in northern Makran occurred contemporarily with subduction. Several reverse faults played an important role in exhumation of the ophiolitic and HP-LT rocks. The presence of serpentinite shows the possible role of a serpentinite diapir for exhumation of the blueschist. A tectonic model is proposed here for metamorphism and exhumation of oceanic crust and accretionary sedimentary rocks of the Makran area. Vast accretion of subducted materials caused southward migration of the shore.
Both Alpine and Mediterranean areas are considered sensitive to so-called global change, considered as the combination of climate and land use changes. All panels on climate evolution predict future scenarios of increasing frequency and magnitude of floods which are likely to lead to huge geomorphic adjustments of river channels so major metamorphosis of fluvial systems is expected as a result of global change. Such pressures are likely to give rise to major ecological and economic changes and challenges that governments need to address as a matter of priority. Changes in river flow regimes associated with global change are therefore ushering in a new era, where there is a critical need to evaluate hydro-geomorphological hazards from headwaters to lowland areas (flooding can be not just a problem related to being under the water). A key question is how our understanding of these hazards associated with global change can be improved; improvement has to come from integrated research which includes the climatological and physical conditions that could influence the hydrology and sediment generation and hence the conveyance of water and sediments (including the river’s capacity, i.e. amount of sediment, and competence, i.e. channel deformation) and the vulnerabilities and economic repercussions of changing hydrological hazards (including the evaluation of the hydro-geomorphological risks too).
Within this framework, the purpose of this international symposium is to bring together researchers from several disciplines as hydrology, fluvial geomorphology, hydraulic engineering, environmental science, geography, economy (and any other related discipline) to discuss the effects of global change over the river system in relation with floods. The symposium is organized by means of invited talks given by prominent experts, oral lectures, poster sessions and discussion sessions for each individual topic; it will try to improve our understanding of how rivers are likely to evolve as a result of global change and hence address the associated hazards of that fluvial environmental change concerning flooding.
Four main topics are going to be addressed:
- Modelling global change (i.e. climate and land-use) at relevant spatial (regional, local) and temporal (from the long-term to the single-event) scales.
- Measuring and modelling river floods from the hydrological, sediment transport (both suspended and bedload) and channel morphology points of view at different spatial (from the catchment to the reach) and temporal (from the long-term to the single-event) scales.
- Evaluation and assessment of current and future river flooding hazards and risks in a global change perspective.
- Catchment management to face river floods in a changing world.
We are very pleased to welcome you to Potsdam. We hope you will enjoy your participation at the International Symposium on the Effects of Global Change on Floods, Fluvial Geomorphology and Related Hazards in Mountainous Rivers and have an exciting and profitable experience. Finally, we would like to thank all speakers, participants, supporters, and sponsors for their contributions that for sure will make of this event a very remarkable and fruitful meeting. We acknowledge the valuable support of the European Commission (Marie Curie Intra-European Fellowship, Project ‘‘Floodhazards’’, PIEF-GA-2013-622468, Seventh EU Framework Programme) and the Deutschen Forschungsgemeinschaft (Research Training Group “Natural Hazards and Risks in a Changing World” (NatRiskChange; GRK 2043/1) as the symposium would not have been possible without their help. Without your cooperation, this symposium would not be either possible or successful.
Integration and development of the energy supply in China and worldwide is a challenge for the years to come. The innovative idea presented here is based on an extension of the “power-to-gas-to-power” technology by establishing a closed carbon cycle. It is an implementation of a low-carbon energy system based on carbon dioxide capture and storage (CCS) to store and reuse wind and solar energy. The Chenjiacun storage project in China compares well with the German case study for the towns Potsdam and Brandenburg/Havel in the Federal State of Brandenburg based on the Ketzin pilot site for CCS.
Near-surface geophysical techniques are extensively used in a variety of engineering, environmental, geologic, and hydrologic applications. While many of these applications ask for detailed, quantitative models of selected material properties, geophysical data are increasingly used to estimate such target properties. Typically, this estimation procedure relies on a two-step workflow including (1) the inversion of geophysical data and (2) the petrophysical translation of the inverted parameter models into the target properties. Standard deterministic implementations of such a quantitative interpretation result in a single best-estimate model, often without considering and propagating the uncertainties related to the two steps. We address this problem by using a rather novel, particle-swarm-based global joint strategy for data inversion and by implementing Monte Carlo procedures for petrophysical property estimation. We apply our proposed workflow to crosshole ground-penetrating radar, P-, and S-wave data sets collected at a well-constrained test site for a detailed geotechnical characterization of unconsolidated sands. For joint traveltime inversion, the chosen global approach results in ensembles of acceptable velocity models, which are analyzed to appraise inversion-related uncertainties. Subsequently, the entire ensembles of inverted velocity models are considered to estimate selected petrophysical properties including porosity, bulk density, and elastic moduli via well-established petrophysical relations implemented in a Monte Carlo framework. Our results illustrate the potential benefit of such an advanced interpretation strategy; i.e., the proposed workflow allows to study how uncertainties propagate into the finally estimated property models, while concurrently we are able to study the impact of uncertainties in the used petrophysical relations (e.g., the influence of uncertain, user-specified parameters). We conclude that such statistical approaches for the quantitative interpretation of geophysical data can be easily extended and adapted to other applications and geophysical methods and might be an important step toward increasing the popularity and acceptance of geophysical tools in engineering practice.
A series of large-magnitude earthquakes above 6.9 occurred in the northern Tien-Shan between 1885 and 1911. The Chilik earthquake of 11 July 1889, has been listed with a magnitude of 8.3, based on sparse macroseismic intensities, constrained by reported damage. Despite the existence of several juvenile fault scarps in the epicentral region, that are possibly associated with the 1889 earthquake, no through-going surface rupture having the dimensions expected for a magnitude 8.3 earthquake has been located - a puzzling dilemma. Could the magnitude have been overestimated? This would have major implications not only for the understanding of the earthquake series, but also for regional hazard estimates. Fortunately, a fragmentary record from an early Rebeur-Paschwitz seismometer exists for the Chilik event, recorded in Wilhelmshaven (Germany). To constrain the magnitude, we compare the late coda waves of this record with those of recent events from Central Asia, recorded on modern instruments in Germany and filtered with Rebeur-Paschwitz instrument characteristics. Additional constraints come from disturbances of historic magnetograms that exist from the Chilik and the 1911 Chon-Kemin earthquakes. Scaling of these historic records confirm a magnitude of about 8 for the 1889 Chilik earthquake, pointing towards a lower crustal contribution to the fault area.
We analyzed chlorophyll-a and Colored Dissolved Organic Matter (CDOM) dynamics from field measurements and assessed the potential of multispectral satellite data for retrieving water-quality parameters in three small surface reservoirs in the Brazilian semiarid region. More specifically, this work is comprised of: (i) analysis of Chl-a and trophic dynamics; (ii) characterization of CDOM; (iii) estimation of Chl-a and CDOM from OLI/Landsat-8 and RapidEye imagery. The monitoring lasted 20 months within a multi-year drought, which contributed to water-quality deterioration. Chl-a and trophic state analysis showed a highly eutrophic status for the perennial reservoir during the entire study period, while the non-perennial reservoirs ranged from oligotrophic to eutrophic, with changes associated with the first events of the rainy season. CDOM characterization suggests that the perennial reservoir is mostly influenced by autochthonous sources, while allochthonous sources dominate the non-perennial ones. Spectral-group classification assigned the perennial reservoir as a CDOM-moderate and highly eutrophic reservoir, whereas the non-perennial ones were assigned as CDOM-rich and oligotrophic-dystrophic reservoirs. The remote sensing initiative was partially successful: the Chl-a was best modelled using RapidEye for the perennial one; whereas CDOM performed best with Landsat-8 for non-perennial reservoirs. This investigation showed potential for retrieving water quality parameters in dry areas with small reservoirs.
In the last few years the method of cosmic-ray neutron sensing (CRNS) has gained popularity among hydrologists, physicists, and land-surface modelers. The sensor provides continuous soil moisture data, averaged over several hectares and tens of decimeters in depth. However, the signal still may contain unidentified features of hydrological processes, and many calibration datasets are often required in order to find reliable relations between neutron intensity and water dynamics. Recent insights into environmental neutrons accurately described the spatial sensitivity of the sensor and thus allowed one to quantify the contribution of individual sample locations to the CRNS signal. Consequently, data points of calibration and validation datasets are suggested to be averaged using a more physically based weighting approach. In this work, a revised sensitivity function is used to calculate weighted averages of point data. The function is different from the simple exponential convention by the extraordinary sensitivity to the first few meters around the probe, and by dependencies on air pressure, air humidity, soil moisture, and vegetation. The approach is extensively tested at six distinct monitoring sites: two sites with multiple calibration datasets and four sites with continuous time series datasets. In all cases, the revised averaging method improved the performance of the CRNS products. The revised approach further helped to reveal hidden hydrological processes which otherwise remained unexplained in the data or were lost in the process of overcalibration. The presented weighting approach increases the overall accuracy of CRNS products and will have an impact on all their applications in agriculture, hydrology, and modeling.
Pollen-based quantitative reconstructions of past climate variables is a standard palaeoclimatic approach. Despite knowing that the spatial extent of the calibration-set affects the reconstruction result, guidance is lacking as to how to determine a suitable spatial extent of the pollen-climate calibration-set. In this study, past mean annual precipitation (P-ann) during the Holocene (since 11.5 cal ka BP) is reconstructed repeatedly for pollen records from Qinghai Lake (36.7 degrees N, 100.5 degrees E; north-east Tibetan Plateau), Gonghai Lake (38.9 degrees N, 112.2 degrees E; north China) and Sihailongwan Lake (42.3 degrees N, 126.6 degrees E; north-east China) using calibration-sets of varying spatial extents extracted from the modern pollen dataset of China and Mongolia (2559 sampling sites and 168 pollen taxa in total). Results indicate that the spatial extent of the calibration-set has a strong impact on model performance, analogue quality and reconstruction diagnostics (absolute value, range, trend, optimum). Generally, these effects are stronger with the modern analogue technique (MAT) than with weighted averaging partial least squares (WA-PLS). With respect to fossil spectra from northern China, the spatial extent of calibration-sets should be restricted to radii between ca. 1000 and 1500 km because small-scale calibration-sets (<800 km radius) will likely fail to include enough spatial variation in the modern pollen assemblages to reflect the temporal range shifts during the Holocene, while too broad a scale calibration-set (>1500 km radius) will include taxa with very different pollen-climate relationships. (C) 2017 Elsevier Ltd. All rights reserved.
Temperature is a key factor controlling plant growth and vitality in the temperate climates of the mid-latitudes like in vast parts of the European continent. Beyond the effect of average conditions, the timings and magnitudes of temperature extremes play a particularly crucial role, which needs to be better understood in the context of projected future rises in the frequency and/or intensity of such events. In this work, we employ event coincidence analysis (ECA) to quantify the likelihood of simultaneous occurrences of extremes in daytime land surface temperature anomalies (LSTAD) and the normalized difference vegetation index (NDVI). We perform this analysis for entire Europe based upon remote sensing data, differentiating between three periods corresponding to different stages of plant development during the growing season. In addition, we analyze the typical elevation and land cover type of the regions showing significantly large event coincidences rates to identify the most severely affected vegetation types. Our results reveal distinct spatio-temporal impact patterns in terms of extraordinarily large co-occurrence rates between several combinations of temperature and NDVI extremes. Croplands are among the most frequently affected land cover types, while elevation is found to have only a minor effect on the spatial distribution of corresponding extreme weather impacts. These findings provide important insights into the vulnerability of European terrestrial ecosystems to extreme temperature events and demonstrate how event-based statistics like ECA can provide a valuable perspective on environmental nexuses.
This study examines the characteristics of drought in the Volta River Basin (VRB), investigates the influence of drought on the streamflow, and projects the impacts of future climate change on the drought. A combination of observation data and regional climate simulations of past and future climates (1970-2013, 2046-2065, and 2081-2100) were analyzed for the study. The Standardized Precipitation Index (SPI) and Standardized Precipitation and Evapotranspiration (SPEI) were used to characterize drought while the Standardized Runoff Index (SRI) were used to quantify runoff. Results of the study show that the historical pattern of drought is generally consistent with previous studies over the Basin and most part of West Africa. RCA ensemble medians (RMED) give realistic simulations of drought characteristics and area extent over the Basin and the sub-catchments in the past climate. Generally, an increase in drought intensity and spatial extent are projected over VRB for SPEI and SPI, but the magnitude of increase is higher with SPEI than with SPI. Drought frequency (events per decade) may be magnified by a factor of 1.2, (2046-2065) to 1.6 (2081-2100) compared to the present day episodes in the basin. The coupling between streamflow and drought episodes was very strong (P < 0.05) for the 1-16-year band before the 1970 but showed strong correlation all through the time series period for the 4-8 -years band. Runoff was highly sensitive to precipitation in the VRB and a 2-3 month time lag was found between drought indices and streamflow in the Volta River Basin. Results of this study may guide policymakers in planning how to minimize the negative impacts of future climate change that could have consequences on agriculture, water resources and energy supply.
Understanding how Earth-surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment "uxes. Sedimentary records provide the archives for inferring these processes, but their interpretation is compromised by our incomplete understanding of how sediment-routing systems respond to millennial-scale climate cycles. We analyzed seven sediment cores recovered from marine turbidite depositional sites along the Chile continental margin. The sites span a pronounced arid-to-humid gradient with variable relief and related sediment connectivity of terrestrial and marine environments. These sites allowed us to study event related depositional processes in different climatic and geomorphic settings from the Last Glacial Maximum to the present day. The three sites reveal a steep decline of turbidite deposition during deglaciation. High rates of sea-level rise postdate the decline in turbidite deposition. Comparison with paleoclimate proxies documents that the spatio-temporal sedimentary pattern rather mirrors the deglacial humidity decrease and concomitant warming with no resolvable lag times. Our results let us infer that declining deglacial humidity decreased "uvial sediment supply. This signal propagated rapidly through the highly connected systems into the marine sink in north-central Chile. In contrast, in south-central Chile, connectivity between the Andean erosional zone and the "uvial transfer zone probably decreased abruptly by sediment trapping in piedmont lakes related to deglaciation, resulting in a sudden decrease of sediment supply to the ocean. Additionally, reduced moisture supply may have contributed to the rapid decline of turbidite deposition. These different causes result in similar depositional patterns in the marine sinks. We conclude that turbiditic strata may constitute reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions. However, the underlying causes for similar signal manifestations in the sinks may differ, ranging from maintained high system connectivity to abrupt connectivity loss. (C) 2017 Elsevier B.V. All rights reserved.
In hydrological models, parameters are used to represent the time-invariant characteristics of catchments and to capture different aspects of hydrological response. Hence, model parameters need to be identified based on their role in controlling the hydrological behaviour. For the identification of meaningful parameter values, multiple and complementary performance criteria are used that compare modelled and measured discharge time series. The reliability of the identification of hydrologically meaningful model parameter values depends on how distinctly a model parameter can be assigned to one of the performance criteria.& para;& para;To investigate this, we introduce the new concept of connective strength between model parameters and performance criteria. The connective strength assesses the intensity in the interrelationship between model parameters and performance criteria in a bijective way. In our analysis of connective strength, model simulations are carried out based on a latin hypercube sampling. Ten performance criteria including Nash-Sutcliffe efficiency (NSE), Kling-Gupta efficiency (KGE) and its three components (alpha, beta and r) as well as RSR (the ratio of the root mean square error to the standard deviation) for different segments of the flow duration curve (FDC) are calculated.& para;& para;With a joint analysis of two regression tree (RT) approaches, we derive how a model parameter is connected to different performance criteria. At first, RTs are constructed using each performance criterion as the target variable to detect the most relevant model parameters for each performance criterion. Secondly, RTs are constructed using each parameter as the target variable to detect which performance criteria are impacted by changes in the values of one distinct model parameter. Based on this, appropriate performance criteria are identified for each model parameter.& para;& para;In this study, a high bijective connective strength between model parameters and performance criteria is found for low- and mid-flow conditions. Moreover, the RT analyses emphasise the benefit of an individual analysis of the three components of KGE and of the FDC segments. Furthermore, the RT analyses highlight under which conditions these performance criteria provide insights into precise parameter identification. Our results show that separate performance criteria are required to identify dominant parameters on low- and mid-flow conditions, whilst the number of required performance criteria for high flows increases with increasing process complexity in the catchment. Overall, the analysis of the connective strength between model parameters and performance criteria using RTs contribute to a more realistic handling of parameters and performance criteria in hydrological modelling.
High Mountain Asia (HMA) – encompassing the Tibetan Plateau and surrounding mountain ranges – is the primary water source for much of Asia, serving more than a billion downstream users. Many catchments receive the majority of their yearly water budget in the form of snow, which is poorly monitored by sparse in situ weather networks. Both the timing and volume of snowmelt play critical roles in downstream water provision, as many applications – such as agriculture, drinking-water generation, and hydropower – rely on consistent and predictable snowmelt runoff. Here, we examine passive microwave data across HMA with five sensors (SSMI, SSMIS, AMSR-E, AMSR2, and GPM) from 1987 to 2016 to track the timing of the snowmelt season – defined here as the time between maximum passive microwave signal separation and snow clearance. We validated our method against climate model surface temperatures, optical remote-sensing snow-cover data, and a manual control dataset (n = 2100, 3 variables at 25 locations over 28 years); our algorithm is generally accurate within 3–5 days. Using the algorithm-generated snowmelt dates, we examine the spatiotemporal patterns of the snowmelt season across HMA. The climatically short (29-year) time series, along with complex interannual snowfall variations, makes determining trends in snowmelt dates at a single point difficult. We instead identify trends in snowmelt timing by using hierarchical clustering of the passive microwave data to determine trends in self-similar regions. We make the following four key observations. (1) The end of the snowmelt season is trending almost universally earlier in HMA (negative trends). Changes in the end of the snowmelt season are generally between 2 and 8 days decade−1 over the 29-year study period (5–25 days total). The length of the snowmelt season is thus shrinking in many, though not all, regions of HMA. Some areas exhibit later peak signal separation (positive trends), but with generally smaller magnitudes than trends in snowmelt end. (2) Areas with long snowmelt periods, such as the Tibetan Plateau, show the strongest compression of the snowmelt season (negative trends). These trends are apparent regardless of the time period over which the regression is performed. (3) While trends averaged over 3 decades indicate generally earlier snowmelt seasons, data from the last 14 years (2002–2016) exhibit positive trends in many regions, such as parts of the Pamir and Kunlun Shan. Due to the short nature of the time series, it is not clear whether this change is a reversal of a long-term trend or simply interannual variability. (4) Some regions with stable or growing glaciers – such as the Karakoram and Kunlun Shan – see slightly later snowmelt seasons and longer snowmelt periods. It is likely that changes in the snowmelt regime of HMA account for some of the observed heterogeneity in glacier response to climate change. While the decadal increases in regional temperature have in general led to earlier and shortened melt seasons, changes in HMA's cryosphere have been spatially and temporally heterogeneous.
In this study, an in situ application for identifying neodymium (Nd) enriched surface materials that uses multitemporal hyperspectral images is presented (HySpex sensor). Because of the narrow shape and shallow absorption depth of the neodymium absorption feature, a method was developed for enhancing and extracting the necessary information for neodymium from image spectra, even under illumination conditions that are not optimal. For this purpose, the two following approaches were developed: (1) reducing noise and analyzing changing illumination conditions by averaging multitemporal image scenes and (2) enhancing the depth of the desired absorption band by deconvolving every image spectrum with a Gaussian curve while the rest of the spectrum remains unchanged (Richardson-Lucy deconvolution). To evaluate these findings, nine field samples from the Fen complex in Norway were analyzed using handheld X-ray fluorescence devices and by conducting detailed laboratory-based geochemical rare earth element determinations. The result is a qualitative outcrop map that highlights zones that are enriched in neodymium. To reduce the influences of non-optimal illumination, particularly at the studied site, a minimum of seven single acquisitions is required. Sharpening the neodymium absorption band allows for robust mapping, even at the outer zones of enrichment. From the geochemical investigations, we found that iron oxides decrease the applicability of the method. However, iron-related absorption bands can be used as secondary indicators for sulfidic ore zones that are mainly enriched with rare earth elements. In summary, we found that hyperspectral spectroscopy is a noninvasive, fast and cost-saving method for determining neodymium at outcrop surfaces
The fusion of hyperspectral imaging (HSI) sensor and airborne lidar scanner (ALS) data provides promising potential for applications in environmental sciences. Standard fusion approaches use reflectance information from the HSI and distance measurements from the ALS to increase data dimen-sionality and geometric accuracy. However, the potential for data fusion based on the respective intensity information of the complementary active and passive sensor systems is high and not yet fully exploited. Here, an approach for the rigorous illumination correction of HSI data, based on the radiometric cross-calibrated return intensity information of ALS data, is presented. The cross calibration utilizes a ray tracing-based fusion of both sensor measurements by intersecting their particular beam shapes. The developed method is capable of compensating for the drawbacks of passive HSI systems, such as cast and cloud shadowing effects, illumination changes over time, across track illumination, and partly anisotropy effects. During processing, spatial and temporal differences in illumination patterns are detected and corrected over the entire HSI wavelength domain. The improvement in the classification accuracy of urban and vegetation surfaces demonstrates the benefit and potential of the proposed HSI illumination correction. The presented approach is the first step toward the rigorous in-flight fusion of passive and active system characteristics, enabling new capabilities for a variety of applications.
One of the most significant Late Holocene climate shifts occurred around 2800 years ago, when cooler and wetter climate conditions established in western Europe. This shift coincided with an abrupt change in regional atmospheric circulation between 2760 and 2560 cal years BP, which has been linked to a grand solar minimum with the same duration (the Homeric Minimum). We investigated the temporal sequence of hydroclimatic and vegetation changes across this interval of climatic change (Homeric climate oscillation) by using lipid biomarker stable hydrogen isotope ratios (ED values) and pollen assemblages from the annually-laminated sediment record from lake Meerfelder Maar (Germany). Over the investigated interval (3200-2000 varve years BP), terrestrial lipid biomarker ED showed a gradual trend to more negative values, consistent with the western Europe long-term climate trend of the Late Holocene. At ca. 2640 varve years BP we identified a strong increase in aquatic plants and algal remains, indicating a rapid change in the aquatic ecosystem superimposed on this long-term trend. Interestingly, this aquatic ecosystem change was accompanied by large changes in ED values of aquatic lipid biomarkers, such as nC(21) and nC(23) (by between 22 and 30%(0)). As these variations cannot solely be explained by hydroclimate changes, we suggest that these changes in the Wag value were influenced by changes in n-alkane source organisms. Our results illustrate that if ubiquitous aquatic lipid biomarkers are derived from a limited pool of organisms, changes in lake ecology can be a driving factor for variations on sedimentary lipid MN values, which then could be easily misinterpreted in terms of hydro climatic changes. (C) 2017 Elsevier Ltd. All rights reserved.
Tropical peatlands now emit hundreds of megatons of carbon dioxide per year because of human disruption of the feedbacks that link peat accumulation and groundwater hydrology. However, no quantitative theory has existed for how patterns of carbon storage and release accompanying growth and subsidence of tropical peatlands are affected by climate and disturbance. Using comprehensive data from a pristine peatland in Brunei Darussalam, we show how rainfall and groundwater flow determine a shape parameter (the Laplacian of the peat surface elevation) that specifies, under a given rainfall regime, the ultimate, stable morphology, and hence carbon storage, of a tropical peatland within a network of rivers or canals. We find that peatlands reach their ultimate shape first at the edges of peat domes where they are bounded by rivers, so that the rate of carbon uptake accompanying their growth is proportional to the area of the still-growing dome interior. We use this model to study how tropical peatland carbon storage and fluxes are controlled by changes in climate, sea level, and drainage networks. We find that fluctuations in net precipitation on timescales from hours to years can reduce long-term peat accumulation. Our mathematical and numerical models can be used to predict long-term effects of changes in temporal rainfall patterns and drainage networks on tropical peatland geomorphology and carbon storage.
The majority of original seismograms recorded at the very beginning of instrumental seismology (the early 1900s) did not survive till present. However, a number of books, bulletins, and catalogs were published including the seismogram reproductions of some, particularly interesting earthquakes. In case these reproductions contain the time and amplitude scales, they can be successfully analyzed the same way as the original records. Information about the Atushi (Kashgar) earthquake, which occurred on August 22, 1902, is very limited. We could not find any original seismograms for this earthquake, but 12 seismograms from 6 seismic stations were printed as example records in different books. These data in combination with macroseismic observations and different bulletins information published for this earthquake were used to determine the source parameters of the earthquake. The earthquake epicenter was relocated at 39.87A degrees N and 76.42A degrees E with the hypocenter depth of about 18 km. We could further determine magnitudes m (B) = 7.7 +/- 0.3, M (S) = 7.8 +/- 0.4, M (W) = 7.7 +/- 0.3 and the focal mechanism of the earthquake with strike/dip/rake - 260A degrees +/- 20/30A degrees +/- 10/90A degrees +/- 10. This study confirms that the earthquake likely had a smaller magnitude than previously reported (M8.3). The focal mechanism indicates dominant thrust faulting, which is in a good agreement with presumably responsible Tuotegongbaizi-Aerpaleike northward dipping thrust fault kinematic, described in previous studies.
This study demonstrates the potential of using single-pass TanDEM-X (TDX) radar imagery to analyse inter- and intra-annual glacier changes in mountainous terrain. Based on SAR images acquired in February 2012, March 2013 and November 2013 over the Inylchek Glacier, Kyrgyzstan, we discuss in detail the processing steps required to generate three reliable digital elevation models (DEMs) with a spatial resolution of 10 m that can be used for glacial mass balance studies. We describe the interferometric processing steps and the influence of a priori elevation information that is required to model long wavelength topographic effects. We also focus on DEM alignment to allow optimal DEM comparisons and on the effects of radar signal penetration on ice and snow surface elevations. We finally compare glacier elevation changes between the three TDX DEMs and the C-band shuttle radar topography mission (SRTM) DEM from February 2000. We introduce a new approach for glacier elevation change calculations that depends on the elevation and slope of the terrain. We highlight the superior quality of the TDX DEMs compared to the SRTM DEM, describe remaining DEM uncertainties and discuss the limitations that arise due to the side-looking nature of the radar sensor. (C) 2017 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS). Published by Elsevier B.V. All rights reserved.
In 2009, a group of prominent Earth scientists introduced the "planetary boundaries" (PB) framework: they suggested nine global control variables, and defined corresponding "thresholds which, if crossed, could generate unacceptable environmental change". The concept builds on systems theory, and views Earth as a complex adaptive system in which anthropogenic disturbances may trigger non-linear, abrupt, and irreversible changes at the global scale, and "push the Earth system outside the stable environmental state of the Holocene". While the idea has been remarkably successful in both science and policy circles, it has also raised fundamental concerns, as the majority of suggested processes and their corresponding planetary boundaries do not operate at the global scale, and thus apparently lack the potential to trigger abrupt planetary changes.
This paper picks up the debate with specific regard to the planetary boundary on "global freshwater use". While the bio-physical impacts of excessive water consumption are typically confined to the river basin scale, the PB proponents argue that water-induced environmental disasters could build up to planetary-scale feedbacks and system failures. So far, however, no evidence has been presented to corroborate that hypothesis. Furthermore, no coherent approach has been presented to what extent a planetary threshold value could reflect the risk of regional environmental disaster. To be sure, the PB framework was revised in 2015, extending the planetary freshwater boundary with a set of basin-level boundaries inferred from environmental water flow assumptions. Yet, no new evidence was presented, either with respect to the ability of those basin-level boundaries to reflect the risk of regional regime shifts or with respect to a potential mechanism linking river basins to the planetary scale.
So while the idea of a planetary boundary on freshwater use appears intriguing, the line of arguments presented so far remains speculative and implicatory. As long as Earth system science does not present compelling evidence, the exercise of assigning actual numbers to such a boundary is arbitrary, premature, and misleading. Taken as a basis for water-related policy and management decisions, though, the idea transforms from misleading to dangerous, as it implies that we can globally offset water-related environmental impacts. A planetary boundary on freshwater use should thus be disapproved and actively refuted by the hydrological and water resources community.
In 2009, a group of prominent Earth scientists introduced the "planetary boundaries" (PB) framework: they suggested nine global control variables, and defined corresponding "thresholds which, if crossed, could generate unacceptable environmental change". The concept builds on systems theory, and views Earth as a complex adaptive system in which anthropogenic disturbances may trigger non-linear, abrupt, and irreversible changes at the global scale, and "push the Earth system outside the stable environmental state of the Holocene". While the idea has been remarkably successful in both science and policy circles, it has also raised fundamental concerns, as the majority of suggested processes and their corresponding planetary boundaries do not operate at the global scale, and thus apparently lack the potential to trigger abrupt planetary changes.
This paper picks up the debate with specific regard to the planetary boundary on "global freshwater use". While the bio-physical impacts of excessive water consumption are typically confined to the river basin scale, the PB proponents argue that water-induced environmental disasters could build up to planetary-scale feedbacks and system failures. So far, however, no evidence has been presented to corroborate that hypothesis. Furthermore, no coherent approach has been presented to what extent a planetary threshold value could reflect the risk of regional environmental disaster. To be sure, the PB framework was revised in 2015, extending the planetary freshwater boundary with a set of basin-level boundaries inferred from environmental water flow assumptions. Yet, no new evidence was presented, either with respect to the ability of those basin-level boundaries to reflect the risk of regional regime shifts or with respect to a potential mechanism linking river basins to the planetary scale.
So while the idea of a planetary boundary on freshwater use appears intriguing, the line of arguments presented so far remains speculative and implicatory. As long as Earth system science does not present compelling evidence, the exercise of assigning actual numbers to such a boundary is arbitrary, premature, and misleading. Taken as a basis for water-related policy and management decisions, though, the idea transforms from misleading to dangerous, as it implies that we can globally offset water-related environmental impacts. A planetary boundary on freshwater use should thus be disapproved and actively refuted by the hydrological and water resources community.
In 2009, a group of prominent Earth scientists introduced the "planetary boundaries" (PB) framework: they suggested nine global control variables, and defined corresponding "thresholds which, if crossed, could generate unacceptable environmental change". The concept builds on systems theory, and views Earth as a complex adaptive system in which anthropogenic disturbances may trigger nonlinear, abrupt, and irreversible changes at the global scale, and "push the Earth system outside the stable environmental state of the Holocene". While the idea has been remarkably successful in both science and policy circles, it has also raised fundamental concerns, as the majority of suggested processes and their corresponding planetary boundaries do not operate at the global scale, and thus apparently lack the potential to trigger abrupt planetary changes. This paper picks up the debate with specific regard to the planetary boundary on "global freshwater use". While the bio-physical impacts of excessive water consumption are typically confined to the river basin scale, the PB proponents argue that water-induced environmental disasters could build up to planetary-scale feedbacks and system failures. So far, however, no evidence has been presented to corroborate that hypothesis. Furthermore, no coherent approach has been presented to what extent a planetary threshold value could reflect the risk of regional environmental disaster. To be sure, the PB framework was revised in 2015, extending the planetary freshwater boundary with a set of basin-level boundaries inferred from environmental water flow assumptions. Yet, no new evidence was presented, either with respect to the ability of those basin-level boundaries to reflect the risk of regional regime shifts or with respect to a potential mechanism linking river basins to the planetary scale. So while the idea of a planetary boundary on freshwater use appears intriguing, the line of arguments presented so far remains speculative and implicatory. As long as Earth system science does not present compelling evidence, the exercise of assigning actual numbers to such a boundary is arbitrary, premature, and misleading. Taken as a basis for waterrelated policy and management decisions, though, the idea transforms from misleading to dangerous, as it implies that we can globally offset water-related environmental impacts. A planetary boundary on freshwater use should thus be disapproved and actively refuted by the hydrological and water resources community.
Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the V-s,V-30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data.
Biofilm formation in bacteria is considered to be one strategy to avoid protozoan grazing. However, this assumption is largely based on experiments with suspension-feeding protozoans. Here we test the hypothesis that grazing resistance depends on both the grazers’ feeding trait and the bacterial phenotype, rather than being a general characteristic of bacterial biofilms. We combined batch experiments with mathematical modelling, considering the bacterium Pseudomonas putida and either a suspension-feeding (i.e. the ciliate Paramecium tetraurelia) or a surface-feeding grazer (i.e. the amoeba Acanthamoeba castellanii). We find that both plankton and biofilm phenotypes were consumed, when exposed to their specialised grazer, whereas the other phenotype remained grazing-resistant. This was consistently shown in two experiments (starting with either only planktonic bacteria or with additional pre-grown biofilms) and matches model predictions. In the experiments, the plankton feeder strongly stimulated the biofilm biomass. This stimulation of the resistant prey phenotype was not predicted by the model and it was not observed for the biofilm feeders, suggesting the existence of additional mechanisms that stimulate biofilm formation besides selective feeding. Overall, our results confirm our hypothesis that grazing resistance is a matter of the grazers’ trait (i.e. feeding type) rather than a biofilm-specific property.
Fragmentation of landscapes creates a transition zone in between natural habitats or different kinds of land use. In forested and agricultural landscapes with transition zones, microclimate and matter cycling are markedly altered. This probably accelerates and is intensified by global warming. However, there is no consensus on defining transition zones and quantifying relevant variables for microclimate and matter cycling across disciplines. This article is an attempt to a) revise definitions and offer a framework for quantitative ecologists, b) review the literature on microclimate and matter cycling in transition zones and c) summarise this information using meta-analysis to better understand bio-geochemical and bio-geophysical processes and their spatial extent in transition zones. We expect altered conditions in soils of transition zones to be 10-20 m with a maximum of 50 m, and 25-50 m for above-ground space with a maximum of 125 m.
According to the classical plume hypothesis, mantle plumes are localized upwellings of hot, buoyant material in the Earth’s mantle. They have a typical mushroom shape, consisting of a large plume head, which is associated with the formation of voluminous flood basalts (a Large
Igneous Province) and a narrow plume tail, which generates a linear, age-progressive chain of volcanic edifices (a hotspot track) as the tectonic plate migrates over the relatively stationary plume. Both plume heads and tails reshape large areas of the Earth’s surface over many tens of millions of years.
However, not every plume has left an exemplary record that supports the classical hypothesis. The main objective of this thesis is therefore to study how specific hotspots have created the crustal thickness pattern attributed to their volcanic activities. Using regional geodynamic
models, the main chapters of this thesis address the challenge of deciphering the three individual (and increasingly complex) Réunion, Iceland, and Kerguelen hotspot histories, especially focussing on the interactions between the respective plume and nearby spreading ridges.
For this purpose, the mantle convection code ASPECT is used to set up three-dimensional numerical models, which consider the specific local surroundings of each plume by prescribing time-dependent boundary conditions for temperature and mantle flow. Combining reconstructed plate boundaries and plate motions, large-scale global flow velocities and an inhomogeneous lithosphere thickness distribution together with a dehydration rheology represents a novel setup for regional convection models.
The model results show the crustal thickness pattern produced by the plume, which is compared to present-day topographic structures, crustal thickness estimates and age determinations of volcanic provinces associated with hotspot activity. Altogether, the model results agree well
with surface observations. Moreover, the dynamic development of the plumes in the models provide explanations for the generation of smaller, yet characteristic volcanic features that were previously unexplained. Considering the present-day state of a model as a prediction for the
current temperature distribution in the mantle, it cannot only be compared to observations on the surface, but also to structures in the Earth’s interior as imaged by seismic tomography.
More precisely, in the case of the Réunion hotspot, the model demonstrates how the distinctive gap between the Maldives and Chagos is generated due to the combination of the ridge geometry and plume-ridge interaction. Further, the Rodrigues Ridge is formed as the surface expression
of a long-distance sublithospheric flow channel between the upwelling plume and the closest ridge segment, confirming the long-standing hypothesis of Morgan (1978) for the first time in a dynamic context. The Réunion plume has been studied in connection with the seismological
RHUM-RUM project, which has recently provided new seismic tomography images that yield an excellent match with the geodynamic model.
Regarding the Iceland plume, the numerical model shows how plume material may have accumulated in an east-west trending corridor of thin lithosphere across Greenland and resulted in simultaneous melt generation west and east of Greenland. This provides an explanation for the
extremely widespread volcanic material attributed to magma production of the Iceland hotspot and demonstrates that the model setup is also able to explain more complicated hotspot histories. The Iceland model results also agree well with newly derived seismic tomographic images.
The Kerguelen hotspot has an extremely complex history and previous studies concluded that the plume might be dismembered or influenced by solitary waves in its conduit to produce the reconstructed variable melt production rate. The geodynamic model, however, shows that a constant plume influx can result in a variable magma production rate if the plume interacts with nearby mid-ocean ridges. Moreover, the Ninetyeast Ridge in the model is created by on-ridge activities, while the Kerguelen plume was located beneath the Australian plate. This is also a contrast to earlier studies, which described the Ninetyeast Ridge as the result of the Indian plate passing over the plume. Furthermore, the Amsterdam-Saint Paul Plateau in the model is the result of plume material flowing from the upwelling toward the Southeast Indian Ridge, whereas previous geochemical studies attributed that volcanic province to a separate deep plume.
In summary, the three case studies presented in this thesis consistently highlight the importance of plume-ridge interaction in order to reconstruct the overall volcanic hotspot record as well as specific smaller features attributed to a certain hotspot. They also demonstrate that it is not necessary to attribute highly complicated properties to a specific plume in order to account for complex observations. Thus, this thesis contributes to the general understanding of plume dynamics and extends the very specific knowledge about the Réunion, Iceland, and Kerguelen mantle plumes.
Through the zmir-Ankara-Erzincan and the Vardar oceans suture zones, convergence between the Eurasian and African plates played a key role in controlling Palaeogene magmatism in north-western Anatolia, northern Aegean, and eastern Balkans. LA-ICP-MS dating of U and Pb isotopes on zircon separates from the tuffs of the Harmankaya Volcanic Rocks, which are inter-fingered with the lower-middle Eocene deposits of the Gazikoy Formation to the north of the Ganos Fault and the Karaaac Formation in the Gelibolu Peninsula, yielded a late Ypresian (51Ma) age. The chemical characteristics suggest that the lavas and tuffs of the Harmankaya Volcanic Rocks are products of syn- or post-collision magmas. These volcanic rocks show also close affinities to the subduction-related magmas. In addition to the already known andesitic volcanic rocks, our field observations in Gokceada Island indicate also the existence of granitic and rhyolitic rocks (Marmaros Magmatic Assemblage). Our U-Pb zircon age data has shown that the newly discovered Marmaros granitic plutons intruded during late Oligocene (26Ma) into the deposits of the Karaaac Formation in Gokceada Island. LA-ICP-MS dating of U and Pb isotopes on zircon separates from the Marmaros rhyolitic rocks yielded a late Oligocene (26Ma) crystallization age. Geochemical characteristics indicate that the more-evolved Oligocene granitic and rhyolitic rock of the Marmaros Magmatic Assemblage possibly assimilated a greater amount of crustal material than the lower Eocene Harmankaya Volcanic Rocks. Geochemical features and age relationships suggest increasing amounts of crustal contamination and a decreasing subduction signature during the evolution of magmas in NW Turkey from the early Eocene to the Oligocene. The magmatic activity developed following the northward subduction of the zmir-Ankara-Erzincan oceanic lithosphere and the earliest Palaeocene final continental collision between the Sakarya and Anatolide-Tauride zones.
The increasing numbers of recordings at individual sites allows quantification of empirical linear site-response adjustment factors (delta S2S(s)) from the ground motion prediction equation (GMPE) residuals. The delta S2S(s) are then used to linearly scale the ergodic GMPE predictions to obtain site-specific ground motion predictions in a partially non-ergodic Probabilistic Seismic Hazard Assessment (PSHA). To address key statistical and conceptual issues in the current practice, we introduce a novel empirical region-and site-specific PSHA methodology wherein, (1) site-to-site variability (phi(S2S)) is first estimated as a random-variance in a mixed-effects GMPE regression, (2) delta S2S(s) at new sites with strong motion are estimated using the a priori phi(S2S), and (3) the GMPE site-specific single-site aleatory variability sigma(ss,s) is replaced with a generic site-corrected aleatory variability sigma(0). Comparison of region- and site-specific hazard curves from our method against the traditional ergodic estimates at 225 sites in Europe and Middle East shows an approximate 50% difference in predicted ground motions over a range of hazard levels-a strong motivation to increase seismological monitoring of critical facilities and enrich regional ground motion data sets.
Meteorological extreme events have great potential for damaging railway infrastructure and posing risks to the safety of train passengers. In the future, climate change will presumably have serious implications on meteorological hazards in the Alpine region. Hence, attaining insights on future frequencies of meteorological extremes with relevance for the railway operation in Austria is required in the context of a comprehensive and sustainable natural hazard management plan of the railway operator. In this study, possible impacts of climate change on the frequencies of so-called critical meteorological conditions (CMCs) between the periods 1961-1990 and 2011-2040 are analyzed. Thresholds for such CMCs have been defined by the railway operator and used in its weather monitoring and early warning system. First, the seasonal climate change signals for air temperature and precipitation in Austria are described on the basis of an ensemble of high-resolution Regional Climate Model (RCM) simulations for Europe. Subsequently, the RCM-ensemble was used to investigate changes in the frequency of CMCs. Finally, the sensitivity of results is analyzed with varying threshold values for the CMCs. Results give robust indications for an all-season air temperature rise, but show no clear tendency in average precipitation. The frequency analyses reveal an increase in intense rainfall events and heat waves, whereas heavy snowfall and cold days are likely to decrease. Furthermore, results indicate that frequencies of CMCs are rather sensitive to changes of thresholds. It thus emphasizes the importance to carefully define, validate, andif neededto adapt the thresholds that are used in the weather monitoring and warning system of the railway operator. For this, continuous and standardized documentation of damaging events and near-misses is a pre-requisite.
Low-relief plateaus separated by deeply incised fjords are hallmarks of glaciated, passive continental margins. Spectacular examples fringe the once ice-covered North Atlantic coasts of Greenland, Norway and Canada, but low-relief plateau landscapes also underlie present-day ice sheets in Antarctica and Greenland. Dissected plateaus have long been viewed as the outcome of selective linear erosion by ice sheets that focus incision in glacial troughs, leaving the intervening landscapes essentially unaffected. According to this hypothesis, the plateaus are remnants of preglacial low-relief topography. However, here we use computational experiments to show that, like fjords, plateaus are emergent properties of long-term ice-sheet erosion. Ice sheets can either increase or decrease subglacial relief depending on the wavelength of the underlying topography, and plateau topography arises dynamically from evolving feedbacks between topography, ice dynamics and erosion over million-year timescales. This new mechanistic explanation for plateau formation opens the possibility of plateaus contributing significantly to accelerated sediment flux at the onset of the late Cenozoic glaciations, before becoming stable later in the Quaternary.
Steep mountain channels are an important component of the fluvial system. On geological timescales, they shape mountain belts and counteract tectonic uplift by erosion. Their channels are strongly coupled to hillslopes and they are often the main source of sediment transported downstream to low-gradient rivers and to alluvial fans, where commonly settlements in mountainous areas are located. Hence, mountain streams are the cause for one of the main natural hazards in these regions. Due to climate change and a pronounced populating of mountainous regions the attention given to this threat is even growing. Although quantitative studies on sediment transport have significantly advanced our knowledge on measuring and calibration techniques we still lack studies of the processes within mountain catchments. Studies examining the mechanisms of energy and mass exchange on small temporal and spatial scales in steep streams remain sparse in comparison to low-gradient alluvial channels.
In the beginning of this doctoral project, a vast amount of experience and knowledge of a steep stream in the Swiss Prealps had to be consolidated in order to shape the principal aim of this research effort. It became obvious, that observations from within the catchment are underrepresented in comparison to experiments performed at the catchment’s outlet measuring fluxes and the effects of the transported material. To counteract this imbalance, an examination of mass fluxes within the catchment on the process scale was intended. Hence, this thesis is heavily based on direct field observations, which are generally rare in these environments in quantity and quality. The first objective was to investigate the coupling of the channel with surrounding hillslopes, the major sources of sediment. This research, which involved the monitoring of the channel and adjacent hillslopes, revealed that alluvial channel steps play a key role in coupling of channel and hillslopes. The observations showed that hillslope stability is strongly associated with the step presence and an understanding of step morphology and stability is therefore crucial in understanding sediment mobilization. This finding refined the way we think about the sediment dynamics in steep channels and motivated continued research of the step dynamics. However, soon it became obvious that the technological basis for developing field tests and analyzing the high resolution geometry measured in the field was not available. Moreover, for many geometrical quantities in mountain channels definitions and a clear scientific standard was not available. For example, these streams are characterized by a high spatial variability of the channel banks, preventing straightforward calculations of the channel width without a defined reference. Thus, the second and inevitable part of this thesis became the development and evaluation of scientific tools in order to investigate the geometrical content of the study reach thoroughly. The developed framework allowed the derivation of various metrics of step and channel geometry which facilitated research on the a large data set of observations of channel steps. In the third part, innovative, physically-based metrics have been developed and compared to current knowledge on step formation, suggested in the literature. With this analyses it could be demonstrated that the formation of channel steps follow a wide range of hydraulic controls. Due to the wide range of tested parameters channel steps observed in a natural stream were attributed to different mechanisms of step formation, including those based on jamming and those based on key-stones. This study extended our knowledge on step formation in a steep stream and harmonized different, often time seen as competing, processes of step formation. This study was based on observations collected at one point in time. In the fourth part of this project, the findings of the snap-shot observations were extended in the temporal dimension and the derived concepts have been utilized to investigate reach-scale step patterns in response to large, exceptional flood events. The preliminary results of this work based on the long-term analyses of 7 years of long profile surveys showed that the previously observed channel-hillslope mechanism is the responsible for the short-term response of step formation.
The findings of the long-term analyses of step patterns drew a bow to the initial observations of a channel-hillslope system which allowed to join the dots in the dynamics of steep stream. Thus, in this thesis a broad approach has been chosen to gain insights into the complex system of steep mountain rivers. The effort includes in situ field observations (article I), the development of quantitative scientific tools (article II), the reach-scale analyses of step-pool morphology (article III) and its temporal evolution (article IV). With this work our view on the processes within the catchment has been advanced towards a better mechanistic understanding of these fluvial system relevant to improve applied scientific work.
The study deals with the identification and characterization of rapid subsurface flow structures through pedo- and geo-physical measurements and irrigation experiments at the point, plot and hillslope scale. Our investigation of flow-relevant structures and hydrological responses refers to the general interplay of form and function, respectively. To obtain a holistic picture of the subsurface, a large set of different laboratory, exploratory and experimental methods was used at the different scales. For exploration these methods included drilled soil core profiles, in situ measurements of infiltration capacity and saturated hydraulic conductivity, and laboratory analyses of soil water retention and saturated hydraulic conductivity. The irrigation experiments at the plot scale were monitored through a combination of dye tracer, salt tracer, soil moisture dynamics, and 3-D time-lapse ground penetrating radar (GPR) methods. At the hillslope scale the subsurface was explored by a 3-D GPR survey. A natural storm event and an irrigation experiment were monitored by a dense network of soil moisture observations and a cascade of 2-D time-lapse GPR "trenches". We show that the shift between activated and non-activated state of the flow paths is needed to distinguish structures from overall heterogeneity. Pedo-physical analyses of point-scale samples are the basis for sub-scale structure inference. At the plot and hillslope scale 3-D and 2-D time-lapse GPR applications are successfully employed as non-invasive means to image subsurface response patterns and to identify flow-relevant paths. Tracer recovery and soil water responses from irrigation experiments deliver a consistent estimate of response velocities. The combined observation of form and function under active conditions provides the means to localize and characterize the structures (this study) and the hydrological processes (companion study Angermann et al., 2017, this issue).
The phrase form and function was established in architecture and biology and refers to the idea that form and functionality are closely correlated, influence each other, and co-evolve. We suggest transferring this idea to hydrological systems to separate and analyze their two main characteristics: their form, which is equivalent to the spatial structure and static properties, and their function, equivalent to internal responses and hydrological behavior. While this approach is not particularly new to hydrological field research, we want to employ this concept to explicitly pursue the question of what information is most advantageous to understand a hydrological system. We applied this concept to subsurface flow within a hillslope, with a methodological focus on function: we conducted observations during a natural storm event and followed this with a hillslope-scale irrigation experiment. The results are used to infer hydrological processes of the monitored system. Based on these findings, the explanatory power and conclusiveness of the data are discussed. The measurements included basic hydrological monitoring methods, like piezometers, soil moisture, and discharge measurements. These were accompanied by isotope sampling and a novel application of 2-D time-lapse GPR (ground-penetrating radar). The main finding regarding the processes in the hillslope was that preferential flow paths were established quickly, despite unsaturated conditions. These flow paths also caused a detectable signal in the catchment response following a natural rainfall event, showing that these processes are relevant also at the catchment scale. Thus, we conclude that response observations (dynamics and patterns, i.e., indicators of function) were well suited to describing processes at the observational scale. Especially the use of 2-D time-lapse GPR measurements, providing detailed subsurface response patterns, as well as the combination of stream-centered and hillslope-centered approaches, allowed us to link processes and put them in a larger context. Transfer to other scales beyond observational scale and generalizations, however, rely on the knowledge of structures (form) and remain speculative. The complementary approach with a methodological focus on form (i.e., structure exploration) is presented and discussed in the companion paper by Jackisch et al. (2017).
We analyse current and possible future reforms of the Indian food policies for the most important staple grains, wheat and rice, within a two-commodity dynamic partial equilibrium model with stochastic shocks. The model is empirically grounded and reproduces past values well. It uses a new reduced-form approach to capture private storage dynamics. We evaluate the implementation of the National Food Security Act (NFSA) under several policy measures with the current regime as well as two scenarios with a regime change - implementation of cash transfers and deficiency payments. Implications for market fundamentals and fiscal costs are simulated in the medium term - until 2020/21. The NFSA puts a high pressure on fiscal costs and public stocks. Relying on imports with low support prices results in low fiscal costs and stable, but higher domestic and international prices, and a high risk of zero stocks. A policy strategy to manipulate procurement prices in order to maintain public stocks close to the norms leads to slightly higher fiscal costs with lower, but more volatile prices. The highest domestic price volatility occurs under a strategy which uses export bans in order to maintain sufficient public stocks. A cash-based regime can bring considerable savings and curb fiscal costs, particularly if targeted to the poor, and would leave sufficient stocks due to higher private stocks.
Eleven inverse isochron ages from total fusion and three from stepwise heating analyses fit the age model. Four experiments resulted in older inverse isochron ages that do not concur with the model within 2 sigma uncertainties and that deviate from 1 ka to 17 ka minimum. C-and R-type zoning are interpreted as representing growth in magma chamber cupolas, as wall mushes, or in narrow conduits. Persistent compositions of PO-type crystals and abundant surfaces recording dissolution features correspond to formation within a magma chamber. C-type zoning and R-type zoning have revealed an irregular incorporation of melt and fluid inclusions. These two types of zoning in feldspar are interpreted as preferentially contributing either heterogeneously distributed excess Ar-40 or inherited Ar-40 to the deviating Ar-40/Ar-39 ages that are discussed in this study. (C) 2017 Elsevier Ltd. All rights reserved.
Electromagnetic induction (EMI) sensors using sufficiently low-frequency harmonic sources and sufficiently small loop separations operate in the low-induction-number (LIN) domain for a relatively wide range of background conductivity. These systems are used in diverse near-surface investigations including applications from soil sciences, hydrology, and archaeology. The special case of portable multiconfiguration EMI sensors operating at frequencies <= 20 kHz offers the possibility of using a fast linear deconvolution method to interpret multichannel data sets in three dimensions. Here, we have developed a fast 3D inversion/deconvolution method regularized with 3D smoothness constraints and formulated in the hybrid spectral-spatial domain. Compared with other linear approaches, the spectral-spatial domain formulation significantly reduces the computational cost of the processing and opens the door for real-time 3D interpretation of large data sets consisting of more than 100,000 data points. First, we test our proposed algorithm on synthetic data sets computed with the full Maxwell theory. Then, we apply our method to a real four-configuration EMI data set acquired to map the thickness of peat layers embedded in a sandy environment. For the synthetic and the field example, we compared our result with the result obtained using a standard point-by-point 1D nonlinear inversion approach. This comparison demonstrates that the proposed methodology provides superior lateral resolution compared with the 1D nonlinear inversion, at the same time significantly reducing the computational cost of the processing.
Flood risk management in Europe and worldwide is not static but constantly in a state of flux. There has been a trend towards more integrated flood risk management in many countries. However, the initial situation and the pace and direction of change is very different in the various countries. In this paper, we will present a conceptual framework that seeks to explain why countries opt for different flood risk management portfolios. The developed framework utilises insights from a range of policy science concepts in an integrated way and considers, among others, factors such as geographical characteristics, the experience with flood disasters, as well as human behavioural aspects.
The crystallization kinetics of silicate liquids were studied experimentally in the system haplogranite-B-Li-H2O, at variable degrees of undercooling and variable water concentration. We investigated the kinetics of nucleation and crystallization of unseeded synthetic hydrous haplogranite with 1 wt % Li2O + 2 center dot 3 wt % B2O3 added (composition C1) and 2 wt % Li2O + 4 center dot 6 wt % B2O3 added (composition C2). Compositions C1 and C2 are simplified representative bulk compositions of Li-rich pegmatites and their highly differentiated cores, respectively. Starting water contents varied between 3 and 9 wt %. With few exceptions, the system remained water-undersaturated. About 86 isothermal runs of 1-60 days duration, grouped in 25 time series of constant temperature and initial H2O content, were carried out at temperatures from 400 to 700A degrees C at 300 MPa, corresponding to variable degrees of undercooling between the liquidus and glass transition. Viscosity measurements indicate that the glass transition for both compositions is below 400A degrees C for 3 wt % water and below 300A degrees C for 6 center dot 5 wt % water. The melts remained virtually crystal free at 400A degrees C, about 100A degrees C and 120A degrees C above the glass transition for compositions C1 and C2, respectively, in experiments up to 30 days long. This result is consistent with the existence of low-temperature, undercooled melts in the crust. At lower values of undercooling the runs crystallized partially, up to about 70% volume fraction. Undercooling and the amount of water are the main factors controlling nucleation and growth rates, and therefore textures. Minerals nucleate and grow sequentially according to mineral-specific nucleation delays. The mineral assemblage started with Li-Al stuffed quartz (in C1) and virgilite (in C2), solid-solutions between quartz and gamma-spodumene. The quartz-like phases were typically followed by spherulitic alkali feldspar-quartz intergrowths, euhedral petalite, and fine-grained muscovite. Nearly pure quartz formed as rims and replacement of metastable virgilite and stuffed quartz, in particular at the boron- and water-rich crystallization front of large feldspar or petalite. With the exception of muscovite, all minerals nucleated heterogeneously, on the capsule wall or on pre-existing minerals, and grew inwards, towards the capsule center. Experimental textures resembled the textures of zoned pegmatites, including skeletal, graphic, unidirectional, radiating, spherulitic, massive, and replacement textures. In some cases, when fluid saturation was reached, miarolitic cavities developed containing euhedral crystals. Although unidirectional growth rates appeared to slow down in time, volumetric rates for stable graphic alkali-feldspar quartz intergrowths and petalite remained constant for up to 60 days and similar to 70% crystallization. Metastable stuffed quartz and virgilite diminished in their growth rates in runs of 30 days or longer, were resorbed in the melt, and were partially replaced by second-generation quartz. Unobstructed, self-sustained crystal growth in conditions of very low nucleation density appears to be the dominant mechanism to form giant pegmatitic crystals, although experimental growth rates are much slower than predicted in nature based on conductive-cooling models.
The Acheulian site of Gesher Benot Ya‘aqov (GBY) in the Upper Jordan Valley revealed important data on environment and material culture, as well as evidence for hominin behavioural and cognitive patterns documented at the margins of the Hula Palaeo-lake. A 50 m long core (GBY#2) drilled at the archaeological site has provided a long Pleistocene geological, environmental and climatological record, which expands the existing knowledge of hominin-habitat relationships. Bracketed by two basalt flows dated by 40Ar/39Ar and based on the identification of the Matuyama-Brunhes Boundary (MBB) and correlation with the GBY excavation site, the sedimentary sequence provides the climatic history around the MBB. Multi-proxy data including pollen and non-pollen palynomorphs, macro-botanical remains, molluscs and ostracods provide evidence for lake and lake-margin environments during Marine Isotope Stages (MIS) 20 and 19. Semi-moist conditions were followed by a pronounced dry phase during MIS 20, and warm and moist conditions with Quercus-Pistacia woodlands prevailed during MIS 19. In contrast to the reconstructed climate change from relatively dry to moister conditions, the depositional environment developed from an open-water lake during MIS 20 to a lake margin environment in MIS 19. Generally shallower conditions at the core site in MIS 19 resulted from the progradation of the lake shore due to the filling of the basin. Micro-charcoal analysis suggests a likelihood of human-induced fire in some parts of the core, which can be correlated with artefact-containing layers of the GBY excavation site. The Hula Palaeo-lake region provided an ideal niche for hominins and other vertebrates during global glacial-interglacial climate fluctuations at the end of the Early Pleistocene.
Information about the hydrological behaviour of a river basin prior to setting up, calibrating and validating a distributed hydrological model requires extensive datasets that are hardly available for many parts of the world due to insufficient monitoring networks. In this study, the focus was on prevailing spatio-temporal patterns of remotely sensed evapotranspiration (ET) that enabled conclusions to be drawn about the hydrological behaviour and spatial peculiarities of a river basin at rather high spatial resolution. The prevailing spatio-temporal patterns of ET were identified using a principal component analysis of a time series of 644 images of MODIS ET covering the Wami River basin (Tanzania) between the years 2000 and 2013. The time series of the loadings on the principal components were analysed for seasonality and significant long-term trends. The spatial patterns of principal component scores were tested for significant correlation with elevations and slopes, and for differences between different soil texture and land use classes. The results inferred that the temporal and spatial patterns of ET were related to those of preceding rainfalls. At the end of the dry season, high ET was maintained only in areas of shallow groundwater and in cloud forest nature reserves. A region of clear reduction of ET in the long-term was related to massive land use change. The results also confirmed that most soil texture and land use classes differed significantly. Moreover, ET was exceptionally high in natural forests and loam soil, and very low in bushland and sandy-loam soil. Clearly, this approach has shown great potential of publicly available remote sensing data in providing a sound basis for water resources management as well as for distributed hydrological models in data-scarce river basins at lower latitudes.
Background. Metal recycling factories (MRFs) have developed rapidly in Nigeria as recycling policies have been increasingly embraced. These MRFs are point sources for introducing potentially toxic elements (PTEs) into environmental media. Objectives. The aim of this study was to determine the constituents (elemental and mineralogy) of the wastes (slag and particulate matter, (PM)) and soils around the MRFs and to determine the level of pollution within the area. Methods. Sixty samples (30 slag samples, 15 soil samples and 15 PM samples) were collected for this study. The soils, slag and PM samples were analyzed for elemental constituents using inductively coupled plasma optical emission spectrometry. Mineralogy of the PM was determined using scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), and soil mineralogy was determined by an X-ray diffractometer (XRD). Results. The results of the soil analyses revealed the following concentrations for the selected metals in mg/kg include lead (Pb) (21.0-2399.0), zinc (Zn) (56.0-4188.0), copper (Cu) (10.0-1470.0), nickel (Ni) (6.0-215.0), chromium (Cr) (921.0-1737.0) and cadmium (Cd) (below detectable limit (Bdl)-18.1). For the slags the results were Pb (68.0-.333.0), Zn (1364.0-3062), Cu (119.0-1470.0), Ni (12.0-675.0), Cr (297-1737) and Cd (Bdl-15.8). The results in mu g/g for the metal analysis in PM were Pb (4.6-160.0), Zn (18.0-471.0), Cu (2.5-11.0), Ni (0.8-4.2), and Cr (2.5-11.0), while Cd was undetected. The slags are currently utilized for filling the foundations of buildings and roads, providing additional pathways for the introduction of PTEs into the environment from the suspended materials generated from mechanical breakdown of the slags. Conclusions. The MRFs were found to have impacted the quality of environmental media through the introduction of PTEs, impairing soil quality, in addition to PM, which can have detrimental health consequences. Further studies on the health implications of these pollutants and their impacts on human health are needed. Competing Interests. The authors declare no competing financial interests
The application of heat as a hydrological tracer has become a standard method for quantifying water fluxes between groundwater and surface water. The typical application is to estimate vertical water fluxes in the shallow subsurface beneath streams or lakes. For this purpose, time series of temperatures in the surface water and in the sediment are measured and evaluated by a vertical 1D representation of heat transport by advection and conduction. Several analytical solutions exist to calculate the vertical water flux from the measured temperatures. Although analytical solutions can be easily implemented, they are restricted to specific boundary conditions such as a sinusoidal upper temperature boundary. Numerical solutions offer higher flexibility in the selection of the boundary conditions. This, in turn, reduces the effort of data preprocessing, such as the extraction of the diurnal temperature variation from the raw data. Here, we present software to estimate water fluxes based on temperaturesFLUX-BOT. FLUX-BOT is a numerical code written in MATLAB that calculates vertical water fluxes in saturated sediments based on the inversion of measured temperature time series observed at multiple depths. FLUX-BOT applies a centred Crank-Nicolson implicit finite difference scheme to solve the one-dimensional heat advection-conduction equation. FLUX-BOT includes functions for the inverse numerical routines, functions for visualizing the results, and a function for performing uncertainty analysis. We present applications of FLUX-BOT to synthetic and to real temperature data to demonstrate its performance.
Rotations of the principal stress axes are observed as a result of fluid injection into reservoirs. We use a generic, fully coupled 3-D thermo-hydro-mechanical model to investigate systematically the dependence of this stress rotation on different reservoir properties and injection scenarios. We find that permeability, injection rate, and initial differential stress are the key factors, while other reservoir properties only play a negligible role. In particular, we find that thermal effects do not significantly contribute to stress rotations. For reservoir types with usual differential stress and reservoir treatment the occurrence of significant stress rotations is limited to reservoirs with a permeability of less than approximately 10(-12)m(2). Higher permeability effectively prevents stress rotations to occur. Thus, according to these general findings, the observed principal stress axes rotation can be used as a proxy of the initial differential stress provided that rock permeability and fluid injection rate are known a priori.
An understanding of the relationship between canopy structure and the water balance is needed for predicting how forest structure changes affect rainfall partitioning and, consequently, water resources. The objective of this study was to predict rainfall interception (I) and canopy storage capacity (S) using canopy structure variables and to investigate how seasonal changes influence their relationship. The study was conducted in twelve 50 m x 50 m plots in the Zagros forest in the western Iranian state of Ilam, protected forests of Dalab region. Average cumulative I was 84.2mm, accounting for 10.2% of cumulative gross precipitation (GP) over a 1-year period. Using a regression based method, S averaged similar to 1 mm and 0.1 mm in the leafed and leafless periods, respectively. There were no relationships between tree density and I: GP or S, but I: GP and S increased with leaf area index, canopy cover fraction, basal area, tree height, and diameter at breast height in the leafed period. In addition, wood area index and canopy cover fraction were related to I: GP or S in the leafless period. (C) 2017 Elsevier B.V. All rights reserved.
This article offers a reconstruction of the vegetation and climate of the south-western Siberian Baraba forest-steppe area during the last ca. 8000 years. The analysis of palynological data from the sediment core of Lake Bolshie Toroki using quantitative methods has made it possible to reconstruct changes of the dominant types of vegetation and mean July air temperatures. Coniferous forests grew in the vicinity of the lake, and mean July air temperatures were similar to present-day ones between 7.9 and 7.0 kyr BP. The warmest and driest climate occurred at 7.0-5.0 kyr BP. At that time, the region had open steppe landscapes; birch groves began to spread. A cooling trend is seen after 5.5 kyr BP, when forest-steppe began to emerge. Steppe communities started to dominate again after 1.5 kyr BP. Mean July air temperatures lower than now are reconstructed for the period of 1.9-1 kyr BP, and then the temperatures became similar to present-day ones. Comparing the archaeological data on the types of economy of the population which inhabited the Baraba forest-steppe with the data on changes in the natural environment revealed a connection between the gradual transition from hunting and fishing to livestock breeding and the development of forest-steppe landscapes with a decrease in the area covered by forests. The development of the forest-steppe as an ecotonic landscape starting around 5 kyr BP might have contributed to the coexistence of several archaeological cultures with different types of economy on the same territory. (C) 2017 Elsevier Ltd. All rights reserved.
EnGeoMAP 2.0
(2017)
Algorithms for a rapid analysis of hyperspectral data are becoming more and more important with planned next generation spaceborne hyperspectral missions such as the Environmental Mapping and Analysis Program (EnMAP) and the Japanese Hyperspectral Imager Suite (HISUI), together with an ever growing pool of hyperspectral airborne data. The here presented EnGeoMAP 2.0 algorithm is an automated system for material characterization from imaging spectroscopy data, which builds on the theoretical framework of the Tetracorder and MICA (Material Identification and Characterization Algorithm) of the United States Geological Survey and of EnGeoMAP 1.0 from 2013. EnGeoMAP 2.0 includes automated absorption feature extraction, spatio-spectral gradient calculation and mineral anomaly detection. The usage of EnGeoMAP 2.0 is demonstrated at the mineral deposit sites of Rodalquilar (SE-Spain) and Haib River (S-Namibia) using HyMAP and simulated EnMAP data. Results from Hyperion data are presented as supplementary information.
Understanding evolution and ecology of endemic plants is of great importance for conservation of those rare and endangered species. Pairwise comparisons of plant functional traits could be an adequate method to get insights in evolutionary and ecological processes. We examined whether morphological traits representing competitive ability and habitat specificity differ between endemics and common plants. Therefore, we performed pairwise comparison analyses of 9 plant functional traits in 36 congeneric pairs of endemics and their common congeners on the East Mediterranean island of Cyprus, i.e., the first such study conducted on a Mediterranean island. We found that endemic species prefer higher elevations and more extreme habitats. Endemics were smaller and they had smaller flowers than their common congeners. Common species had higher chromosome numbers than endemic ones. Endemic and common species showed no significant differences in canopy height, inflorescence height, leaf length and width, and flowering period. Our study showed that the situation on a large oceanic island does not differ from results in mainland research areas.
Soil properties show high heterogeneity at different spatial scales and their correct characterization remains a crucial challenge over large areas. The aim of the study is to quantify the impact of different types of uncertainties that arise from the unresolved soil spatial variability on simulated hydrological states and fluxes. Three perturbation methods are presented for the characterization of uncertainties in soil properties. The methods are applied on the soil map of the upper Neckar catchment (Germany), as an example. The uncertainties are propagated through the distributed mesoscale hydrological model (mHM) to assess the impact on the simulated states and fluxes. The model outputs are analysed by aggregating the results at different spatial and temporal scales. These results show that the impact of the different uncertainties introduced in the original soil map is equivalent when the simulated model outputs are analysed at the model grid resolution (i.e. 500 m). However, several differences are identified by aggregating states and fluxes at different spatial scales (by subcatchments of different sizes or coarsening the grid resolution). Streamflow is only sensitive to the perturbation of long spatial structures while distributed states and fluxes (e.g. soil moisture and groundwater recharge) are only sensitive to the local noise introduced to the original soil properties. A clear identification of the temporal and spatial scale for which finer-resolution soil information is (or is not) relevant is unlikely to be universal. However, the comparison of the impacts on the different hydrological components can be used to prioritize the model improvements in specific applications, either by collecting new measurements or by calibration and data assimilation approaches. In conclusion, the study underlines the importance of a correct characterization of uncertainty in soil properties. With that, soil maps with additional information regarding the unresolved soil spatial variability would provide strong support to hydrological modelling applications.