TY - THES A1 - Maghsoudi, Samira T1 - Spatiotemporal microseismicity patterns and detection performance in mining environments Y1 - 2014 CY - Potsdam ER - TY - JOUR A1 - Wang, Y. A1 - Herzschuh, Ulrike A1 - Shumilovskikh, L. S. A1 - Mischke, Steffen A1 - Birks, H. John B. A1 - Wischnewski, J. A1 - Böhner, Jürgen A1 - Schluetz, F. A1 - Lehmkuhl, F. A1 - Diekmann, Bernhard A1 - Wuennemann, B. A1 - Zhang, C. T1 - Open Access Quantitative reconstruction of precipitation changes on the NE Tibetan Plateau since the Last Glacial Maximum - extending the concept of pollen source area to pollen-based climate reconstructions from large lakes JF - Climate of the past : an interactive open access journal of the European Geosciences Union N2 - Pollen records from large lakes have been used for quantitative palaeoclimate reconstruction, but the influences that lake size (as a result of species-specific variations in pollen dispersal patterns that smaller pollen grains are more easily transported to lake centre) and taphonomy have on these climatic signals have not previously been systematically investigated. We introduce the concept of pollen source area to pollen-based climate calibration using the north-eastern Tibetan Plateau as our study area. We present a pollen data set collected from large lakes in the arid to semi-arid region of central Asia. The influences that lake size and the inferred pollen source areas have on pollen compositions have been investigated through comparisons with pollen assemblages in neighbouring lakes of various sizes. Modern pollen samples collected from different parts of Lake Donggi Cona (in the north-eastern part of the Tibetan Plateau) reveal variations in pollen assemblages within this large lake, which are interpreted in terms of the species-specific dispersal and depositional patterns for different types of pollen, and in terms of fluvial input components. We have estimated the pollen source area for each lake individually and used this information to infer modern climate data with which to then develop a modern calibration data set, using both the multivariate regression tree (MRT) and weighted-averaging partial least squares (WA-PLS) approaches. Fossil pollen data from Lake Donggi Cona have been used to reconstruct the climate history of the north-eastern part of the Tibetan Plateau since the Last Glacial Maximum (LGM). The meanannual precipitation was quantitatively reconstructed using WA-PLS: extremely dry conditions are found to have dominated the LGM, with annual precipitation of around 100 mm, which is only 32% of present-day precipitation. A gradually increasing trend in moisture conditions during the Late Glacial is terminated by an abrupt reversion to a dry phase that lasts for about 1000 yr and coincides with "Heinrich event 1" in the North Atlantic region. Subsequent periods corresponding to the Bolling/Allerod interstadial, with annual precipitation (P-ann) of about 350 mm, and the Younger Dryas event (about 270 mm P-ann) are followed by moist conditions in the early Holocene, with annual precipitation of up to 400 mm. A drier trend after 9 cal. ka BP is followed by a second wet phase in the middle Holocene, lasting until 4.5 cal. ka BP. Relatively steady conditions with only slight fluctuations then dominate the late Holocene, resulting in the present climatic conditions. The climate changes since the LGM have been primarily driven by deglaciation and fluctuations in the intensity of the Asian summer monsoon that resulted from changes in the Northern Hemisphere summer solar insolation, as well as from changes in the North Atlantic climate through variations in the circulation patterns and intensity of the westerlies. Y1 - 2014 U6 - https://doi.org/10.5194/cp-10-21-2014 SN - 1814-9324 SN - 1814-9332 VL - 10 IS - 1 SP - 21 EP - 39 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Dietze, Elisabeth A1 - Maussion, F. A1 - Ahlborn, M. A1 - Diekmann, Bernhard A1 - Hartmann, K. A1 - Henkel, K. A1 - Kasper, T. A1 - Lockot, G. A1 - Opitz, S. A1 - Haberzettl, T. T1 - Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments JF - Climate of the past : an interactive open access journal of the European Geosciences Union N2 - Grain-size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy, this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain-size end-member modelling analysis. Between three and five robust grain-size end-member subpopulations were distinguished at different sites from similarly-likely end-member model runs. Their main modes were grouped and linked to common sediment transport and depositional processes that can be associated with contemporary Tibetan climate (precipitation patterns and lake ice phenology, gridded wind and shear stress data from the High Asia Reanalysis) and local catchment configurations. The coarse sands and clays with grain-size modes > 250 mu m and < 2 mu m were probably transported by fluvial processes. Aeolian sands (similar to 200 mu m) and coarse local dust (similar to 60 mu m), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes similar to 25 mu m may derive from near-by sources that keep in longer term suspension. The continuous background dust is differentiated into two robust end members (modes: 5-10 and 2-5 mu m) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upper-level westerly and episodic northerly wind transport. According to this study grain-size end members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19 +/- 5%), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 +/- 14% and 51 +/- 11%). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be cross-checked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history. Y1 - 2014 U6 - https://doi.org/10.5194/cp-10-91-2014 SN - 1814-9324 SN - 1814-9332 VL - 10 IS - 1 SP - 91 EP - 106 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Aich, Valentin A1 - Liersch, Stefan A1 - Vetter, T. A1 - Huang, S. A1 - Tecklenburg, J. A1 - Hoffmann, P. A1 - Koch, H. A1 - Fournet, S. A1 - Krysanova, Valentina A1 - Mueller, N. A1 - Hattermann, Fred Fokko T1 - Comparing impacts of climate change on streamflow in four large African river basins JF - Hydrology and earth system sciences : HESS N2 - This study aims to compare impacts of climate change on streamflow in four large representative African river basins: the Niger, the Upper Blue Nile, the Oubangui and the Limpopo. We set up the eco-hydrological model SWIM (Soil and Water Integrated Model) for all four basins individually. The validation of the models for four basins shows results from adequate to very good, depending on the quality and availability of input and calibration data. For the climate impact assessment, we drive the model with outputs of five bias corrected Earth system models of Coupled Model Intercomparison Project Phase 5 (CMIP5) for the representative concentration pathways (RCPs) 2.6 and 8.5. This climate input is put into the context of climate trends of the whole African continent and compared to a CMIP5 ensemble of 19 models in order to test their representativeness. Subsequently, we compare the trends in mean discharges, seasonality and hydrological extremes in the 21st century. The uncertainty of results for all basins is high. Still, climate change impact is clearly visible for mean discharges but also for extremes in high and low flows. The uncertainty of the projections is the lowest in the Upper Blue Nile, where an increase in streamflow is most likely. In the Niger and the Limpopo basins, the magnitude of trends in both directions is high and has a wide range of uncertainty. In the Oubangui, impacts are the least significant. Our results confirm partly the findings of previous continental impact analyses for Africa. However, contradictory to these studies we find a tendency for increased streamflows in three of the four basins (not for the Oubangui). Guided by these results, we argue for attention to the possible risks of increasing high flows in the face of the dominant water scarcity in Africa. In conclusion, the study shows that impact intercomparisons have added value to the adaptation discussion and may be used for setting up adaptation plans in the context of a holistic approach. Y1 - 2014 U6 - https://doi.org/10.5194/hess-18-1305-2014 SN - 1027-5606 SN - 1607-7938 VL - 18 IS - 4 SP - 1305 EP - 1321 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Kneis, David A1 - Chatterjee, C. A1 - Singh, R. T1 - Evaluation of TRMM rainfall estimates over a large Indian river basin (Mahanadi) JF - Hydrology and earth system sciences : HESS N2 - The paper examines the quality of satellite-abased precipitation estimates for the lower Mahanadi River basin (eastern India). The considered data sets known as 3B42 and 3B42-RT (version 7/7A) are routinely produced by the tropical rainfall measuring mission (TRMM) from passive microwave and infrared recordings. While the 3B42-RT data are disseminated in real time, the gauge-aadjusted 3B42 data set is published with a delay of some months. The quality of the two products was assessed in a two-astep procedure. First, the correspondence between the remotely sensed precipitation rates and rain gauge data was evaluated at the subbasin scale. Second, the quality of the rainfall estimates was assessed by analysing their performance in the context of rainfall-arunoff simulation. At sub-abasin level (4000 to 16 000 km(2)) the satellite-abased areal precipitation estimates were found to be moderately correlated with the gauge-abased counterparts (R-2 of 0.64-0.74 for 3B42 and 0.59-0.72 for 3B42-RT). Significant discrepancies between TRMM data and ground observations were identified at high-aintensity levels. The rainfall depth derived from rain gauge data is often not reflected by the TRMM estimates (hit rate < 0.6 for ground-abased intensities > 80 mm day(-1)). At the same time, the remotely sensed rainfall rates frequently exceed the gauge-abased equivalents (false alarm ratios of 0.2-0.6). In addition, the real-atime product 3B42-RT was found to suffer from a spatially consistent negative bias. Since the regionalisation of rain gauge data is potentially associated with a number of errors, the above results are subject to uncertainty. Hence, a validation against independent information, such as stream flow, was essential. In this case study, the outcome of rainfall-arunoff simulation experiments was consistent with the above-mentioned findings. The best fit between observed and simulated stream flow was obtained if rain gauge data were used as model input (Nash-Sutcliffe index of 0.76-0.88 at gauges not affected by reservoir operation). This compares to the values of 0.71-0.78 for the gauge-djusted TRMM 3B42 data and 0.65-0.77 for the 3B42-RT real-atime data. Whether the 3B42-RT data are useful in the context of operational runoff prediction in spite of the identified problems remains a question for further research. Y1 - 2014 U6 - https://doi.org/10.5194/hess-18-2493-2014 SN - 1027-5606 SN - 1607-7938 VL - 18 IS - 7 SP - 2493 EP - 2502 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Nussbaumer, S. A1 - Schaub, Y. A1 - Huggel, C. A1 - Walz, Ariane T1 - Risk estimation for future glacier lake outburst floods based on local land-use changes JF - Natural hazards and earth system sciences N2 - Effects of climate change are particularly strong in high-mountain regions. Most visibly, glaciers are shrinking at a rapid pace, and as a consequence, glacier lakes are forming or growing. At the same time the stability of mountain slopes is reduced by glacier retreat, permafrost thaw and other factors, resulting in an increasing landslide hazard which can potentially impact lakes and therewith trigger far-reaching and devastating outburst floods. To manage risks from existing or future lakes, strategies need to be developed to plan in time for adequate risk reduction measures at a local level. However, methods to assess risks from future lake outbursts are not available and need to be developed to evaluate both future hazard and future damage potential. Here a method is presented to estimate future risks related to glacier lake outbursts for a local site in southern Switzerland (Naters, Valais). To generate two hazard scenarios, glacier shrinkage and lake formation modelling was applied, combined with simple flood modelling and field work. Furthermore, a land-use model was developed to quantify and allocate land-use changes based on local-to-regional storylines and three scenarios of land-use driving forces. Results are conceptualized in a matrix of three land-use and two hazard scenarios for the year 2045, and show the distribution of risk in the community of Naters, including high and very high risk areas. The study underlines the importance of combined risk management strategies focusing on land-use planning, on vulnerability reduction, as well as on structural measures (where necessary) to effectively reduce future risks related to lake outburst floods. Y1 - 2014 U6 - https://doi.org/10.5194/nhess-14-1611-2014 SN - 1561-8633 VL - 14 IS - 6 SP - 1611 EP - 1624 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Menges, Johanna A1 - Huguet, C. A1 - Alcaniz, Josep M. A1 - Fietz, Susanne A1 - Sachse, Dirk A1 - Rosell-Mele, A. T1 - Influence of water availability in the distributions of branched glycerol dialkyl glycerol tetraether in soils of the Iberian Peninsula JF - Biogeosciences Y1 - 2014 U6 - https://doi.org/10.5194/bg-11-2571-2014 SN - 1726-4170 SN - 1726-4189 VL - 11 IS - 10 SP - 2571 EP - 2581 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Dulanya, Zuze A1 - Croudace, Ian A1 - Reed, Jane M. A1 - Trauth, Martin H. T1 - Palaeolimnological reconstruction of recent environmental change in Lake Malombe (S. Malawi) using multiple proxies JF - Water SA N2 - Shallow inland water bodies in Malawi continue to be threatened by various environmental challenges despite their importance to the fisheries industry. Due to the complex interaction between natural and anthropogenic disturbances, disentangling the effect of the two may be a complicated process. The littoral zone of most water bodies is important in environmental reconstructions including pollution and lake level monitoring. This study used a littoral zone, transect-based approach employing multi-proxy palaeolimnological techniques to reconstruct recent environmental change (ca. 100 yrs.) in Lake Malombe in the Malawi Rift, East Africa. The results of the study could inform fisheries management in Lake Malombe, which experienced a catastrophic decline in fish stocks. Results support documentary evidence for the complete desiccation of the lake less than 100 years ago. Subsequently, there is evidence for accelerated eutrophication in the recent past. In light of these results, it is concluded that transect sampling approaches rather than relying on single core measurements, and the need for careful consideration of the types of proxy, are significant considerations in palaeoenvironmental reconstructions. KW - littoral zone KW - palaeolimnology KW - diatoms KW - Lake Malombe Y1 - 2014 U6 - https://doi.org/10.4314/wsa.v40i4.17 SN - 0378-4738 SN - 1816-7950 VL - 40 IS - 4 SP - 717 EP - 727 PB - Water Research Commission CY - Pretoria ER - TY - JOUR A1 - Schwanghart, Wolfgang A1 - Scherler, Dirk T1 - Short Communication: TopoToolbox 2-MATLAB-based software for topographic analysis and modeling in Earth surface sciences JF - Earth surface dynamics N2 - TopoToolbox is a MATLAB program for the analysis of digital elevation models (DEMs). With the release of version 2, the software adopts an object-oriented programming (OOP) approach to work with gridded DEMs and derived data such as flow directions and stream networks. The introduction of a novel technique to store flow directions as topologically ordered vectors of indices enables calculation of flow-related attributes such as flow accumulation similar to 20 times faster than conventional algorithms while at the same time reducing memory overhead to 33% of that required by the previous version. Graphical user interfaces (GUIs) enable visual exploration and interaction with DEMs and derivatives and provide access to tools targeted at fluvial and tectonic geomorphologists. With its new release, TopoToolbox has become a more memory-efficient and faster tool for basic and advanced digital terrain analysis that can be used as a framework for building hydrological and geomorphological models in MATLAB. Y1 - 2014 U6 - https://doi.org/10.5194/esurf-2-1-2014 SN - 2196-6311 SN - 2196-632X VL - 2 IS - 1 SP - 1 EP - 7 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Reiter, Karsten A1 - Heidbach, Oliver T1 - 3-D geomechanical-numerical model of the contemporary crustal stress state in the Alberta Basin (Canada) JF - Solid earth N2 - In the context of examining the potential usage of safe and sustainable geothermal energy in the Alberta Basin, whether in deep sediments or crystalline rock, the understanding of the in situ stress state is crucial. It is a key challenge to estimate the 3-D stress state at an arbitrarily chosen point in the crust, based on sparsely distributed in situ stress data. To address this challenge, we present a large-scale 3-D geomechanical-numerical model (700 km x 1200 km x 80 km) from a large portion of the Alberta Basin, to provide a 3-D continuous quantification of the contemporary stress orientations and stress magnitudes. To calibrate the model, we use a large database of in situ stress orientation (321 S-Hmax) as well as stress magnitude data (981 S-V, 1720 S-hmin and 2 (+11) S-Hmax) from the Alberta Basin. To find the best-fit model, we vary the material properties and primarily the displacement boundary conditions of the model. This study focusses in detail on the statistical calibration procedure, because of the large amount of available data, the diversity of data types, and the importance of the order of data tests. The best-fit model provides the total 3-D stress tensor for nearly the whole Alberta Basin, and allows estimation of stress orientation and stress magnitudes in advance of any well. First-order implications for the well design and configuration of enhanced geothermal systems are revealed. Systematic deviations of the modelled stress from the in situ data are found for stress orientations in the Peace River and the Bow Island Arch as well as for leak-off test magnitudes. Y1 - 2014 U6 - https://doi.org/10.5194/se-5-1123-2014 SN - 1869-9510 SN - 1869-9529 VL - 5 IS - 2 SP - 1123 EP - 1149 PB - Copernicus CY - Göttingen ER -