Research

The East African Rift and the Himalayan collision zone constitute two geodynamic end-member scenarios that provide rich opportunities to analyze the relationships between tectonic processes, the evolution of topography and atmospheric circulation patterns, as well as related changes in surface-process systems. Continental extension as a precursor to continental break-up dominates the East African Rift system from the Afar Depression to Mozambique and beyond. In this region sustained extension since Oligo-Miocene time has resulted in a mosaic of individual rift basins and intervening structural or volcanic highs that have provided a highly variable environment, which yields key information regarding the mechanistic principles of continental extension, magmatism, environmental change, mammalian and hominin evolution (Chorowicz, 2005; Trauth et al., 2005; Potts, 2007; Kingston, 2007). In contrast the effects of advanced continental collision characterize the arcuate Himalaya-Karakoram orogen, where protracted plate convergence and shortening have created the type section of collisional mountain and plateau building, which has caused climate change at global scale (e.g., Raymo et al., 1988; Kutzbach et al., 1989, Ruddiman and Kutzbach, 1991). Both areas continue to be tectonically active and fundamentally affect atmospheric circulation systems, and hence the spatiotemporal distribution of rainfall, erosion and depositional processes (e.g., Bookhagen and Burbank, 2006; Thiede et al., 2009; Hren et al., 2009; Van der Beek et al., 2009). Being located within a monsoonal climate, both regions are thus subjected to highly seasonal rainfall and amplification or weakening of the precipitation system, which has left important imprints in the landscape and in variety of geological archives. The unifying theme of this proposal is the challenging research area of tectonics-climate-biosphere interactions and Earth surface processes at different time and length scales.

Abridged version of doctoral research projects

[1] Strecker, Bookhagen, Oberhänsli, Thiede – Reconstructing rates and impact of glacial erosion in the Arun Valley, eastern Himalaya. The evolution of the topography of mountain belts results from the interplay of constructive (tectonic) and destructive (erosive) forces related to fluvial, hillslope, and glacial erosion processes. Most studies in the past have ignored the single, probably most efficient erosion agent: glaciers. Their role in shaping the morphology of orogens remains poorly documented and is likely to be highly variable through time. The aim of this project is to determine rates of glacial erosion processes and rate changes through time focusing on the following questions (1) How do rates of erosion in a glaciated orogen vary at glacial-interglacial time scales? [field study/laboratory work/data generation]. Previous glacial deposits will be studied using sedimentary and geochemical methods [cosmogenic nuclides, εNd (distinguish between Lesser and Tethyan/Greater Himalaya), 87Sr/86Sr (distinguish between Greater/Lesser and Tethyan Himalaya, OSL and CRN dating] These short-term rates will be compared with long-term exhumation rates in glaciated and non-glaciated areas (thermochronology project [2]). (2) What are the driving forces of glaciation in the central and eastern Himalaya? [modeling]. Several glaciers will be compared along a N-S transect. Is the glacial extent controlled by (a) Monsoonal-moisture transport, the (b) winter westerlies, (c) solar radiation or (d) local topographic effects that may prevent further generalizations. The Arun Valley of the central Himalaya lends itself to such a three-tiered study. Similar to the Sutlej Valley in the NW sector of the orogen, the Arun Valley provides a natural transect through all Himalayan geologic units and thus constitutes an excellent environment for using geochemical tracer methods to quantify erosion. In addition, the valley is located near the beginning of the monsoonal conveyer belt and receives twice as much annual rainfall than the western regions previously studied in GRK projects. This will thus allow comparisons of erosional efficiency and glacial processes with climatic threshold regions that are located at the far, western end of the Indian Summer Monsoon system. A rigorous analysis of both environments will therefore clarify the erosional contributions of westerly and monsoon-related moisture sources, respectively. The study will generate synergistic effects at various levels and benefit from close collaboration with ongoing climate modeling studies (Dethloff), low-medium temperature thermochronologic and thermal modeling studies (Bookhagen, Sobel, O’Brien) and paleoenvironmental assessments based on the analysis of lacustrine sediments in high-elevation sectors of the orogen (Brauer, Prasad, Herzschuh).

[2] O'Brien, Scherler, Sobel, Sudo, Thiede – Differentiating between tectonic and erosional exhumation in the Eastern Nepalese Himalaya. In the Himalaya of eastern Nepal, between the Everest and Kangchenjunga regions, the Greater (GHS) and Lesser Himalayan Sequences (LHS) have been folded by both N-S and E-W –trending structures. This pattern has locally produced the Arun and Tamor tectonic windows, which allow efficient access to an extended structural sequence, above and below the Main Central Thrust (MCT). In general, the MCT was active during the early-Middle Miocene as documented by published Ar/Ar ages in the GHS. However, in many parts of the range, apatite fission track ages of around 1-2 Ma show much younger late-stage exhumation in the high Himalaya. In contrast, in the structurally deeper LHS, AFT ages are significantly older (12-18 Ma) than in the GHS. This counter-intuitive result suggests that the thermal history is not a straightforward function of structural depth over time. In addition, these data suggest very little denudation in the northern LHS since the Middle Miocene. Linking low temperature thermochronologic data to exhumation rates requires a good knowledge of the evolution of the thermal structure: a complex problem in dynamic settings with transient perturbed geotherms such as in the Himalaya. To solve this problem will require high quality thermochronologic data (mica Ar/Ar, apatite and zircon U-Th/He and AFT dating) from a geologically well-defined area, combined with 3-D thermal modelling. The N-S structures in eastern Nepal have been interpreted as a product of enhanced extrusion guided by focused fluvial erosion. The implication is that the efficiency of glacial and fluvial erosion has caused significant isostatically-driven uplift. If this hypothesis is correct, the magnitude, rate and timing of cooling must vary along and across the range. Quantifying this concept is complicated by the changes in climate and hence precipitation which have occurred during the Cenozoic. For a reliable test, it is thus imperative to have a correct understanding of the thermal structure and it’s evolution during the Neogene as well as reliable paleo-climatic data. The proposed study area allows one to examine the hanging wall units above the MCT in several positions at varying distances from the topographic front of the Himalaya. By examining the evolution of the hanging wall at a series of positions perpendicular to the transport direction, one can better constrain the structural evolution. Since the modern climate also varies along this same transect, one can also examine the influence of varying erosional efficiencies on the same lithological sequence. The crystalline rocks of the MCT hanging wall contain mineral assemblages which are well suited for thermochronology. The structures themselves are amenable to direct dating using in-situ Ar/Ar dating as well as measurement and evaluation of Ar diffusion profiles in mica. The study area has been sufficiently well mapped so that the project can quickly move forward. This newly-won data will complement the emerging results from an ongoing American project in the adjacent Arun valley. Our project is tightly interwoven with the project of [1] on the determination of glacial erosion at 10^3-10^3 y timescales in the Arun valley.

[3] Thiede, Scherler, Codilean, Bookhagen, Korup, Strecker – Competing influence of fluvial and glacial erosion in the western Himalaya. The temporal and spatial distribution of erosion in the Himalaya has received considerable attention because of the important role erosion plays in the development of the range and, more generally, because of its potential feedback on tectonics. Many studies examined rates of fluvial incision and mass wasting over short and long time scales and linked these with the distribution and variability of monsoonal rainfall (e.g., Bookhagen et al., 2005a, b; Thiede et al., 2005, 2009). Little is known, however, about rates of erosion at the heavily glacierized crest of the range and there is no consensus on whether glaciers accelerate or impede erosion in these regions (e.g., Brozovic et al., 1997; Burbank et al., 2003; Korup and Montgomery, 2008). Part of this confusion appears to stem from temporally highly variable rates of glacial erosion (Koppes and Montgomery, 2009). The proposed study aims at determining glacial erosion rates over different time scales and at several glaciers spanning a steep gradient in precipitation in the neighboring Kullu and Chandra Valleys, western Himalaya. First, detrital low-temperature chronology data of river sediments just below the glacial terminus will provide average basin-wide erosion rates on Myr timescales. These can be compared with existing low-temperature chronology data from bedrock samples in the study areas (Thiede et al., 2009). Second, bedrock samples will be collected and used for optically stimulated luminescence (OSL) analysis. Application of the OSL technique as a very low-temperature chronometer is still under development but would provide cooling rate estimates over the last glacial cycle (Herman et al., 2008). Third, terrestrial cosmogenic nuclide (TCN) analysis of supra-glacial debris cover will be used to assess average headwall retreat rates over thousand-year time scales. This application of TCNs has been successfully employed in studies from Nepal (Heimsath et al., 2008), the Karakoram (Seong et al., 2008), and Alaska (Ward et al., 2008). Finally, in order to derive glacial erosion rates from the obtained data, modeling of the glaciers is required and will be done using an existing and available numerical glacier model (Kessler et al., 2006), calibrated using present-day glacier-surface velocities (Scherler et al., 2008). The comparison of erosion/exhumation rate estimates over different time scales and from glaciers situated in humid and arid parts of the orogen will elucidate the temporal and spatial variability of glacial erosion rates. The study is related to several projects [5], [8], [9], [11], [12] of the previous funding period and will closely interact with projects [1] and [2] of this proposal.

[4] Dethloff, Rinke –Aerosol-Cloud-Monsoon Interactions based on HIRHAM Regional Climate Model simulations from 1950 until 2010. Notable warming trends have been observed in the Arctic as discussed by Law and Stohl (2007). Although increased human-induced emissions of long-lived greenhouse gases are the main driving factor, air pollutants, such as aerosols and ozone, are also important. Black Carbons (BC) particles suspended in the atmosphere could result in complex radiative effects by acting as light absorber. BC deposited on snow and ice surfaces could absorb sunlight and reduce the albedo, thus potentially accelerating the melting of snow cover and sea ice. Glaciers and polar ice sheets are excellent archives for documenting constituents in the atmosphere. BC measurement by Ming et al. (2008) provided the first record of BC deposition during the past 50 yrs in the high Himalayas. An increasing trend of BC concentrations was revealed since the mid-1990s with higher concentrations in monsoon seasons than those in non-monsoon seasons. BC emitted from South Asia could penetrate into the Tibetan Plateau by leading to significant increasing trend of the radiative forcing with 4.5 Wm−2. BC concentrations in the atmosphere over the Himalayas and in the ice of glaciers could not be neglected when assessing the warming effects on glacier melting and water cycle in the Himalayas. The direct climate effect of aerosols has been studied by Rinke et al. (2004) within a regional atmospheric model of the Arctic. We will apply similar regional climate model simulations including the impacts of BC in a highly polluted area with increasing population over the Indian-Asian integration area, successfully analyzed in the past by Polanski et al. (2009). The suggested use of a high resolution regional atmospheric model covering the third pole region (Himalaya and India) is important for studying its regional climatic impacts due to atmospheric baroclinic circulation systems. The interaction among aerosols, clouds, and climate conditions is particularly complex in the Himalaya, because of the high surface albedo; the marked annual cycle of aerosol characteristics; the static stability of lower troposphere and the complex radiative interactions between aerosols, clouds, and snow. Lower tropospheric warming due to soot and BC particles over the land areas of India and Asia impacts cloud, radiation, atmospheric circulation and monsoon development. The regional climate model simulations over ca 60 years will be compared with new proxy records for these decades developed within Graduate School 1364. The project is linked to other projects associated with the most recent climate change, such as projects [5], [9] and [12]. Our project also plays an important role in bridging the gap between paleoclimate studies and current climate change.

[5] Jeltsch, Trauth, Tiedemann – Modeling past and future climate induced vegetation changes in East African savannas. The late Cenozoic climate of East Africa is punctuated by episodes of short, alternating periods of extreme wetness and aridity, superimposed on a regime of subdued moisture availability exhibiting a long-term drying trend (Trauth et al., 2007). These periods of extreme climate variability have been hypothesized to have provided a catalyst for evolutionary change and driven key speciation and dispersal events amongst mammals and hominins in East Africa (Trauth et al., 2005, 2007, 2009). Clearly, these changes were mediated by climate induced vegetation shifts from savanna woodland and forests under moist conditions to open savanna or even grassland in drier periods. Carbon isotope records from both soil carbonates (Levin et al., 2004; Wynn, 2004) and biomarkers (n-alkanes) extracted from deep-sea sediments (Feakins et al., 2005) provide clear evidence of a long-term vegetation shift from a dominance of woody species (C3 plants) to grasses (C4 plants) with increasing aridity during the Plio-Pleistocene (deMenocal, 2004; Trauth et al., 2009). Though, these and related studies indicate the principle change in vegetation composition and structure, it remains unclear how precisely vegetation trajectories were influenced by climate in the transient phases of wetter and more variable conditions. Savannas are typically described as non-equilibrium systems (e.g. Jeltsch et al., 2000) that are largely driven by climate, fire and herbivory. This includes crucial feedbacks between savanna vegetation, fire frequency and intensity, and the effects of grazers and browsers (Jeltsch et al., 1996, 1998, 1999; Tietjen et al., 2007, 2009). Understanding the East African savanna vegetation response to episodes of short, alternating periods of extreme wetness and aridity during the late Cenozoic climate would thus require process-based modeling of vegetation dynamics including the dynamics of mentioned key drivers, i.e. climate, fire, and herbivory. Dynamic modeling will allow to produce vegetation scenarios that can be compared against existing paleoclimate records, such as paleo-lake levels (proxy for precipitation / evaporation ratios), diatoms (for hydrology and hydrochemistry, nutrients in lakes), pollen (for vegetation) and, charcoal (for fire) records. It will contribute to a better understanding of climate-environment coupling including buffering effects, non-linearities and system resilience. Understanding vegetation response under scenarios of late Cenozoic climate change at the level of driving mechanisms will further provide a suitable basis for modeling savanna vegetation changes under future climate change scenarios. Key objectives are: process-based, spatially explicit modeling of East African savanna vegetation transitions under scenarios of late Cenozoic climate changes; exploring transient vegetation dynamics including non-linearities, buffering mechanisms, fire-vegetation, herbivore-vegetation, and fire-herbivore-vegetation feedbacks; Using scenarios of late Cenozoic climate changes as a proxy for future climatic changes. Our key hypotheses are: (i) Dynamic process-based savanna models can explain vegetation changes in East African savanna systems under late Cenozoic climate fluctuations; (ii) Vegetation response to late Cenozoic climate fluctuations show nonlinear dynamics with buffering effects caused by vegetation-fire-herbivory feedbacks. (iii) Landscape-level transient dynamics is non-homogenous and strongly influenced by topography and dispersal processes. Synergies are expected through projects funded by other sources: More than 15 years of savanna research funded by different sources, including BIOTA Africa (BMBF, 2001-2010). A new interdisciplinary, multi-national savanna research project (Namibia, Botswana, South Africa) is under evaluation (BMBF); EU-project proposal in preparation. Our project is linked to other projects on African climate change, such as projects [6], [7], [9], [10], [14], [15], [16], [18] and [26].

[6] Kaufmann, Trauth –Climate-erosion-vegetation interaction using multispectral remote sensing data during the last few decades. East Africa faces extreme risk from climate change. For several years the failure of the long rains has led to dramatic situations with mega-droughts, water shortage and reduced harvests. On the other hand, extreme modes in the El Niño/Southern Oscillation and the Indian Ocean Dipole are blamed to drive extreme rain events across the region, leading to floods destroying crops and the generation of mudslides affecting infrastructure in East Africa. In collaboration with projects [5], [9], [14] and others we aim at understanding the relationship between spatio-temporal rainfall patterns from the Tropical Rainfall Measuring Mission (TRMM) and surface processes such as the availability of water including soil moisture, snow coverage, vegetation variations via chlorophyll content and erosion in selected regions in East Africa. By means of time series and change detection techniques of multispectral satellite image data in the visible and short wave infrared (SWIR) range, these surficial parameters can be accurately mapped for the last three decades. The study sites to be investigated include selected rift basins also studied by other projects of the graduate school such as the densely populated Naivasha and Nakuru-Elmenteita basins in the Central Kenya rift (project [9]), the sparsely populated Suguta Valley and adjacent areas in the semiarid northern part of Kenya (project [10]). These areas are characterized by extreme topographic gradients, complex drainage networks and diverse sedimentary processes. In addition to these rift environments, we will map the distribution of rainfall, vegetation and erosion on high mountain peaks as Mt. Kenya that will provide a sensitive natural laboratory for vertical shifts in the response of the environment to climate change. The ultimate goal of this project is to better understand the sensitivity and vulnerability of equatorial East Africa to past, present and future climate change.

[7] Holschneider, Trauth – Detecting trends, rhythms and events in modern and past climate records using advanced methods of time-series analysis. Systematic efforts have addressed the key question of why hominin evolution has occurred in a pulsed pattern, with well-defined periods of extensive speciation or extinction, cultural change and geographic expansion, interspersed with long periods when relatively little change seems to occur. Here, we propose the analysis of existing marine and terrestrial records of past environmental changes during the Cenozoic to detect trends, rhythms and events in East African climate. Our tools employed here include linear and nonlinear methods in time-series and regression analysis to detect such changes in these datasets. We will concentrate on change points, abrupt transitions, changes in the variance and in the cyclicities. In particular Bayesian methods will provide the statistical background for hypothesis testing to retrieve the most likely inferred underlying model and to quantify confidence limits by opposing the assumed real model to other possible scenarios. In a first step simplified heteroscedastic model assumptions are made. We will consider a two slope behavior of the local variance. In this context a full exploration of the parameter space is possible and allows a global computation of the Bayesian posterior and marginal distributions. In a second step we will consider semi-parametric and non-parametric models for the local variability of the time series. In this description the change points appear simply as transition point between two regimes in the time series, which are controlled by different correlation length and/or sharp transition in the local variability. In this setting, the relevant posterior information can be obtained by Monte Carlo integration only, since a full exploration of the phase-space becomes unfeasible. This study links projects on generating paleo-environmental time series on all scales, such as projects [9], [10], [18], [21] and [28] with modeling projects such as project [4] and [5], but also with the project [15] on complex networks. The techniques developed will be mainly applied to time series coming from the data-generating projects, but also from established literature sources. The methodological development, however, will be useful for many other questions concerning the characterization and localization of transition points.

[8] Prasad, Helle, Wilkes, Sachse – A multiproxy, multi-archive approach to understand NE and SW monsoon variability in South India. The Indian monsoon has becomes synonymous with the SW summer monsoon. While it is true that most of the Indian subcontinent receives precipitation during the summer season, NE monsoon is also responsible for bringing rainfall to parts of southern India which are important source of water in this region of scare water resources. Till date very few studies have addressed the question of past variability in the NE monsoon, or documented regional variations in the relative contributions of the two precipitation regimes. We aim to reconstruct past climate variability in southern India using peat and runoff reservoirs. A spatiotemporal reconstruction on a regional/peninsular scale will help in understanding monsoonal, environmental, and possible human impact processes that operated during the Holocene. The concentration of pollen and organic matter is more in peat than in reservoir sediments. However, it is now established that enough pollen can be extracted from reservoir sediments for a meaningful palynological reconstruction. We aim to undertake a multi-proxy approach including (i) isotope investigations on cellulose extracted from the peat and modern vegetation, (ii) sedimentology and mineralogy of the inorganic component from the peat and reservoir sediments, (iii) biomarker approach reconstruct past changes in rainfall variability from the SW and NE monsoons in selected intervals. The proposed sites are in the Nilgiris (known age of some of these peat deposits is ~ 30-40 ka BP), Palnis (unexplored), and reservoirs from Karnataka and Tamil Nadu known age > ca. 2 ka). The project is linked to other paleoclimate projects, such as projects [12] and [13], but also provides important data for projects on climate and erosion, such as projects [1], [2] and [3].

[9] Tiedemann, Epp, Stoof, Trauth –Regionally synchronized or locally specific? Comparative historical genetics on organismic responses to environmental change among lakes in the East African Rift Valley. Today, the lakes in the East African Rift Valley range in alkalinity from pH 11 (Lake Elmenteita) to pH 8 (Lake Naivasha), and in depth from less than one meter to 15 meters. Historically they have undergone a number of drastic changes in lake level and environmental conditions, both on geological timescales and during the last centuries. Within this setting, we have established molecular genetic methods to study DNA from recent and historic lake sediments, focusing on rotifers and diatoms. We developed a protocol using taxon-specific polymerase chain reactions and separation of products by denaturing high performance liquid chromatography (DHPLC). As a proof-of-principle, we were able to analyze population and species succession in rotifers in the alkaline-saline crater lake Sonachi since the beginning of the 19th century. Populations were dominated by a single mitochondrial haplotype for a period of 150 years, and two putatively intraspecific turnovers in dominance occurred. They were both correlated to major environmental changes documented by profound visible changes in sediment composition of the core: the deposition of a volcanic ash and a historical lake level lowstand. The specific aim of this new proposal is to systematically exploit the potential of our newly established methods at the interface of geology and biosciences. Specifically, we will take three short sediment drill cores of each of the lakes. These will be sampled in increments of 2 cm, spanning from the recent surface sediment down to sediments several hundred years of age. Dating will be performed by 210Pb analysis. Sediments will be screened for Brachionus rotifers and diatoms following our aforementioned new molecular protocols to reveal population/species turnover or persistence, relative to changes in environmental conditions. Our symmetric hierarchical sampling scheme will allow for an assessment of within lake variation relative to the differences among lakes. This will enable us to reveal, whether environmental changes have a synchronized effect on all Rift lakes (despite of their different ecological conditions) or whether these effects are specific for single lake settings. This will give us a comprehensive picture of the influence of geologic/climatologic perturbations on limnic organisms and will further contribute to the establishment of historical genetics as a new proxy in geobiological research. The project is linked to other projects the most recent climate change, such as projects [6], [12] and [14].

[10] Trauth, Bergner, Jeltsch, Deino, Maslin, Olago, Odada – The Mid Pleistocene revolution in Eastern Africa (1.2-0.7 Ma) and its consequences for the evolution of Homo erectus and H. sapiens. Fieldwork in the East African Rift System by the proponents suggests there may have three protracted wet periods in the Rift Valley: 2.7-2.5 Ma, 1.9-1.7 Ma, and 1.1-0.9 Ma before present which seem to correlate with key stages in hominin evolution. Of particular interest for testing hypotheses of tectonics-climate-evolution linkages is the latest of these wet periods as it seems to be characterized by a very dynamic setting with extreme hydrological changes, dramatic vegetation variations, occurrence of abundant Acheulean stone tools in so-called handaxe factories suggesting larger populations of Homo erectus, significant migration tendencies of H. erectus out of Africa, and the disappearance of robust Australopithecus lineages including the genus Paranthropus with larger jaws, extreme cranial musculature that allows the evolution of larger cranes and hence larger brains. The Mid Pleistocene African revolution has lead to the evolution of H. sapiens that systematically developed sophisticated tools, was socially networked at an extreme level through the development of speech and language, and densely populated the world during the last 100 kyrs. This project aims at testing the hypothesis that important wet-dry-wet cycles provided a catalyst for these major events in hominin evolution and cultural innovations by means of correlating environmental fluctuations recorded in fluvio-lacustrine sequences along a North-South transect from Ethiopia to Southern Kenya. The study sites are Kariandusi (Central Kenya Rift), the Suguta Valley (Northern Kenya Rift), Baringo (Central/Northern Kenya Rift) and Chew Bahir (Southern Ethiopian Rift), whereas other well-studied Mid Pleistocene sites such as Olorgesailie (Southern Kenya Rift) and Melka Kunture (Central Ethiopian Rift) will be considered through existing collaborations. This project is largely financed through a funded DFG grant for fieldwork in the Suguta Valley. It is also linked with the ICDP "Hominid Sites and Paleolakes Drilling Project" initiative led by A. Cohen. A proposal on the Chew Bahir basin has also been submitted to the DFG ICDP-SPP program. The project is linked to other projects African climate change, such as projects [14] and [18], the remote sensing project [6], and also provides data for the modeling and data-analysis projects [5], [7] and [16].

[11] von Blanckenburg, Scherler, Dixon, Hewawasam – Causes for slow weathering and erosion in the steep, warm, monsun-subjected highlands of Sri Lanka. The Indian ocean island of Sri Lanka features in the centre a steep (mean slope =20°), high (up to 2500 m), warm (mean annual temperature = 20°C) and wet (two monsoon seasons with mean annual precipitation of up to 5000 mm/yr) mountain range. Measurements of cosmogenic nuclides in river sediment has resulted in surprisingly low pre-development erosion rates of only 5-30mm/ky. These are amongst the lowest measured for any mountain belt worldwide. This observation presents a paradox that has puzzled geomorphologists since its first finding. Key to this paradox might be the thick clay layers that cover Sri Lankan slopes and that are present were bedrock is not exposed. These saprolites are extremely weathered. Weathering is supply-limited which means that no new material is moved into the reactor such that no further weathering can take place. Hence new soil that could be eroded is not produced, and erosion rates are low. On the other hand, because erosion rates are so low no new soil is produced. This is a problem of substantial circularity. The cause could be the absence of tectonically driven landscape rejuvenation or the thick plant cover. We suggest to employ an analysis of the state of weathering, geomorphology and soil mineralogy to decipher the protective role of these saprolites. Furthermore, we suggest to investigate the role of higher plants, in particular those of the thick rain forest, as potential reducers of erosion or the enhancer of weathering. Standard tools shall be GIS analysis of landforms, cosmogenic 10Be as erosion rate meter, and the bulk chemical analysis of soils and bedrock. At the centerpiece of this proposal, however, are "non-traditional" stable isotopes that are calibrated and used as fingerprints of weathering and metal transfer through plants. The combination of this expertise is unique and now possible at Potsdam. The study presents an end member case for tectonically inactive shield regions. These can serve as a benchmark against which the fast erosion rate in active mountain belts of the Asian and African monsoon areas can be tested. The project is linked to other projects on tectonics, climate and erosion, such as projects [1], [2] and [3].

[12] Sachse, Bookhagen, Herzschuh – Deciphering the past and present monsoonal moisture gradients in the Arun valley, eastern Nepal. The proposed project aims to understand the importance of the past (ca. 15.000 y) and present-day seasonal moisture and environmental gradients in the Arun valley, eastern Nepal. The Arun valley is characterized by a very steep gradient in temperature and rainfall, caused by the action of the Indian monsoon. Any past change in the extent of this gradient therefore provides a proxy for the strength of the monsoonal system itself. Focus of this work is: (1) to delineate and quantify the strong climatic contrasts and their representation in the modern hydrology, vegetation and deposited biomass (in soils and sediments), (2) to identify its influence on the modern erosion and sediment fluxes, (3) to decipher the changes of the seasonal contrast and its impact on the past environment (with special respect to erosional changes) throughout the Late Pleistocene and Holocene. Our highly interdisciplinary approach is 4-fold: (1) to identify present-day seasonal climate (precipitation + temperature) gradient and annual vegetation course using remote-sensing and ground-based measurements, (2) to develop transfer functions of how organic geochemical, compound-specific stable isotope (hydrogen and carbon) data (and pollen data, PhD student in project [13], Herzschuh et al.) track the present-day hydrological and environmental gradient, (3) to date paleo-deposits using terrestrial cosmogenic nuclides, derive soil-production rates, and determine basin-wide erosion rates for the past and present, (4) to apply the developed transfer functions for organic geochemical biomarker stable isotope records (and pollen records derived from project [13]) on sedimentary deposits (lake sediments, for instance Chola Tso (see also following project [13]), paleosoils) and reconstruct the timing and extent of past changes in the climatic gradient.

[13] Herzschuh, Sachse, Bookhagen, Diekmann – Himalayan pollen as tracer of monsoonal strength and moisture source. Pollen grains are transported with monsoonal air currents and are rained out with precipitation being especially strong at the southern flank of the Himalaya. Hence pollen concentration and composition from upper Himalayan lake sediments - where no local pollen input occurs - is primary a signal of the moisture source. Millennial scale pollen records from such a lake were convincingly interpreted in that context. However, neither the relationship between air currents and modern pollen spectra has been proven statistically nor has such knowledge been used for the reconstruction of monsoonal changes on decadal and centennial time scales. Within the proposed PhD project we will strive to validate the following hypotheses: (1) Airborne pollen in the upper Himalaya is a measure of monsoonal circulation pattern and precipitation intensity from seasonal to centennial scale. (2) Circulation pattern and monsoonal strength changed in the course of global warming. The working program comprises the following aspects: (a) Analyses of daily pollen signal of one year collected with an airborne pollen trap located in the upper Arun valley and it numerical relation to meteorological information and circulation pattern. (b) Analyses of sedimentary pollen signals from a lake core obtained from Chola Tso (upper Arun valley, 27.9°M, 86.8°E, 4518 m) covering the last several hundred years. The modern pollen-circulation transfer functions, derived from modern pollen spectra will be applied to the lake pollen record to quantitatively reconstruct moisture origin and monsoonal strength. The PhD students from this project and project [12] will both conduct work on the sediment core obtained from Chola Tso, as both proxies will provide a set of highly complementary information on past changes in vegetation structure and moisture availability.

[14] Kallmeyer, Sachse, Stroncik, Tiedemann – Biogeochemical adaptation to variable lake chemistry. The East African Rift System (EARS) hosts a large number of lakes that exhibit a diverse range of salinities and pH values. So far, biogeochemical processes have mainly been studied in the marine environment. Except for a few studies on lakes affected by extremely low pH values due to acid mine drainage, most investigations focused on freshwater lakes with low salinities and near neutral pH like Lake Baikal or alpine lakes. Biogeochemical processes in the upper few meters of the sediment column are usually driven by the degradation of organic carbon. However, most of these reactions are strongly dependent on the chemical composition of the overlying waters. For example, one of the most important compounds in the sedimentary nitrogen cycle is ammonium, which is in a pH dependent equilibrium with ammonia, a compound that is toxic for many microbes. At high pH levels ammonia is the most abundant species, therefore the microbes involved in the nitrogen cycle have to adapt to these conditions. Organic carbon mineralization proceeds with depth via a sequence of different electron acceptors , according to the energy that can be gained by the respective process. After all electron acceptors are depleted, methano-genesis and fermentation become the dominant processes. Both can be fuelled by and can produce many different carbon sources, from carbon dioxide to short-chain organic acids. It is unclear how the different pH levels affect these processes. Even over geologically short time spans of years to decades, lakes in the EARS experience dramatic shifts in their water budget and therefore their salinity and biota. Consequently, the sediment composition is highly diverse. The abundant volcanic eruptions in the area lead to the deposition of ash layers, which also add a contrasting lithology to the already diverse range of sediment types. The project aims to understand how the different lake water and pore water chemistry influences the biogeochemical processes in the diverse range sediments and vice versa. The project is linked to other projects climate-biosphere linkages, such as projects [5], [6], [9], [10] and [18].

[15] Marwan, Kurths, Trauth – Spatio-temporal analysis of rainfall anomaly patterns and extremes in the monsoonal region from the complex network perspective. In collaboration with the remote sensing project [6] and the biomarker project [12], we propose an interdisciplinary project on data analysis in order to study complex relationships in the spatio-temporal dynamics of the African-Asian climate. The main focus will lie on Indian Ocean sea-surface temperature (SST) variations, in particular the Indian Ocean Dipole (IOD). The variation of the IOD has a strong impact on the East African climate patterns and the Asian Monsoon. In the last few years, the IOD has moved eastwards, leading to speculations on reduced African rainfall. One aim is, therefore, to apply the complex network analysis in order to investigate the stability and the spatial variation of African rainfall patterns with respect to the variation of the IOD, which may be affected by the global climate change. A second focus lies on the spatio-temporal analysis of extremes in rainfall data by means of complex networks. The network approach is a suitable and rather easy way to unveil small- and large-scale spatial patterns of extreme rainfall events (e.g. links between extreme events in Himalaya and East Africa regions). For the investigation, complex networks of the monsoonal climate system will be reconstructed using satellite (TRMM) rainfall data, SST data from the Indian Ocean, aggregated regional climate proxies as well as topographic and index data (El Niño/Southern Oscillation index SOI, Nino3, Indian Ocean Dipole Index DMI). The challenging methodological task is the integration of different kinds of regional and local data, such as TRMM rainfall data, scalar index series and topographical information. Another important problem is to estimate strength and directionality of time-varying connections between nodes and some sub-systems. Therefore, new approaches for network reconstruction will be developed, including alternative definitions for network links (e.g. by using recurrence and conditional probabilities). The structure of the networks will then be quantified and analysed in order to study relationships between different sub-systems (e.g. rainfall extremes and topography or variation of IOD), critical and dynamical properties as well as its temporal evolution. Historical and geological records from projects [10] and [12] will be used to compare present conditions with the past, to find analogous situations and to derive potential future pathways. This project will help to understand the mechanisms of the African climate variability due to IOD variation and Walker circulation, in particular whether an eastward shift of IOD (and Walker circulation) causes a decrease in African rainfall. Furthermore, this study will help answer questions on the spatial occurrence of rainfall extremes and their link to certain topographic conditions, even on large spatial scales/distances.

[16] Project not yet specified after the original project has been cancelled.

[17] Bousquet, Oberhänsli, Strecker, Wichura –Deep processes of plateau building East Africa. The interplay between the dominant denudation conditions and the rheology of the lithosphere, both well documented by erosion rates and processes can provide significant constraints on deep processes of plateau building. Processes that formed plateaus as the East African Plateau remain still debated. The East African rift system is generally described as a classic example of a continental rift, exhibiting characteristic patterns of rifting, volcanism and flanking uplifts (Ebinger and Sleep, 1998), but new investigations demonstrate that the plateau uplift pre-dates the rifting processes (Wichura et al., submitted). In many plateaus example, most of proposed models make predictions about the thickening, heating, and melting histories of the plateau, by tacking into account only crustal changes (flanking uplift due to mechanical relaxation of the crust (Ebinger et al., 1999); density change of the crust (Le Pichon et al., 1997, Hetenyi et al., 2006) or assuming removing of the lithospheric mantle due to plume activity as in East Africa or to mantle delamination (Tibet, Colorado). Recent studies on xenoliths and on seismic tomography show that beneath plateaus show strong variations in the lithospheric composition and structure. We propose to examine the contribution of mantle-crust interactions into plateau building for the East African plateau. The contribution of these interactions on plateau building will be estimated and quantified by the thermo-mechanical evolution of different uplift scenarios in light of changes in the physical properties of rocks. Property changes will be modeled using Gibb’s free energy minimization continuously during the geodynamic evolution. This project needs good constraints on earth surface processes as well as chemical composition and structure of the lower crust and of the lithospheric mantle. These are prerequisites to link surface processes with processes regarding the entire lithosphere. Close interaction to projects on rift structure, erosion control and climate evolution, such as project [20] will allow to better constrain the boundary conditions of the models.

[18] Trauth, Schäbitz –The Chew Bahir Coring Project: Climate-vegetation feedbacks during the African Humid Period in the southern Ethiopian Rift (DFG-SPP ICDP). We propose to obtain up to ten replicate ca. 15-20 meter long continuous sediment cores along a north-south and an east-west transect through the Chew Bahir basin, Southern Ethiopian Rift These cores presumably include the deposits of the African Humid Period (~15 to 5 kyrs BP) providing us with information about the last dry-wet-dry cycle and associated environmental variations in East Africa. The analysis of these cores will provide the necessary information about sedimentary processes in the Chew Bahir as required for detailed planning of deeper drilling in the Southern Ethiopian Rift within the framework of the ICDP "Hominid Sites and Paleolakes Drilling Project" project. The first objective is to study the type and character of sediment in the basin, in particular with respect to the organic matter including pollen and biomarkers. The second objective is to determine the sedimentation rates and its variation in the Chew Bahir based on a high-resolution AMS 14C chronology on parallel carbonate and charcoal samples to estimate possible reservoir effects. The third objective is to test controversially-discussed hypotheses about the timing, magnitude and synchronicity of the African Humid Period across the continent including the possible abruptness and internal variability of this event and the influence of this important dry-wet-dry shift in the tropics on the biosphere. The proposed project is linked to the ICDP "Hominid Sites and Paleolakes Drilling Project" initiative led by A. Cohen (U Arizona) proposing a drilling project to considering scientific opportunities and technical challenges of obtaining long (350 to 400 m) sediment cores from several of the most important fossil hominin and early Paleolithic artifact sites in the world, located in Kenya and Ethiopia, including Chew Bahir. This project is also linked to the DFG CRC-806 "Our way to Europe –Culture-Environment Interaction and Human Mobility in the Late Quaternary" providing funds for the first coring campaign of this project (Schäbitz, U Köln). The project is linked to all other projects on African climate change.

[19] Diekmann, Herzschuh – Postglacial landscape development and geoecological response to climate variability on the Tibetan Plateau. Environmental variability on the Tibetan Plateau mainly depends on changes in monsoon activity and its intersection with the westerly wind system. Other factors comprise glacial dynamics, neotectonic influence, and anthropogenic impact. The goal of our study is to exemplify the geoecological response of lake systems and their catchments to climate change during the last 20.000 years from the last glacial stage to the present interglacial (Holocene), addressing the following questions: (1) How do lacustrine environments respond to changes in landscape development, catchment hydrology, and variable detrital influxes by glacial, fluvial, aeolian and permafrost dynamics? (2) How do terrestrial vegetation and aquatic biotic communities respond to these abiotic environmental changes? (3) Are there environmental responses to non-climatic impulses (tectonics, human impact)? (4) Is regional climatic change on the Tibetan Plateau linked with supra-regional and global climate signals? (5) What is the nature of the recent warming phase against the backdrop of natural and anthropogenic impacts? Our study builds on the evaluation of environmental proxy records in lake-sediment cores, retrieved from selected lake sites on the northern Tibetan Plateau. The study is associated with the Potsdam Graduate School and will be financially supported by AWI Potsdam and other third-party sources. The project is linked to all other projects on Asian climate change.

[20] Strecker and colleagues – Assessing uplift, exhumation and erosion processes in the Kenya Rift through (U/Th)-He thermochronology and cosmogenic nuclide dating. Low temperature thermochronometry, particularly apatite (U-Th)/He dating, is a powerful tool to investigate exhumational cooling along major structures associated with extension. We strive to decipher the cooling history of basement rocks exposed the footwall of the northern Kenya Rift along the Elgeyo Escarpment, in order to identify episodes of rapid cooling and exhumation. The expected data will provide, for the first time, a good constraint on the timing of onset of rifting in this sector of the Kenya Rift, and provide new insights into the mechanisms and spatiotemporal patterns of regional doming, rifting and long-term climate change in the region. These processes have produced pronounced local relief, changes in the drainage network and depositional systems that have preserved tectonically and climatically forced sediment accumulations. Intervals of increased surface process rates during past humid phases that were associated with lake highstands in various rift sub-basins are analyzed with respect to paleo-erosion rates, which are compared to present-day, basin-wide erosion rates determined by cosmogenic nuclide dating. The chronology of key horizons containing material for the determination of paleo-erosion rates is accomplished via 40Ar/39Ar dating of intercalated ash horizons in lacustrine deposits. The project is linked to all other projects tectonics, climate and erosion in Africa, such as projects [10] and [17].

[21] Mischke and colleagues – The Quaternary environmental and climatic conditions in the Near East. The Quaternary environmental and climatic conditions in the Near East are of academic interest, and also significant for its present-day socioeconomic development. The Jordan Valley served as a migration corridor during the spread of hominins out of Africa in the early and middle Pleistocene. A large amount of archaeological information from famous excavation sites is in clear contrast to the rare information available thus far with respect to the overall environmental setting and the climate conditions during the migration waves. The proposed project has the aim to decipher the natural background of the hominin migration waves out of Africa. In addition, late Pleistocene and Holocene records will be investigated to determine the overall range of the environmental and climatic fluctuations in the Near East. Environmental and climatic conditions especially during the warmer periods of the Quaternary may be regarded as potential analogies for future climate change in a region which already faces enormous problems in water supply and sustainable use of water resources. Existing and newly developed tools for quantitative palaeoenvironmental and palaeoclimate reconstructions will be applied based on modern calibration data sets and multivariate statistical analysis. The project is linked to all other projects on Asian and African climate change, in particular projects [7], [8], [10], [18] and [19].

[22] Korup (DFG Heisenberg Fellow) and colleagues – Monsoon and earthquake controls on sediment flux in an arid bedrock landscape, Zanskar, India (DFG Project ZANSKAR). Quantifying rates of erosion and sediment flux has a long tradition in tectonically active mountain belts such as the Himalaya. Comparably little is known about the role of intermittent sediment storage and its implications for landscape evolution. The proposed project addresses this shortcoming, and aims to investigate the late Quaternary intramontane sedimentary record of the NW Himalayan humid-arid transition in the Zanskar region, India. Specific objectives include elucidating the causes that led to the formation and incision of large valley fills (fluvial and lake terraces, landslide deposits, etc.) in catchments otherwise dissected by steep bedrock rivers. A strengthened early Holocene monsoon circulation and large prehistoric earthquakes are among the most likely mechanisms to explain the rapid aggradation of valley floors that significantly delay fluvial bedrock incision, reduce local valley relief, buffer hillslope sediment delivery to river channels, and generally contribute to slowing down landscape response to tectonic uplift. Study methods will combine digital topographic and remote sensing analyses, radiometric age dating, sedimentological and morphometric field techniques, and numerical process modelling in order to quantify to first order the effects of large valley fills on late Quaternary landscape dynamics in the NW Himalaya. The project is linked to other projects on tectonics, climate and erosion in the Himalaya, such as projects [1], [2] and [3].

[23] Sachse, Tiedemann, Trauth, Herzschuh – The ultimate biomarker: Is a combined lipid biomarker isotope - ancient DNA approach able to assess changes in hydrology and vegetation in the catchment of small lakes? Due to the limitations of source-specifity of lipid biomarkers in sediments, especially regarding higher plant lipids, and the lack of our current understanding of the importance of plant physiological effects on the isotopic composition of such biomarkers, an interpretation of down-core variations in leaf-wax lipid δD values as a sole signal of hydrological changes is somewhat flawed. Pollen records can provide information on changing vegetation, but are not available from every sediment record and some issues due to long-range transport exist (Tyldesley, 1973). Recently it has been suggested that genetic information derived from so-called ancient DNA encountered in up to 400.000 year old sediments (Willerslev et al., 2003) can provide species-specific information on plants and animals living at the time of sediment deposition. Therefore, we propose to test the ability of ancient DNA to record a) the modern vegetation composition of the lake cacthement and b) known changes in vegetation (through historical records or pollen profiles) in the lake catchment of small lakes from different environments (boreal, temperate, tropical). Sediments from tropical lake Naivasha, as well as from temperate lake Meerfelder Maar and a boreal lake from Central Siberia will be used to test if a combined lipid biomarker hydrogen isotope – ancient DNA approach is capable of recording short-term changes in hydrology and vegetation. Part of the work will be conducted on sediments of tropical Lake Naivasha, in the central segment of the Kenya Rift in Africa, which has been shown to preserve diatom and rotifera DNA throughout the last several hundreds of years (Epp et al., in press; in revision). Leaf-wax lipids will be analyzed on the same core and their δD values will be used to reconstruct changes in hydrology within the catchment. The ancient DNA derived information on the dominant land plants will be used to separate vegetation change vs. hydrology change effects on the δD composition of leaf-wax lipids. The analysis of different proxies from the same core will determine the degree of effectiveness of DNA as a biomarker for terrestrial higher plants. The experience of researchers at the Institute of Geosciences of Universität Potsdam with the Lake Naivasha area as well as the experience of one of the few ancient DNA laboratories in Germany at the Institute for Biology at Universität Potsdam represent an ideal opportunity to further develop ancient DNA analysis into the “ultimate” biomarker.