TY - JOUR A1 - Ramisch, Arne A1 - Tjallingii, Rik A1 - Hartmann, Kai A1 - Diekmann, Bernhard A1 - Brauer, Achim T1 - Echo of the Younger Dryas in Holocene Lake Sediments on the Tibetan Plateau JF - Geophysical research letters N2 - Reading the sediment record in terms of past climates is challenging since linking climate change to the associated responses of sedimentary systems is not always straightforward. Here we analyze the erosional response of landscapes on the Tibetan Plateau to interglacial climate forcing. Using the theory of dynamical systems on Holocene time series of geochemical proxies, we derive a sedimentary response model that accurately simulates observed proxy variation in three lake records. The model suggests that millennial variations in sediment composition reflect a self-organization of landscapes in response to abrupt climate change between 11.6 and 11.9 ka BP. The self-organization is characterized by oscillations in sediment supply emerging from a feedback between physical and chemical erosion processes, with estimated response times between 3,000 to 18,000 years depending on catchment topography. The implications of our findings emphasize the need for landscape response models to decipher the paleoclimatic code in continental sediment records. Plain Language Summary Lake sediments are an important source of information on past climates. Reading the information is not always straightforward. Complex interactions in landscapes can affect the transmission of climatic signals to the sediment record. However, the exact nature of such complex interactions remains unknown. This study compares sediment deposits of three lakes on the Tibetan Plateau. The deposits are continuous records of landscape responses to climate change during the last 12,000 years. We identified a mathematical model that accurately simulates changes in sediment composition at all sites. The model simulations suggest that an abrupt warming at the end of the last glacial period destabilized the landscapes. This caused fluctuations in the transport of sediments, which persisted for several thousand years. Our findings present evidence for a long-lasting impact of abrupt climate change on fundamental Earth surface processes. Y1 - 2018 U6 - https://doi.org/10.1029/2018GL080225 SN - 0094-8276 SN - 1944-8007 VL - 45 IS - 20 SP - 154 EP - 163 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Ramisch, Arne A1 - Tjallingii, Rik A1 - Hartmann, Kai A1 - Diekmann, Bernhard A1 - Brauer, Achim T1 - Echo of the Younger Dryas in Holocene Lake Sediments on the Tibetan Plateau JF - Geophysical research letters N2 - Reading the sediment record in terms of past climates is challenging since linking climate change to the associated responses of sedimentary systems is not always straightforward. Here we analyze the erosional response of landscapes on the Tibetan Plateau to interglacial climate forcing. Using the theory of dynamical systems on Holocene time series of geochemical proxies, we derive a sedimentary response model that accurately simulates observed proxy variation in three lake records. The model suggests that millennial variations in sediment composition reflect a self-organization of landscapes in response to abrupt climate change between 11.6 and 11.9 ka BP. The self-organization is characterized by oscillations in sediment supply emerging from a feedback between physical and chemical erosion processes, with estimated response times between 3,000 to 18,000 years depending on catchment topography. The implications of our findings emphasize the need for landscape response models to decipher the paleoclimatic code in continental sediment records. Plain Language Summary Lake sediments are an important source of information on past climates. Reading the information is not always straightforward. Complex interactions in landscapes can affect the transmission of climatic signals to the sediment record. However, the exact nature of such complex interactions remains unknown. This study compares sediment deposits of three lakes on the Tibetan Plateau. The deposits are continuous records of landscape responses to climate change during the last 12,000 years. We identified a mathematical model that accurately simulates changes in sediment composition at all sites. The model simulations suggest that an abrupt warming at the end of the last glacial period destabilized the landscapes. This caused fluctuations in the transport of sediments, which persisted for several thousand years. Our findings present evidence for a long-lasting impact of abrupt climate change on fundamental Earth surface processes. Y1 - 2018 U6 - https://doi.org/10.1029/2018GL080225 SN - 0094-8276 SN - 1944-8007 VL - 45 IS - 20 SP - 11154 EP - 11163 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Ramisch, Arne A1 - Lockot, Gregori A1 - Haberzettl, Torsten A1 - Hartmann, Kai A1 - Kuhn, Gerhard A1 - Lehmkuhl, Frank A1 - Schimpf, Stefan A1 - Schulte, Philipp A1 - Stauch, Georg A1 - Wang, Rong A1 - Wunnemann, Bernd A1 - Yan, Dada A1 - Zhang, Yongzhan A1 - Diekmann, Bernhard T1 - A persistent northern boundary of Indian Summer Monsoon precipitation over Central Asia during the Holocene JF - Scientific reports N2 - Extra-tropical circulation systems impede poleward moisture advection by the Indian Summer Monsoon. In this context, the Himalayan range is believed to insulate the south Asian circulation from extra-tropical influences and to delineate the northern extent of the Indian Summer Monsoon in central Asia. Paleoclimatic evidence, however, suggests increased moisture availability in the Early Holocene north of the Himalayan range which is attributed to an intensification of the Indian Summer Monsoon. Nevertheless, mechanisms leading to a surpassing of the Himalayan range and the northern maximum extent of summer monsoonal influence remain unknown. Here we show that the Kunlun barrier on the northern Tibetan Plateau [similar to 36 degrees N] delimits Indian Summer Monsoon precipitation during the Holocene. The presence of the barrier relocates the insulation effect 1,000 km further north, allowing a continental low intensity branch of the Indian Summer Monsoon which is persistent throughout the Holocene. Precipitation intensities at its northern extent seem to be driven by differentiated solar heating of the Northern Hemisphere indicating dependency on energy-gradients rather than absolute radiation intensities. The identified spatial constraints of monsoonal precipitation will facilitate the prediction of future monsoonal precipitation patterns in Central Asia under varying climatic conditions. Y1 - 2016 U6 - https://doi.org/10.1038/srep25791 SN - 2045-2322 VL - 6 SP - 596 EP - 633 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Opitz, Stephan A1 - Wünnemann, Bernd A1 - Aichner, Bernhard A1 - Dietze, Elisabeth A1 - Hartmann, Kai A1 - Herzschuh, Ulrike A1 - IJmker, Janneke A1 - Lehmkuhl, Frank A1 - Li, Shijie A1 - Mischke, Steffen A1 - Plotzki, Anna A1 - Stauch, Georg A1 - Diekmann, Bernhard T1 - Late Glacial and Holocene development of Lake Donggi Cona, north-eastern Tibetan Plateau, inferred from sedimentological analysis JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - Sediments of Lake Donggi Cona on the northeastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment, related to climatic and non-climatic changes during the last 19 kyr. The lake today fills a 30x8 km big and 95 m deep tectonic basin, associated with the Kunlun Fault. The study was conducted on a sediment-core transect through the lake basin, in order to gain a complete picture of spatio-temporal environmental change. The recovered sediments are partly finely laminated and are composed of calcareous muds with variable amounts of carbonate micrite, organic matter, detrital silt and clay. On the basis of sedimentological, geochemical, and mineralogical data up to five lithological units (LU) can be distinguished that document distinct stages in the development of the lake system. The onset of the lowermost LU with lacustrine muds above basal sands indicates that lake level was at least 39 m below the present level and started to rise after 19 ka, possibly in response to regional deglaciation. At this time, the lacustrine environment was characterized by detrital sediment influx and the deposition of siliciclastic sediment. In two sediment cores, upward grain-size coarsening documents a lake-level fall after 13 cal ka BP, possibly associated with the late-glacial Younger Dryas stadial. From 11.5 to 4.3 cal ka BP, grain-size fining in sediment cores from the profundal coring sites and the onset of lacustrine deposition at a litoral core site (2 m water depth) in a recent marginal bay of Donggi Cona document lake-level rise during the early to mid-Holocene to at least modern level. In addition, high biological productivity and pronounced precipitation of carbonate micrites are consistent with warm and moist climate conditions related to an enhanced influence of summer monsoon. At 4.3 cal ka BP the lake system shifted from an aragonite- to a calcite-dominated system, indicating a change towards a fully open hydrological lake system. The younger clay-rich sediments are moreover non-laminated and lack any diagenetic sulphides, pointing to fully ventilated conditions, and the prevailing absence of lake stratification. This turning point in lake history could imply either a threshold response to insolation-forced climate cooling or a response to a non-climatic trigger, such as an erosional event or a tectonic pulse that induced a strong earthquake, which is difficult to decide from our data base. KW - China KW - Monsoon KW - Paleolimnology KW - Multi-site study KW - Aragonite KW - XRF KW - XRD KW - Sedimentology Y1 - 2012 U6 - https://doi.org/10.1016/j.palaeo.2012.04.013 SN - 0031-0182 VL - 337 IS - 23 SP - 159 EP - 176 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hülscher, Julian A1 - Sobel, Edward A1 - Kallnik, Niklas A1 - Hoffmann, J. Elis A1 - Millar, Ian L. A1 - Hartmann, Kai A1 - Bernhardt, Anne T1 - Apatites record sedimentary provenance change 4-5 myrs before clay in the Oligocene/Miocene Alpine molasse JF - Frontiers in Earth Science N2 - Extracting information about past tectonic or climatic environmental changes from sedimentary records is a key objective of provenance research. Interpreting the imprint of such changes remains challenging as signals might be altered in the sediment-routing system. We investigate the sedimentary provenance of the Oligocene/Miocene Upper Austrian Northern Alpine Foreland Basin and its response to the tectonically driven exhumation of the Tauern Window metamorphic dome (28 +/- 1 Ma) in the Eastern European Alps by using the unprecedented combination of Nd isotopic composition of bulk-rock clay-sized samples and partly previously published multi-proxy (Nd isotopic composition, trace-element geochemistry, U-Pb dating) sand-sized apatite single-grain analysis. The basin offers an excellent opportunity to investigate environmental signal propagation into the sedimentary record because comprehensive stratigraphic and seismic datasets can be combined with present research results. The bulk-rock clay-sized fraction epsilon Nd values of well-cutting samples from one well on the northern basin slope remained stable at similar to-9.7 from 27 to 19 Ma but increased after 19 Ma to similar to-9.1. In contrast, apatite single-grain distributions, which were extracted from 22 drill-core samples, changed significantly around 23.3 Ma from apatites dominantly from low-grade (