Late Pleistocene to Holocene climate and limnological changes at Lake Karakul (Pamir Mountains, Tajikistan)
Liv Heinecke1,2, Steffen Mischke3, Karsten Adler2, Anja Barth4, Boris K. Biskaborn1, Birgit Plessen5, Ingmar Nitze1, Gerhard Kuhn6, Ilhomjon Rajabov7, and Ulrike Herzschuh1,21Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Research Unit Potsdam, Telegrafenberg A43, 14473 Potsdam, Germany 2Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany 3Faculty of Earth Sciences, University of Iceland, Sturlugata 7, Askja, 101 Reykjavík, Iceland 4Institute of Geological Sciences, Free University of Berlin, Malteserstr. 74-100; 12249 Berlin, Germany 5Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Sektion 5.2, Telegrafenberg C327, 14473 Potsdam, Germany 6Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, 27568 Bremerhaven, Germany 7Pilot Program for Climate Resilience Secretariat, Shevchenko Street 47, Dushanbe, Tajikistan
Abstract. Lake Karakul, located in the eastern Pamir Mountains, Tajikistan, is today dominated by the Westerlies. It is a matter of debate whether the Indian Monsoon influenced the region in the past. We analysed an 11.25 m sediment core covering the last 29,000 years to assess and separate lake-internal and lake-external processes, and to infer changes in the predominant atmospheric circulation. Among the parameters indicating lake-external processes, high values in grain-size end-member (EM) 3 (wide grain-size distribution, marking fluvial input) and Sr/Rb and Zr/Rb ratios (coinciding with coarse grain sizes, implying increased physical weathering) are interpreted as a strong monsoonal impact. High values in EM1, EM2 (peaking at small grain sizes reflecting Westerlies-derived dust) and TiO2 (terrigenous input) are assumed to reflect a strong influence of Westerlies. High input of far-transported dust from the pre-Last Glacial Maximum (LGM) to the late glacial reflects the Westerlies influence, while peaks in fluvial input suggest monsoonal influence. The early to early-mid Holocene is characterised by coarse mean grain sizes, increased physical weathering and constantly high fluvial input indicating a strengthened Indian Monsoon that reached further north into the Karakul region. A steady increase in terrigenous dust, decrease in fluvial input and physical weathering from 6.7 cal kyr BP onwards signals that Westerlies became the predominant atmospheric circulation and brought an arid climate to the region. Proxies for productivity (TOC, C/N, TOCBr), redox potential (Fe/Mn) and changes in the endogenic carbonate precipitation (TIC) indicate lake-internal changes. Low productivity characterised the lake from the late Pleistocene until 6.7 cal kyr BP and rapidly increased afterwards. The lake level remained low until the LGM, but water depth increased during the late glacial, reaching a high-stand during the early Holocene. Subsequently, the water level decreased until its present state. Today the lake system is mainly climatically controlled but the depositional regime is also driven by lake-internal limnogeological processes.
Heinecke, L., Mischke, S., Adler, K., Barth, A., Biskaborn, B. K., Plessen, B., Nitze, I., Kuhn, G., Rajabov, I., and Herzschuh, U.: Late Pleistocene to Holocene climate and limnological changes at Lake Karakul (Pamir Mountains, Tajikistan), Clim. Past Discuss., doi:10.5194/cp-2016-34, in review, 2016.