Late Pleistocene to Holocene climate and limnological changes at Lake Karakul (Pamir Mountains, Tajikistan)

Abstract

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.

Underlying causes of Eurasian midcontinental aridity in simulations of mid‐Holocene climate

“…Lake status is an index of the water balance (precipitation minus evaporation) over the lake and its catchment. Lake histories produced since the publication of the GLSDB have also been compiled and are included in our analyses—see the supporting information for details [ Bird et al ., ; Boomer et al ., ; Chen et al ., ; Chawchai et al ., ; Chen et al ., ; Ferronskii et al ., ; Fowell et al ., ; Gasse et al ., ; Grunert et al ., ; Kong et al ., ; Heinecke et al ., ; Herzschuh et al ., ; Hodell et al ., ; Huang et al ., , ; Jiang et al ., ; Jiang and Liu , ; Li and Morrill , ; Li et al ., , , ; Long et al ., ; Madsen et al ., ; Mathis et al ., ; Mingram et al ., ; Morinaga et al ., ; Morrill et al ., ; Pan et al ., ; Peck et al ., ; Penny et al ., ; Prokopenko et al ., ; Rades et al ., ; Ricketts et al ., ; Schwanghart et al ., ; Shen et al ., ; Sheng et al ., ; Wang et al ., ; Wang and Ji , ; Wünnemann et al ., , ; Xiao et al ., ; Yang et al ., ; Zhang et al ., , ; Zhao et al ., , , ; Zhou et al ., ]. BIOME 6000 provides pollen‐based reconstructions of vegetation for the MH [ Prentice et al ., ; Bigelow et al ., ], and the reconstructions for Eurasia have been updated by Binney et al .…”

“…Lake status is an index of the water balance (precipitation minus evaporation) over the lake and its catchment. Lake histories produced since the publication of the GLSDB have also been compiled and are included in our analyses-see the supporting information for details [Bird et al, 2014;Boomer et al, 2000;Chen et al, 2008;Chawchai et al, 2013;Chen et al, 2003;Ferronskii et al, 2003;Fowell et al, 2003;Gasse et al, 1996;Grunert et al, 2000;Kong et al, 2007;Heinecke et al, 2016;Herzschuh et al, 2004;Hodell et al, 1999;Huang et al, 2009Huang et al, , 2014Li and Morrill, 2010;Li et al, 2011Li et al, , 2014aLi et al, , 2014bLong et al, 2012;Madsen et al, 2008;Mathis et al, 2012;Mingram et al, 2004;Morinaga et al, 1993;Morrill et al, 2006;Pan et al, 2012;Peck et al, 2002;Penny et al, 1996;Prokopenko et al, 2007;Rades et al, 2015;Ricketts et al, 2001;Schwanghart et al, 2008;Shen et al, 2005;Sheng et al, 2017;Wang et al, 2017;Wang and Ji, 1995;Wünnemann et al, 2003Wünnemann et al, , 2006Xiao et al, 2008;Yang et ...…”

Climate Change and the Rise and Fall of the Oxus Civilization in Southern Central Asia

“…At the lake Issyk Kul in Kyrghystan, Ricketts et al (2001) identified a change in the climatic condition of the basin around 6900 BP (transition from a fresh-water open-basin, well-mixed system to a closed-basin, more saline and relatively poorly mixed system) related to increasing aridity and atmospheric changes, diagnosed as the strengthening of the Siberian High, or the weakening of the Southwest Asian Low (Indian monsoon). The development of the Lake Karakul in Tajikistan marked by a reduction of the lake levels from 6600 BP suggests a similar aridification of the climate (Heinecke et al 2016). Later, from 4200 to 3500 BP, a high water level resulting from an intake from the melting of glaciers, snow fields and frozen grounds indicates warm climatic conditions, whereas subsequently (3500-1600 BP), a rapid cooling and a lower water level has been reconstructed (Mischke et al 2010).…”

“…As one of the driest areas in the world, southern Central Asia is undergoing the influence of different climatic systems at different space and time scales, but presently dominated by prevailing winds from the West, so-called 'westerlies' (Cheng et al 2012(Cheng et al , 2016Heinecke et al 2016;Lauterbach et al 2014;Wang et al 2010). It belongs to the desert climatic zones, with a semi-arid to arid climate, characterized by low rainfall from the end of fall to mid spring and by a maximum exposure to the sun and high temperatures the rest of the year (Mannig et al 2013).…”

“…In central Asia, Palaeoclimate studies particularly investigated the relationships between the atmospheric circulation and high-mountain environments through alpine and subalpine lake records (Beer et al 2007;Heinecke et al 2016;Lauterbach et al 2014;Mischke et al 2010;Ricketts et al 2001). These studies infer the decrease of the influence of the Monsoon and the dominance of the Westerlies, bringing arid conditions during the second half of the Mid-Holocene to the present.…”