Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years

Abstract

In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio)geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100–4350, 3450–2850, and 1900–1500 cal. yr BP. The distinct ~1500- year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia

Biomolecular Evidence of Early Human Occupation of a High-Altitude Site in Western Central Asia During the Holocene

“…the lake from the north-east. The present-day regional climate is temperate continental (Wang et al, 2017) and dominated by the interaction between the Siberian anticyclonic circulation and the mid-latitude Westerlies (Aizen et al, 1997;Lauterbach et al, 2014). Owing to the high mountain ranges of the Tian Shan that prevent the transport of moisture, rainfall is reduced, especially in January and February (Aizen et al, 1995(Aizen et al, , 2001.…”

“…Paleoenvironmental studies from Kyrgyzstan indicate rather dry conditions during Phase II. Lauterbach et al (2014) reported a pronounced dry interval for Lake Son Kul between 4,950 and 3,900 cal a BP. In accordance, a stalagmite record from Uluu-2 Cave, ∼250 km west of Lake Chatyr Kol, also suggests dry conditions between 4,700 and 3,900 cal a BP (Wolff et al, 2017).…”

High-amplitude lake-level changes in tectonically active Lake Issyk-Kul (Kyrgyzstan) revealed by high-resolution seismic reflection data

“…The midlatitude Westerlies bring moisture from the Aral-Caspian Basin, the Mediterranean, the Black Sea and the North Atlantic (Aizen et al, 2006;Lauterbach et al, 2014), while the Asian summer monsoon has only been of minor importance, at least since the midHolocene (Cheng et al, 2012). The Siberian High reaches south to the Tien Shan area and blocks the midlatitude Westerlies during winter, which results in low winter precipitation due to the dry air masses of the Siberian High (Aizen et al, 1995(Aizen et al, , 2001Ricketts et al, 2001).…”

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

“…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.…”