Late Holocene hydroclimatic variation in central Asia and its response to mid-latitude Westerlies and solar irradiance

Abrupt Freshening Since the Early Little Ice Age in Lake Sayram of Arid Central Asia Inferred From an Alkenone Isomer Proxy

“…Our salinity record displays relative freshening of lake water at two intervals of about CE 1150–1550 and 1850 to present since the early LIA, which is consistent with the effective moisture records of the published δ 18 O and δ 13 C values of bulk carbonate in Lake Sayram (Lan et al, 2020) (Figures 3d and 3e). The relatively wet periods appear to be recorded broadly in other moisture records in the core area of ACA, including Artemisia and Chenopodiaceae pollen ratio (A/C ratio) in Lake Aibi (W. Wang & Feng, 2013), A/C ratio and δ 13 C values of cellulose in Big Black peatland (Xu et al, 2019), magnetic properties (Chen et al, 2016) and δ 13 C values of bulk organic matter (Xie et al, 2018) in Lujiaowan loess, and accumulation of the Guliya ice core on the northwestern Tibetan Plateau (T. Yao et al, 1996) (Figures 3f–3i).…”

“…The intensity of the westerlies and the location of the westerly jet may play an important role in controlling the overall rainfall pattern in the core area of ACA on multicentennial and millennium time scales (Chen et al, 2019). The larger meridional thermal gradient between high and middle latitudes and the negative phase of North Atlantic Oscillation (NAO), as two potential driving factors, can directly or indirectly lead to a strengthening of westerly winds and southward movement of the westerly jet (e.g., Chen et al, 2019; Lan et al, 2020). This can bring more water vapor supply from the major water bodies (Mediterranean Sea, Black Sea, and Caspian Sea, even North Atlantic) (Jin et al, 2012; S. Wang et al, 2017) to the core area of ACA along the westerly pathways.…”

“…All collected samples were kept in a cooler with gel ice packs in the field and then frozen at −20°C in the laboratory until analysis. The age profile of another parallel sediment core (SLM13‐2‐1) has been well established by 137 Cs‐ 210 Pb dating and a 14 C model (Lan et al, 2019, 2020). Bulk carbonate contents in our sediment core were determined by titration with diluted perchloric acid (HClO 4 ; 0.1 mol L −1 ) for comparison with previously published values in another core (SLM13‐2‐1; Table S1 in the supporting information; Lan et al, 2019).…”

“…Numerous studies have reconstructed the hydroclimatic changes of the core area of ACA over different time scales from various geological archives, such as lake sediments (e.g., Chen et al, 2008; Lan et al, 2018, 2019, 2020; Rudaya et al, 2009; W. Wang & Feng, 2013), stalagmites (e.g., Cai et al, 2017; Cheng et al, 2012, 2016), loess deposits (e.g., Chen et al, 2016; Ran & Feng, 2014), and peats (Hong et al, 2014; Xu et al, 2019). Most of these studies focused on effective moisture changes during the Holocene or longer time scales; the moisture evolution of the past two millennia and its driving mechanisms in the region, however, are still poorly understood, largely due to influence of the nonmoisture factors on the proxies employed and/or relatively large age uncertainties on such short time scales.…”

Humid and cold periods in the last 5600 years in Arid Central Asia revealed by palynology of Picea schrenkiana from Issyk-Kul

“…With the Picea increase, starts a longer-term charcoal increase. The record of lake Sayram (N Xinjiang) (Lan et al, 2020) shows five phases of enhanced effective moisture, the first one being in the interval of 4000-3780 yr BP. According to the map of Wang et al (2016), the impact of the 4.2 ka event is so far unknown in Kirghizstan and surroundings and might be equally drier or wetter.…”