Humid Little Ice Age in arid central Asia documented by Bosten Lake, Xinjiang, China

Abstract

Short sediment cores retrieved from Bosten Lake, the largest inland freshwater lake in China, were used to explore humidity and precipitation variations in arid central Asia during the past millennium. The chronology of the cores was established using 137 Cs, 210 Pb and AMS 14 C dating results. Multi-proxy high-resolution analysis, including pollen ratios of Artemisia and Chenopodiaceae (A/C), carbonate content and grain size, indicates that the climate during the past millennium can be divided into three stages: a dry climate between 1000-1500 AD, a humid climate during the Little Ice Age (LIA) (c. 1500-1900 AD), and a warm dry period after 1900 AD. On centennial timescales, the climate change in northwestern China during the past 1000 years is characterized by oscillations between warm-dry and cold-humid climate conditions. All the proxies changed significantly and indicate increased precipitation during the LIA, including increased pollen A/C ratios and pollen concentrations, decreased carbonate content and increased grain size. The humid period during the LIA recorded by the Bosten Lake sediments is representative of arid central Asia and is supported by numerous records from other sites. During the LIA, the water runoff into the Keriya River and Tarim River in the Tarim Basin increased, while the ice accumulation in the Guliya ice core increased. Additionally, the lake levels of the Aral and Caspian Sea also rose, while tree-ring analysis indicates that precipitation increased. We hypothesize that both the lower temperature within China and the negative anomalies of North Atlantic Oscillation (NAO) during this period may have contributed to the humid climate within this area during LIA.

Pollen source areas of lakes with inflowing rivers: modern pollen influx data from Lake Baiyangdian, China

“…Lacustrine pollen is an important proxy for reconstructing paleovegetation and paleoclimate, because pollen grains are usually well preserved in lake sediments (Sun and Wu, 1987;Gasse et al, 1991;Chen et al, 2006). Interpretation of the pollen signal and reconstruction of palaeovegetation is underpinned by assumptions about the spatial area reflected by the pollen signal and the taphonomy of different pollen types.…”

Humid medieval warm period recorded by magnetic characteristics of sediments from Gonghai Lake, Shanxi, North China

“…In China, regional differences in hydroclimatic characteristics during the MWP also clearly existed. In arid northwestern China, the proxy records derived from lacustrine sediments [25,26], aeolian deposits [27] and tree rings [28] all show a dry MWP and a wet LIA in general [29]. The Asian summer monsoon is an important component of global climate system and its variability is always of great interest in paleoclimatological studies at a wide range of time scales [30,31].…”

Hydrological extremes in the Aksu-Tarim River Basin: Mid-latitude dynamics

“…Also other large-scale circulation indices considered suggest a close relation between extremes of the hydrological cycle in the Tarim River Basin and large-scale mid-latitude circulation in particular in the Atlantic and European sector (Wang et al 2014). Time series from paleo and more recent climate archives show oscillations between dry and wet periods since at least 4000 years (Zhao et al 2012;Chen et al 2006a) and a connection to climate extremes in the NorthAtlantic sector (Bond et al 1997). On an interannual time scale teleconnection patterns are found linking extremes of the hydrological cycle on different continents (Lau and Weng 2002;Wallace and Gutzler 1981;Ding and Wang 2005;Conversi et al 2010;Zhu et al 2011).…”