Abrupt climatic shift at ~4000 cal. yr B.P. and late Holocene climatic instability in arid Central Asia: Evidence from Lop Nur saline lake in Xinjiang, China.

Although the trends and driving mechanisms of Holocene climate change in arid Central Asia (ACA) on various timescales have attracted much research interest over the past few decades, a major question remains regarding whether the changes were gradual or abrupt. We reconstructed the pattern of Holocene climate change at Lop Nur saline lake in northwestern China, ACA, using multiple climatic proxies (grain size, TOC, sediment color, and magnetic properties). The results demonstrate that the Holocene climatic pattern in the Lop Nur region during the past 8400 years can be divided into two distinct stages, with the boundary dated to ~4000 cal. yr B.P. During the first stage (8400-4000 cal. yr B.P.), the climate was relatively dry and stable; and during the second stage the climate was more humid with high-amplitude variations. This finding is corroborated by other paleoclimatic records from the surrounding area and it is also consistent with the latest international strata chronology for the Holocene. The abrupt climatic shift at ~4000 cal. yr B.P. and late Holocene climatic instability in ACA are highlighted in this study. The decreasing temperatures in the study region during the middle to late Holocene were modulated by Northern Hemisphere summer insolation, which led to decreasing evaporation and thus to the wetting trend of the middle through late Holocene. The abrupt change at ~4000 cal. yr B.P. was caused mainly by a more negative trend of the North Atlantic Oscillation (NAO) and by an enhanced El Niño - Southern Oscillation (ENSO).