Moisture dynamics in central Asia for the last 15 kyr: new evidence from Yili Valley, Xinjiang, NW China

Abstract

Based on high resolution palynological investigations and AMS 14C dating, the continuous lacustrine sediments contained in Yili Valley, Xinjiang provide an opportunity to reconstruct the effective moisture changes for the last 15 kyr in central Asia. The relatively warm and humid climate of the Bølling-Allerød (15–12.9 cal kyr BP) is a generalization, but it seems to show some fluctuations. The time of the Younger Dryas (YD) interrupted the increasing trend of effective moisture in the study region, the climate was cold and relatively dry in the early YD period (12.9–12.0 cal kyr BP), whereas the desert vegetation community appeared around 11.8 cal kyr BP, almost the driest time since the 15 cal kyr BP. A sharp increase in effective moisture marked the beginning of the Holocene in the Yili Valley. The early Holocene (10.6–7.6 cal kyr BP) was the wettest time with a developed temperate steppe. A dry climate with desert vegetation arose in the early mid-Holocene (7.6–6.5 cal kyr BP), spanning 1100 years. A second humid phase emerged between 6.5 and 5.2 cal kyr BP, whose vegetation community was represented by temperate steppe. Moisture was reduced again and the climate became drier between 5.2 and 3.3 cal kyr BP when vegetation was dominated by desert steppe in the Yili Valley. Regional comparisons indicate that the moisture changes in Yili Valley were mainly influenced by the North Atlantic Ocean SSTs through the westerlies. The mean position of the Siberian High Pressure cell probably made a great contribution to the drought between 7.6 and 6.5 cal kyr BP. The climate changes were generally consistent between the westerly-dominant central Asia and Asian monsoon regions since the last deglaciation, possibly forced by summer insolation conditions in the Northern Hemisphere.