Precipitation reconstruction since the last deglacial based on the stable carbon isotopic composition of a loess section in western Central Asia

Abstract

The topography of the Tianshan Mountains and the Pamir Plateau strongly shapes the seasonality of precipitation in Central Asia (CA): cold-season (October-April) precipitation dominates western CA and warm-season (May-September) precipitation dominates eastern CA. The precipitation/moisture patterns between western and eastern CA are completely opposite at seasonal, decadal and centennial scale. However, the pattern contrasts for millennial or longer time scales remain unknown. In this study, we investigated the precipitation variations in western CA, as recorded in a 6.5-m loess section in southern Kazakhstan, which has accumulated since ~14.4 ka. According to the robust relationship between the surface soil organic matter δ13C and the climatic parameters, the δ13C signature is here considered as a precipitation proxy. The record reveals an overall decreasing precipitation before ~6.0 ka followed by an increasing trend afterward, being consistent with the previously reported precipitation records in western CA. The late-deglaciation precipitation in western CA is in phase with that in eastern CA at millennial scales, which are both driven by the North Atlantic Oscillation (NAO) and the Siberian High.