A 450-year warming and wetting climate in southern Altay inferred from a Yileimu Lake sediment core

Abstract

Numerous paleoclimatic records from lake sediment cores in arid central Asia (ACA) suggest a more humid climate in the Little Ice Age (LIA) cold period than that of the contemporary warm period (the last century). Our high-resolution study of a sediment core from Yileimu Lake presents end members (EMs) of grain-size distributions (~5-year resolution), and major and trace elements (~10-year resolution), including the Chemical Index of Alteration (CIA) and Rb/Sr ratio. In contrast to records from these other lakes in ACA, our study indicates a warming and wetting trend in the southern Altay regional climate over the last five centuries. We suggest that continuously increasing snow/ice meltwater from the surrounding high mountains related to an increasing trend in atmospheric temperature, and increasing winter snowfall triggered by a decreasing trend in winter North Atlantic Oscillation (NAO) index, have dominated the regional climate in the southern Altay Mountains during 1620–1835 AD. We also suggest that temperature dependent evaporative losses greatly exceeding the water input to the lake, and reduced summer precipitation, caused the drought events during 1586–1620 and 1835–1870 AD. Heavy summer precipitation associated with significant increases in the local moisture supply induced by intense evaporation of snow/ice meltwater in the alpine and gorge terrain of the Altay Mountains played a critical role in the summer floods around the 1900s AD.