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

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 (similar to 5-year resolution), and major and trace elements (similar to 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.

Automated summary

Paleoclimatic records from lake sediment cores in arid central Asia suggest a humid climate in the Little Ice Age compared to the contemporary warm period. A high-resolution study of a sediment core from Yileimu Lake indicates a warming and wetting trend in the southern Altay regional climate over the last five centuries, potentially driven by increasing snow/ice meltwater, rising atmospheric temperatures, and a decreasing winter North Atlantic Oscillation index.