Hydroclimatic differences over the past 2300 years in arid Central Asia and their potential impacts on human activities revealed by End Member Modelling Analysis of lake sediments

The arid Central Asia (ACA) is highly sensitive to global changes, making it critical for climate and environmental change research. Previous studies have demonstrated that the ACA experienced different hydroclimatic conditions during the late Holocene; however, the specific details remain insufficiently explored. In this study, we investigate hydroclimatic variations over the past 2300 years using End Member Modelling Analysis (EMMA) of grain size, combined with multi-proxy indices from Lake Bosten. Our results reveal distinct intervals: two wet intervals during 320–44 BCE (before the Common Era) and 1350–1935 CE (Common Era); and one dry interval during 44 BCE–1350 CE. We propose that NAO (North Atlantic Oscillation) may have influenced these hydroclimatic changes in arid Central Asia. Our findings suggest that wet conditions would favor traditional agricultural activities, thereby promoting the unity and prosperity of ancient cities. In contrast, during the dry interval, nomadic tribes expanded southward, leading to frequent wars and political instability.