Southward shift of the Westerlies during Heinrich Event 2: Evidence from loess deposits in Central Asia

Abstract

Knowledge of past changes in the Westerlies is important for understanding the climatic and environmental evolution of Central Asia. Here, we use high-resolution grain size records from several loess deposits in Central Asia to study the spatial pattern of the Westerlies during an interval of high global ice volume during the Last Glacial Maximum. During Heinrich event 2 (H2), the Westerlies strengthened in southern Central Asia, as indicated by the high accumulation rate of dust transported by the Westerlies, while it decreased in northern Central Asia. Our grain size record, combined with climate modeling results, suggest that the main axis of the Westerlies strengthened and moved southward to southern Central Asia during Heinrich events, especially H2. Comparison with other climate records from East Asia indicates that a southward shift of the Westerlies may influence the extension of the downstream East Asian Summer monsoon rain belt into north and northwest China. Thus, the position and strength of the mid-latitude Westerlies need to be considered in future studies of the Asian monsoon.