Centennial-scale East Asian winter monsoon variability within the Younger Dryas

Abstract

The Younger Dryas (YD) is recognized as a millennial-scale cold climate event that occurred during the last deglaciation in the Northern Hemisphere. Modeling and geological evidences reveal that the YD period was punctuated by multiple rapid changes at interdecadal to centennial timescales. However, characteristics and mechanism of abrupt climate variability within the YD in its most pronounced winter interval remain poorly constrained. Here, we present two high-resolution loess grain-size time series from the western Chinese Loess Plateau (CLP) to address centennial-scale East Asian winter monsoon (EAWM) variability during this phenomenal cooling event. The mean grain size results reveal two cold intervals of the Heinrich event 1 and YD during the last deglaciation, corresponding well to climate changes from regional and global context. More importantly, the mean grain size results demonstrate a persistent centennial-scale EAWM variability within the YD. We propose that this was caused by the North Atlantic sea ice variation via fast atmospheric processes between the subpolar and mid-latitude regions. We also observed a marked decrease in magnitudes of centennial-scale EAWM variability around the mid-YD. Such a mid-YD shift is closely related to a northward shift of the atmospheric polar front and sea ice retreat induced by the resumption of the Atlantic meridional overturning circulation (AMOC). Our results suggest that the AMOC-induced sea ice change in the North Atlantic plays a more dominant role than the AMOC itself in transmitting abrupt climate signals over the Northern Hemisphere.