Anomalous warm winters on the southeastern Tibetan Plateau during the 8.2 ka cold event: Implications for recent warming amplification

Abstract

Holocene climate changes exhibited pronounced millennial-scale oscillations in response to the slowdown of the Atlantic meridional overturning circulation (AMOC). Millennial-scale temperature variations on the southeastern Tibetan Plateau remain an ongoing topic of scientific debate. This study explores winter temperature variations on the southeastern Tibetan Plateau during the 8.2 ka cold event using climate simulations driven by North Atlantic freshwater forcing. Our hosing simulations reveal anomalous winter warming on the southeastern Tibetan Plateau in response to the AMOC weakening during the 8.2 ka cold event. This anomalous warming was due to mid-tropospheric southwesterly anomalies extending from the tropical Indian Ocean to the southeastern Tibetan Plateau, leading to significant warm advection into the southeastern Tibetan Plateau. These mid-tropospheric southwesterly anomalies were induced by the intensification of the southern bypassing flows, which originated from an anomalous anticyclone over the tropical Indian Ocean. The anomalous anticyclone resulted from a Rossby-like wave train originating in the North Atlantic, which was triggered by the North Atlantic cooling due to the AMOC weakening. Hence, the AMOC weakening induced anomalous winter warming on the southeastern Tibetan Plateau during the 8.2 ka cold event. Analogous to the 8.2 ka cold event, the southeastern Tibetan Plateau experiences increased winter temperatures due to the weakening of the AMOC. The weakened AMOC has probably amplified the winter warming on the southeastern Tibetan Plateau in recent decades.