Distinct responses of Asian summer monsoon to the Orbital forcing during the last glacial Heinrich events
(2024) 2024-EGU General Assembly 2024 — Location: Vienna, Austria
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- Climatic fingerprint of Heinrich (H) events was characterized by widespread megadroughts over the Asian monsoon region accompanied by systemic weakening of Asian summer monsoon. However, recent hydroclimate proxies suggest that South China experienced increased precipitation contrasting with the prevalent megadroughts conditions during the Heinrich events. Considered that insolation is the most important known external forcing of the climate system, it is worthwhile to investigate whether variations in insolation alone can account for the precipitation spatiotemporal discrepancies and its underlying mechanism. Here, six snapshot simulations, varying exclusively with insolation during the last glacial Heinrich events, are performed with the HadCM3 model and show that changes in insolation alone can induce spatiotemporal discrepancies in precipitation over the Asian summer monsoon region. During the H1, 3, 4, 5, 6 events, the amplification of the land-sea pressure contrast in response to a positive solar insolation gradient during boreal summer intensifies moisture transport from the ocean to the Asian monsoon region. The ensuing moisture divergence, combined with anomalous downdrafts, results in decreased precipitation in the South Asian Summer Monsoon (SASM) region, but converse scenario for the East Asian Summer Monsoon (EASM) region. During the H2 event, the increased precipitation across the Yangtze River Valley sharply contrasts with the widespread drought over the ASM region, this increased precipitation is attributed to enhancement of southerly warm and moist vapor transport, coupled with northerly cold and dry vapor transport, along the western edge of the subtropical Western North Pacific anticyclone and the Aleutian cyclone, converging over the Yangtze River Valley. Furthermore, we examine relationship between the intensity of the EASM and SASM under orbital forcing. Our results indicate that in phase of SASM and EASM is driven by the combined influence of the land-sea thermal contrast and the migration of the Intertropical Convergence Zone, supporting Kutzbach's hypothesis.
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Liang, M., Yin, Q., Yong Sun, Chao Zhang, Wu, Z., Liu, W., & et al. (2024). Distinct responses of Asian summer monsoon to the Orbital forcing during the last glacial Heinrich events. 2024-EGU General Assembly 2024, Vienna, Austria.