Migration of Afro-Asian Monsoon Fringe Since Last Glacial Maximum

Abstract

Geological records indicated the termination of the Holocene Thermal Maximum (dramatic drying) occurred progressively later at lower latitudes in both North Africa and East Asia, along with the coherent weakening of local summer monsoon. Here we show that this time-transgressive evolution was dominated by the southward migration of monsoon fringe (shrinking monsoon domain) under monsoon weakening, as illustrated in a transient climate-terrestrial ecosystem model simulation. The monsoon fringe retreating southward during the Holocene, as well as expanding northward during the last deglaciation, occurred synchronously in a belt extending from North Africa to East Asia, which induced a locally humid-arid transition and the subsequent dramatic environment impact. The migration of Afro-Asia monsoon fringe since the Last Glacial Maximum was modulated by the orbital forcing through its impact on land-ocean thermal contrast, aiding by the variation of CO 2 concentration.

External Forcings Caused the Tripole Trend of Asian Precipitation During the Holocene

“…Shi and Yan (2019) found that the evolution of precipitation associated with the EASM, South ASM, and North African summer monsoon exhibited the characteristic of hemispheric synchrony since the LGM, and that Asian-African summer monsoonal precipitation generally increased between the LGM and 10 Kyr BP and then decreased subsequently. It is generally considered that such orbital-scale climatic changes over monsoonal Asia were predominantly caused by orbital-induced variation in insolation (Cheng et al, 2020;Lu et al, 2019). In addition, proxy records and TraCE-21ka simulations both revealed a Holocene wetting tendency in ACA (F. Chen et al, 2008Chen et al, , 2016.…”