Spatial variation of East Asian winter monsoon evolution between northern and southern China since the last glacial maximum

Abstract

The East Asian winter monsoon (EAWM) is one of the most dynamic components of the global climate system. Although poorly understood, knowledge of long-term spatial differences in EAWM variability during the glacial–interglacial cycles is important for understanding the dynamic processes of the EAWM. We reconstructed the spatiotemporal characteristics of the EAWM since the last glacial maximum (LGM) using a comparison of proxy records and long-term transient simulations. A loess grain-size record from northern China (a sensitive EAWM proxy) and the sea surface temperature gradient of an EAWM index in sediments of the southern South China Sea were compared. The data–model comparison indicates pronounced spatial differences in EAWM evolution, with a weakened EAWM since the LGM in northern China but a strengthened EAWM from the LGM to the early Holocene, followed by a weakening trend, in southern China. The model results suggest that variations in the EAWM in northern China were driven mainly by changes in atmospheric carbon dioxide (CO2) concentration and Northern Hemisphere ice sheets, whereas orbital insolation and ice sheets were important drivers in southern China. We propose that the relative importance of insolation, ice sheets, and atmospheric CO2 for EAWM evolution varied spatially within East Asia.

Northern hemisphere ice sheet expansion intensified Asian aridification and the winter monsoon across the mid-Pleistocene transition

“…The expansion of Northern Hemisphere ice sheets between our SIS and LIS experiments better represents the ice volume changes across the MPT. Despite these model differences, both previous 82,84,86,[89][90][91] and our new simulations indicate that Northern Hemisphere ice sheet expansion was associated with Asian cooling, winter monsoon strengthening, and aridification. Simulations suggest that large ice sheets can also drive cooling and aridification in North China under the warmer Pliocene boundary conditions 92 .…”

“…Although our experiments employ LGM orography, vegetation, lakes, aerosol conditions, and orbital parameters, we adjusted CO 2 and CH 4 concentrations from LGM to early Pleistocene glacial values to better reflect MPT glacial greenhouse gas conditions 72 . Moreover, previous simulations examined Asian climate responses to the combined influences of global ice volume, orbital forcing, and greenhouse gas concentration changes from the LGM to Holocene, pre-industrial, or present day 83,84,[86][87][88] , yet the response to ice volume change by itself was poorly constrained 82,89 . In our experiments, only the Northern Hemisphere ice sheet extent is varied and other parameters (e.g., greenhouse gas and orbital forcing) are kept constant, which helps to improve understanding of how Asian (hydro-) climate responds exactly to Northern Hemisphere ice sheet expansion across the MPT.…”

Eurasian environmental dynamics and humans: interactions over different time scales

“…This study reinforces the previous view of a proximal sediment source for the PCSM loess deposits (Peng et al, 2018). Li et al (2021, this volume) provide a challenging view on the spatial variation of East Asian winter monsoon (EAWM) evolution between northern and southern China since the last glacial maximum. An EAWM proxy record using grain-size variations in the southern CLP was compared with the one using the sea surface temperature gradient in the South China Sea and results of long-term transient simulations.…”