Strengthened East Asian Winter Monsoon Regulated by Insolation and Arctic Sea Ice Since the Middle Holocene

The East Asian winter monsoon (EAWM) is a crucial climate system in Asia, with significant social and economic impacts. Orbital-scale variability of the EAWM during the Holocene and its associated mechanisms, however, are still not fully understood. Based on a high-resolution transient simulation by a coupled climate model, we present here a continuous climate evolution of the EAWM in response to orbital forcing. Our simulated springtime EAWM variations, consistent with grain size records of loess, exhibit an obvious strengthening trend since the mid-Holocene. In winter, a similar increasing trend is also simulated although not statistically significant. Our results suggest that the Holocene EAWM is basically controlled by meridional temperature gradients between high and low latitudes in both seasons. Other than northern insolation forcing, the feedbacks from Arctic sea ice and Eurasian snow cover also modulate the meridional temperature gradients, highlighting their important roles in driving EAWM evolution during the Holocene. Understanding the past climate change in the East Asian winter monsoon (EAWM) is necessary for assessing future climate scenarios in Asia. However, our current knowledge about the Holocene EAWM changes and associated mechanisms, based on geological proxies and numerical simulations, remains controversial, impeding understanding of the climate factors driving future EAWM change. In our study, we conducted a high-resolution transient simulation to investigate the evolution of EAWM. Our results reveal that the EAWM has been strengthening since the mid-Holocene, as evidenced by grain size records of loess. The EAWM during the Holocene is primarily influenced by meridional temperature gradients, rather than local temperature. More pronounced changes in Arctic ice cover can amplify the latitudinal temperature gradient between low and high latitudes via albedo feedback. These insights contribute to a better understanding of long-term climate variability in East Asia and its implications for projecting future climate change under anthropogenic warming scenario. Transient simulation reveals strengthened East Asian winter monsoon (EAWM) in both winter and spring since the mid-HoloceneThe EAWM during the Holocene is primarily influenced by meridional temperature gradients between high and low latitudesIn addition to northern insolation, feedbacks from Arctic sea ice and Eurasian snow cover also affect temperature structure