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.