Diverse Regional Sensitivity of Summer Precipitation in East Asia to Ice Volume, CO<sub>2</sub> and Astronomical Forcing
Anqi Lyu, Qiuzhen Yin, Michel Crucifix, Youbin Sun
Abstract
Abstract The relative influence of insolation, CO 2 , and ice sheets on the East Asian summer monsoon (EASM) is not well understood especially at regional scale. Here a Gaussian emulator based on simulations with HadCM3 is used to quantitatively assess how astronomical forcing, CO 2 , and northern hemisphere ice sheets affect the variation of the summer precipitation over the last 800 ky. Our results show that in the EASM domain north of 25°N, the variation of the summer precipitation is dominated by precession, leading to strong 23‐ky cycles, while the ice sheets only modulate the effect of insolation by influencing the land‐sea pressure gradient. In the southern part, ice sheets play a more important role, generating 100‐ky cycles, through influencing the latitude of the Intertropical Convergence Zone and the Hadley cell. Obliquity and CO 2 have little effect on the summer precipitation as compared to precession and ice sheets.