Seasonally varying SST changes in the joining area of Asia and Indian-Pacific Ocean from boreal spring to summer

The seasonal evolution of the sea surface temperature (SST) in the joining area of Asia and Indian-Pacific Ocean (AIPO) has strong impacts on its surrounding areas. Greenhouse gas-induced global warming brings seasonally varying changes in SST in AIPO, the formation of which is not totally understood. Based on historical and SSP5-8.5 runs of 23 climate models in phase 6 of the Coupled Model Intercomparison Project, this study shows that the SST changes under global warming over AIPO have considerable seasonal variation from boreal spring to summer and their formation is related to different physical processes. The AIPO SST changes show distinct seasonal variations across two subregions: the eastern Indian Ocean (EIO) experiences more pronounced warming in April and May compared to the annual mean, while the EIO and equatorial western Pacific (EWP) exhibit weaker warming from June to August. In the EIO, the seasonal variation in the changes in evaporative damping effect dominates the seasonal variation in SST changes, due to the change in surface wind speed and climatological evaporative damping. Compared to other seasons, the stronger warming during June and July in the equatorial eastern Pacific causes a greater eastward shift of convective upward motion in the EWP. This results in reduced shortwave radiation and weaker warming over the EWP during these months.