Enhanced relationship between preceding autumn-winter sea ice over Greenland Sea and following Indian Summer Monsoon rainfall after early-2000s

The present study investigates the temporal variation in the connection between Arctic sea ice concentration (SIC) and Indian summer monsoon rainfall (ISMR) during 1980–2023. The ISMR shows an insignificant correlation with the preceding October–November–December–January (OND(−1)J(0)) Greenland Sea SIC (GSSIC) during 1980–2001, whereas the relationship turns to be significant positive during 2002–2023. During this latter period, the increasing GSSIC in preceding OND(−1)J(0) can exert wave trains that travel from North Atlantic to northeast Pacific, inducing anomalous anticyclone and cyclone over northeast of Hawaii and southwest of Mexico, respectively. This, in turn, generates a dipole sea surface temperature anomalies (SSTA) over northeast Pacific, with positive SSTA northeast of Hawaii and negative SSTA southwest of Mexico. The Wind-Evaporation-SST (WES) feedback helps maintain this dipole SSTA through to the following June–July–August–September, contributing to the negative SSTA over north central tropical Pacific (NCTP). The negative NCTP SSTA can induce anomalous ascending motion over the western Pacific–Indian Ocean by modulating Walker circulation, ultimately leading to increase ISMR. In contrast, during 1980–2001, GSSIC shows stronger co-variation with North Atlantic dipole (NAD) SSTA compared with that during 2002–2023. Due to the response of atmospheric circulation anomalies to the GSSIC are nearly opposite to those in terms of the NAD SSTA, the influence of the GSSIC anomalies on the wave trains over Northern Hemisphere is disturbed. Therefore, the GSSIC anomalies can slightly impact on the SSTA over northeast Pacific, resulting in weaker GSSIC-ISMR relationship.