Possible Influence of the Preceding October Sea Ice Over the Greenland Sea on the Indian Summer Monsoon Rainfall

The present study investigates the possible impact of Greenland Sea ice concentration (SIC) on the Indian summer monsoon rainfall (ISMR) and associated mechanisms. The results show that there is a significant positive relationship between ISMR and the preceding October Greenland Sea SIC (GSSIC), and the sea surface temperature anomalies (SSTA) in the north central tropical Pacific (NCTP) serve as the bridge that connects them during 1981–2023. Further analyses suggest that the increasing GSSIC can generate two branches of wave trains. One propagates over the high latitude mainly through the destructive interference with wavenumber-3, while the other propagates over mid-high latitude primarily through the destructive interference with wavenumber-4. These pathways lead to anomalous cyclones over the Bering Sea–Alaska and northern North America, anticyclones over northeast Hawaii, resulting in negative SSTA over northeast-east tropical Pacific from the preceding October to subsequent January. This SSTA can persist and intensify from February to September through Wind-Evaporation-Sea Surface Temperature feedback. As a result, the negative summer NCTP SSTA can induce anomalous ascending motion over the western Pacific–Indian Ocean by modulating the Walker circulation cell, contributing to the increasing ISMR. Moreover, the numerical experiments using NCAR CAM5.3 can basically reproduce the observed mechanisms.