Impact of Sea Ice Over the Greenland Sea on the Indian Ocean Dipole Mode During Boreal Autumn

This study identifies a significant positive relationship between Indian Ocean dipole mode (IODM) and Greenland Sea sea ice concentration (GSSIC) in autumn during 1980–2023. The increasing GSSIC can lead to a vertical circulation cell anomaly between the polar region and middle latitude over the North Atlantic due to the thermal condition anomalies. The associated anomalous ascending flow over the coast of western Europe generates wave train propagating southeastward from mid-high latitude Atlantic to the North Indian Ocean (IO), causing anomalous anticyclone over the Indian Ocean. The related anomalous easterlies over tropical IO contribute to the positive IODM (warmer SSTA over west tropical IO but cooler SSTA off Sumatra–Java) through weakening the wind-evaporation-SST feedback over tropical IO and shallowing (deepening) thermocline along the coastal of Sumatra-Java (west tropical IO). Moreover, the numerical experiments can basically reproduce the observed mechanisms.