Reduction in Arctic sea ice amplifies the warming of the northern Indian Ocean

The sea surface temperature (SST) in the tropical Indian Ocean(IO) has experienced rapid warming over the past 40 years. The reason for this phenomenon is still debated. Our study suggests that the decrease in Arctic sea ice during winter can influence the warming of SST in the Northern Indian Ocean (NIO) through three main pathway including atmospheric circulation, western Pacific SST and Tibet Plateau land. Firstly, the reduction of Arctic sea ice can trigger atmospheric teleconnection wave trains and circulation anomalies from the North Atlantic to the NIO, leading to anticyclone anomaly in the Bay of Bengal(BOB) that increases thermal contribution by radiation warming, as well as cyclonic anomalies in the Arabian Sea(AS) that increases dynamic contribution by warm current transport. Secondly, the reduction of Arctic sea ice can induce a wave train propagating from the Arctic through Eurasia to the western Pacific, resulting in anticyclone anomalies and SST rise in the South China Sea, thus enhancing the dynamic contribution of heat transfer through the Indonesian through flow(ITF). Thirdly,Arctic sea ice can enhances cross-equatorial flow by inducing warm surface temperature of the Tibetan Plateau.These three pathways will still exist until 2045 in future SSP245 emission scenarios.This study establishes a connection between the Arctic and the tropical IO, expanding our understanding of the relationship between these regions.