Enhanced Decadal Warming of the Southeast Indian Ocean During the Recent Global Surface Warming Slowdown

The rapid Indian Ocean warming during the early-21th century was a major heat sink for the recent global surface warming slowdown. Analysis of observational data and ocean model experiments reveals that during 2003-2012 more than half of the increased upper Indian Ocean heat content was concentrated in the southeast Indian Ocean (SEIO), causing a warming hot spot" of 0.8-1.2K decade(-1) near the west coast of Australia. This SEIO warming was primarily induced by the enhancements of the Pacific trade winds and Indonesian throughflow associated with the Interdecadal Pacific Oscillation's (IPO) transition to its negative phase, and to a lesser degree by local atmospheric forcing within the Indian Ocean. Large-ensemble climate model simulations suggest that this warming event was likely also exacerbated by anthropogenic forcing and thus unprecedentedly strong as compared to previous IPO transition periods. Climate model projections suggest an increasing possibility of such strong decadal warming in future.