"Impacts of Indian Ocean Warming on the Atlantic Ocean Circulation and Climate"

Abstract:

The tropical Indian Ocean (TIO) has warmed by 1°C since the 1950s, at a faster rate than the
other tropical oceans. In this talk, I will discuss how this warming can affect the Atlantic Ocean
via atmospheric and oceanic teleconnections. Specifically, by reorganizing the atmospheric
Walker circulation in the equatorial band, this warming can reduce precipitation in the tropical
Atlantic, resulting in pronounced surface salinity anomalies. On multidecadal timescales, these
anomalies are advected to northern high latitudes and strengthen the Atlantic meridional
overturning circulation (AMOC). The resultant AMOC changes lead to a stronger hemispheric
asymmetry and a northward shifted intertropical convergence zone (ITCZ). On shorter
timescales, Indian Ocean warming generates a train of atmospheric planetary waves, which reach
the subpolar North Atlantic, strengthen surface westerly winds there, and cool the underlying
ocean within a few months to years. This mechanism could potentially explain the suppressed
warming in the subpolar North Atlantic (known as the "warming hole") seen in the observational
record. Further, I will discuss the implications for past and future climate changes and ocean
interbasin teleconnections.