Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics Geophysical Research Letters

The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss. Plain Language Summary The effect of projected Arctic sea ice loss on the global climate system is investigated using a state-of-the-art coupled climate model. This study shows that the tropics respond to the ice loss within two to three decades via dynamical ocean processes and air-sea interaction. This tropical response in turn modifies the atmospheric circulation and precipitation responses over the North Pacific. This fast response indicates that ocean dynamics needs to be represented for an accurate picture of the global impact of Arctic sea ice loss.