Buoyancy Forcing Dominates the Cross-Equatorial Ocean Heat Transport Response to Northern Hemisphere Extratropical Cooling

Abstract Cross-equatorial ocean heat transport (OHT) changes have been found to damp meridional shifts of the intertropical convergence zone (ITCZ) induced by hemispheric asymmetries in radiative forcing. Zonal-mean energy theories and idealized model simulations suggested that these OHT occur primarily due wind-driven Indo-Pacific’s shallow subtropical cells (STCs) buoyancy-driven deep Atlantic overturning circulation (AMOC). In this study we explore partitioning between buoyancy momentum forcing ocean’s response. We adjust top-of-atmosphere solar cool Northern Hemisphere (NH) extratropics a novel set comprehensive climate designed isolate buoyancy-forced momentum-forced changes. case NH high-latitude forcing, confirm AMOC dominate Atlantic. However, contrast with prior expectations, STCs are primary driver Indo-Pacific. find Indo-Pacific STC nearly 4 times amount across equator as shallower This response arises from extratropical density perturbations amplified low cloud feedback communicated tropics ventilated thermocline. While specific is dependent on scheme, our results suggest total into provides basin-specific insight key aspects how damps ITCZ migrations previous zonal-mean frameworks omit.