The Antarctic coastal ocean heat budget is dominated by heat loss to land ice melt

Transport of warm Circumpolar Deep Water (CDW) across the Antarctic continental shelf break is the primary source of heat to Antarctica's marginal seas. Net heat supplied by CDW is ultimately lost to: (i) the ocean surface, either to the atmosphere or sea ice, or (ii) the ice sheet, by melting the base of ice shelves and calved icebergs. Ocean models often neglect the heat exchange needed to melt ice shelves and icebergs. Simulations presented here indicate that this omits the largest ocean heat sink on the Antarctic continental shelf, representing 60% of heat supplied across the shelf break. Suppressing this heat sink in simulations drives enhanced heat loss to the atmosphere through thinned sea ice cover as well as nonlocal reductions in heat supply to the continental shelf via sea ice–mediated stratification changes. These results highlight a source of climate model bias and clarify the dynamics of heat transport to Antarctic ice shelves.