Future Evolution of Subpolar Atlantic and Arctic Ocean-Atmosphere Interaction in the CANARI Large Ensemble

The subpolar North Atlantic Ocean and adjacent Arctic Seas experience strong winter heat loss and surface water densification which play a key role in the large-scale ocean circulation. The balance of processes driving this heat loss is expected to change as the climate system heats up and ice cover declines with impacts on both the ocean and the atmosphere. Here, we use a 40-member ensemble of runs with the HadGEM3-GC3.1 model (termed the CANARI Large Ensemble) to investigate these changes. The runs span 1950-2014 and 2015-2100 using CMIP6 historical and SSP3-7.0 forcings, and model resolution is ¼ degree ocean – N216 atmosphere. In the sub-polar Atlantic, the winter heat loss initially strengthens through to the mid-1980s before weakening by of order 50% by 2100 due primarily to variations in the sea-air temperature gradient. In the Arctic, the winter heat loss is initially dominated by ice decline before becoming dominated by atmospheric conditions from mid-century onwards. Regional variations in the impacts of these changes on both the ocean and the atmosphere will also be explored.