Tracing the heat signature of Atlantic water through the GIN seas and its impact on Arctic ice and climate

The northwards transport of heat through the North Atlantic Ocean is a crucial part of the present climate system. Ocean heat loss at high latitudes warms the atmosphere and cryosphere, influencing weather and melting ice, while simultaneously contributing to deep water formation integral to the Atlantic Meridional Overturning Circulation. Farther north, rising temperatures influenced by this oceanic heat transport has also driven Arctic atlantification.  Thus accurate knowledge of ocean heat transport pathways will enable us to identify the hotspots of air-sea heat loss, and investigate the drivers of variability in heat transported along these pathways.   When defining the heat transport pathways through the North Atlantic, many studies primarily take into account surface level variables, such as sea surface temperature, surface currents, or sea surface height. We investigate the utility of ocean heat content integrated from level of deep convection, 1000m depth, in identifying the heat transport pathways within the subpolar North Atlantic. This study uses data from the GLORYS12V1 Global Reanalysis dataset, spanning a 28 year period, to demonstrate that a dimensionless product of heat content and current speed provides a heat transport proxy that is more effective in determining the key pathways than using either heat content or speed alone. As expected, this method reveals that the poleward oceanic heat transport primarily follows topography northwards, but also indicates the presence of returning flows and recirculations that comprise the larger heat transport pathway system. Using data from the ERA5 Climate Reanalysis dataset over the same time period, we also show that the regions of the Arctic that exhibit the greatest rate of near-surface atmospheric warming do not perfectly correspond with the pathways themselves, but can be seen to correlate with the trends in heat content in the water column. This implies that atmospheric models that rely only on SST without taking water column stratification and heat content into account may be underestimating ocean heat fluxes.