Ice melt from ocean warming in a global ultra-high resolution ocean/sea-ice model.

At the margins of the Greenland and Antarctic Ice Sheets (GrIS and AIS) and in the subsurface eastern Arctic, warming waters sourced from the open ocean at lower latitudes are enhancing ice melt. To explore these ocean/ice interactions, we configured an atmospheric reanalysis forced global ultra-high resolution ocean/sea-ice model where the horizontal grid mesh reduces from 8 km at the equator to 2 km at the poles (UH8to2). Land-ice melt was represented in both hemispheres. To investigate the sensitivity of the ocean circulation over the West Greenland continental shelf/slope and in the eastern Labrador Sea to meltwater perturbations from the GrIS, a suite of short UH8to2 simulations were branched off the control without meltwater. In the presence of meltwater, the West Greenland and West Greenland Coastal Currents are faster than when meltwater is absent. Relative to the control, cross-shelf fluxes of freshwater into the Labrador Sea increase in the Ekman layer when meltwater is released at the surface. When meltwater is distributed vertically over the top 200 m (to account for fjord mixing) enhanced baroclinic conversion/eddy formation occurs over the upper water column and cross-shelf fluxes are greater than the other two cases.

Linkages between subsurface Atlantic Water (AW) in the eastern Arctic and basal sea-ice melt for the near-present were examined in the UH8to2 and regional Arctic 1/25º HYCOM/CICE5. Both models show a pulse of warm AW entering the eastern Eurasian Basin where it separates into multiple branches characterized by an active sub-surface mesoscale eddy field. Winter mixed layers are deep in this region (up to ~80 m); isothermal doming by halocline anticyclonic eddies supply heat through mesoscale stirring into the adjacent mixed layer. Wintertime sea-ice basal melt and dynamic tendency maps show a melt signature and sea-ice reduction tendency under the AW path. Convective activity arising from the late fall freeze-up of sea-ice likely transports AW vertically into the surface waters and the vicinity of sea-ice.