Oceanic Forcing of Arctic Sea Ice

The recent warming and dramatic summer reduction of sea ice cover in the Arctic Ocean so far have been primarily associated with the atmospheric forcing and ice-albedo feedback. We analyze numerical model output validated with available observations to determine the relative importance of the internal oceanic forcing of sea ice melt. In particular, the thermodynamic coupling at the ice-ocean interface in the western Arctic Ocean is investigated. Under-ice ablation by anomalously warm water advected from the Chukchi shelves and distributed at the subsurface layer in the western Arctic Ocean by mesoscale eddies is found to explain at least 60% of the total variance of sea ice thickness. We hypothesize that the excess oceanic heat, that in recent years has been accumulating below the surface during summer, is a critical initial factor in reducing ice concentration and thickness in the western Arctic Ocean at the early melting season and onwards the following year. Observational data and more realistic model representation of feedback processes between the upper ocean and the atmosphere under diminishing ice cover are critical to test this hypothesis and to advance Arctic climate prediction.