Warm Atlantic water explains observed sea ice melt rates north of Svalbard

Abstract

Warm Atlantic water (AW) that flows northward along the Svalbard west coast is thought to transport enough heat to melt regional Arctic sea ice effectively. Despite this common assumption, quantitative requirements necessary for AW to directly melt sea ice fast enough under realistic winter conditions are still poorly constrained. Here we use meteorological data, satellite observations of sea ice concentration and drift, and model output to demonstrate that most of the sea ice entering the area over the Yermak Plateau melts within a few weeks. Simulations using the Los Alamos Sea Ice Model (CICE) in a 1‐D vertically resolved configuration under a relatively wide range of in situ observed atmospheric and ocean forcing show a good fit to observations. Simulations require high‐frequency atmospheric forcing data to accurately reproduce vertical heat fluxes between the ice or snow and the atmosphere. Moreover, we switched off hydrostatic equilibrium to properly reproduce ice and snow thickness when observations showed that ice had a negative freeboard, without surface flooding and snow‐ice formation. This modeling shows that realistic melt rates require a combination of warm near‐surface AW and storm‐induced ocean mixing. However, if AW is warmer than usual (>5°C), then lower mixing rates are sufficient. Our results suggest that increased winter storm frequency and increased heat content of the AW may work together in reducing future sea ice cover in the Eurasian basin.