Preferential Summer Melt of Deeper Ridge Keels in the Central Arctic Ocean from Multibeam Sonar Data

Sea-ice ridges constitute a large fraction of the total Arctic sea-ice volume (up to 40%); nevertheless, they are the least studied part of the Arctic ice pack. Here we investigate sea-ice melt rates using rare underwater multibeam data that cover a period of one month during the advanced melt stage in the Arctic summer. We show that the degree of bottom melt increases with ice draft for first-year and second-year level ice, and a first-year ice ridge keel, with an average of 0.45 m, 0.55 m, and 0.95 m of total snow and ice melt in the observation period, respectively. While bottom melt rates of ridge keels are 3-4 times higher than first-year level ice, surface melt rates are almost identical. Our estimate attributes 57% of the ridge keel melt variability to keel draft (36%), slope (32%), and width (27%).