Observations of preferential summer melt of Arctic sea-ice ridge keels from repeated multibeam sonar surveys

• Main Authors: Salganik, Evgenii, Lange, Benjamin Allen, Katlein, Christian, Matero, Ilkka, Anhaus, Philipp, Muilwijk, Morven, Høyland, Knut Vilhelm, Granskog, Mats Anders
• Format: Text
• Language: English
• Published: 2023
• Subjects: Arctic; ice pack; Sea ice
• Online Access: https://doi.org/10.5194/tc-2023-106; https://tc.copernicus.org/preprints/tc-2023-106/

Sea-ice ridges constitute a large fraction of the total Arctic sea-ice area (up to 40–50 %); nevertheless, they are the least studied part of the Arctic ice pack. Here we investigate sea-ice melt rates using rare repeated underwater multibeam sonar surveys that cover a period of one month during the advanced stage of sea-ice melt. 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, 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. We investigated the Arctic first-year ice ridge with a 4.6 m average keel draft, 42 m width, and 4 % macroporosity. While bottom melt rates of ridge keel were 4 times higher than first-year level ice, surface melt rates were almost identical and responsible for 40 % of ridge draft decrease. We show high spatial variability of ridge keel cross-sectional melt ranging from 0.2 m to 2.6 m with the maximum point ice loss of 6 m. We attribute 57 % of the ridge total melt variability to keel draft (36 %), slope (32 %), and width (27 %), with higher melt for ridges with larger draft, steeper slope, and smaller width. The melt rate of ridge keel flanks was proportional to the draft, while there was increased keel melt within 10 m of its bottom corners, and the melt rates of the keel bottom were comparable to level ice melt.