Sea ice pressure ridge statistics of the Barents Sea and Fram Strait from ICESat-2 laser altimetry observations during 2018-2022

Abstract The variability of ice thickness in the Barents Sea is poorly described, with irregular import events of deformed ice intrusions with strong spatial and temporal variability. In contrast, the primary export of sea ice from the Arctic Ocean occurs through the Fram Strait where most sea ice studies have been performed. Here, we present sea ice pressure ridge statistics for the Fram Strait and Barents Sea derived from high-resolution surface topography information from NASA’s laser altimeter, ICESat-2, acquired during the period 2018–2022. These ICESat-2-derived statistics are compared against keel draft ridge statistics derived from moored upward looking sonars (ULS)using established keel-to-sail-ratios from literature. Ridges are identified using two detection thresholds (0.6 or 0.2 m above local ice elevation). Using 0.2 m, sail heights in the Barents Sea are ~34% smaller than the Fram Strait. In comparison, a 0.6 m threshold observes sail heights in the Barents Sea being 85% of those in the Fram Strait. Of individual ridges on basin scales, 1140–2658% more ridges were observed by ICESat-2 compared to ridges identified at the moored stations. Comparison with ULS-derived statistics shows comparable results when accounting for different detection thresholds (minimum sails/drafts) and reference levels (water or ice level); when unaccounted for, a difference of >1 m in median keel draft, depending on ratio used, is observed. More than 40% of the ICESat-2-detected ridges in the Fram Strait (using 0.6 mthreshold) had smaller estimated drafts than detectable with current methods applied to the ULS observations in the Fram Strait, high-lighting the importance of comparable reference levels.