Characteristic Geometry of Keels in Arctic Sea Ice Ridges

Abstract Deformation within and between sea ice floes creates pressure ridges, which compose a considerable volume fraction of the Arctic sea ice cover and complicate sea ice volume measurements. An important parameter for quantifying the ice volume contained in these deformation features is the keel shape. We use ice draft data collected by submarine sonar between 1960 and 2005 to classify keel geometry based on the cross‐sectional area, keel depth, and keel width to show that geometry varies with draft relative to the surrounding undeformed ice. Small, bummock‐sized features are more likely to be cusp‐shaped, while larger ridge keels are more likely trapezoids. This is consistent across decades, regions, and between first‐ and multi‐year ice. Though comparatively rare, the deepest keels (8 m) are more likely to be triangular or cusped with increasing maximum keel depth. These findings are valuable for quantifying the impact of sea ice ridging on volume retrievals.