Ice deformation near SHEBA

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Abstract
The deformation rate of sea ice is a key parameter for determining the evolution of the ice thickness distribution. It determines the rate of new ice formation through opening and the rate of ridging through closing and shear. An extensive suite of ground‐based and satellite‐based measurements of ice motion is used to construct a daily time series of the ice velocity and deformation in the vicinity of the Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp that is suitable for forcing a model of the ice thickness distribution. The velocity is interpolated to a square grid that remains centered on the camp, has a spacing of 25 km, is 400 km on a side, and is determined for a 371‐day period from 2 October 1997 to 7 October 1998. Velocity measurements from buoys, Advanced Very High Resolution Radiometer (AVHRR), Special Sensor Microwave/Imager (SSMI), and Radarsat Geophysical Processing System (RGPS) are merged using optimal interpolation and a Kalman filter approach. The deformation rate is taken directly from the RGPS measurements when available. The daily total deformation rate measured on a scale of 100 km near the camp averaged 2.21% d−1, and the standard deviation was 1.78% d−1. The divergence was positive in the early winter and negative through most of the spring and summer. There were two major opening/closing events, one in January and one at the end of July. The net divergence over the year was very near zero. The vorticity indicated a net rotation of 87° over the year, with the winter showing strong anticyclonic turning and the summer showing strong cyclonic turning.

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