Author(s): Cathleen Geiger; Jackie Richter-Menge; Tracy Deliberty; Bruce Elder; Jennifer Hutchings; Amanda Lawson; Joao Rodrigues; Nicholas Toberg; Peter Wadhams
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Abstract: We examine the variability of sea ice thickness distribution from the 20 km x 20 km nested UK submarine survey taken on 18 March 2007 in the Beaufort Sea. The survey is centered about a U. S. Navy ice camp. From 1-7 April 2007, two weeks later, a ground survey team measured the snow and ice thickness within a 2 km circle of the ice camp during an NSF-sponsored science program. Because sea ice drifts, the ice camp was additionally equipped with a GPS buoy to provide a Lagrangian reference reporting position continuously from 15March to 15 April. Results include a draft-to-thickness conversion ratio of 1.27 (including snow load effects) using a statistical mode matching algorithm. We find a mean of 2.99m for the ground survey and 3.07±0.21m (average and range) for 2 km incremental scales of the submarine survey relative to the camp. When truncating all submarine survey subsets to the8m limit of the ground survey, we find even closer agreement (2.95±0.20m). The range of mean thicknesses over all scales is less than instrument uncertainties. This leads to the conclusion that the mean thickness is nearly scale invariant in support of modeling assumptions using a continuum approach with grid cell resolutions from 2–20 km. The largest differences between scales are variations in relative amounts of deformed ice withlevel-to-slightly deformed first-year ice dominating near the camp. Beyond the camp, we find increased proportions of new ice, associated deformation, and deformation of thick first-year and multi-year ice categories. The result is an increased skewing, broadening, and flattening of the thickness distribution away from the strong narrow peak found close to the camp. Hence while the mean thickness is does not change over these scales, the thickness distribution does, and this difference may have a fundamental impact on modeling calculations, especially heat fluxes, material behavior, momentum fluxes, and certainly local biogeochemical interactions.
Year: 2010