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5. CRREL Report

Title:	Sea ice ridging over the Alaskan continental shelf
Authors:	National Oceanic and Atmospheric Administration. United States United States. Bureau of Land Management Tucker, W. B. Weeks, W. F. Frank, M. D.
Keywords:	Arctic Ocean Statistical models Extreme values Laser profilometry Ridges Sea ice
Publisher:	Cold Regions Research and Engineering Laboratory (U.S.) Engineer Research and Development Center (U.S.)
Series/Report no.:	CRREL report ; 79-8.
Description:	CRREL Report Abstract: Sea ice ridging statistics obtained from a series of laser surface roughness profiles are examined. Each set of profiles consists of six 200-km-long flight tracks oriented approximately perpendicular to the coastline of the Chukchi and Beaufort Seas. The landward ends of the profiles were located at Point Lay, Wainwright, Barrow, Lonely, Cross Island and Barter Island. The flights were made in February, April, August, and December 1976, and one additional profile was obtained north of Cross Island during March 1978. It was found that although there is a systematic variation in mean ridge height (h) with season (with the highest values occurring in late winter), there is no systematic spatial variation in h at a given time. The number of ridges/km (m) is also high during the late winter, with the highest values occurring in the Barter and Cross Island profiles. In most profiles, the ice 20 to 60 km from the coast is more highly deformed (higher m values) than the ice either nearer the coast or farther seaward. The Wadhams model for the distribution of ridge heights gives better agreement with observed values in the higher ridge categories than does the Hibler model. Estimates of the spatial recurrence frequency of large pressure ridges are made by using the Wadhams model and also by using an extreme value approach. In the latter, the distribution of the largest ridges per 20 km of laser track was found to be essentially normal. Wadhams' distribution consistently predicts slightly larger ridge sails than does the extreme value approach. The main factors currently limiting the accurate prediction of the temporal recurrence of large pressure ridges are limited knowledge of the drift of near-shore ice and data that would permit the assessment of year-to-year variability in m.
Rights:	Approved for public release; distribution is unlimited.
URI:	http://hdl.handle.net/11681/9015
Appears in Collections:	CRREL Report