Journal of Geophysical Research 116 (2011) C00E02; doi:10.1029/2011JC006982
Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects
Peter Wadhams (Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, U.K., and Laboratoire d'Océanographie de Villefranche, Université Pierre et Marie Curie, Villefranche-sur-Mer, France), Nick Hughes (Forecasting Division for Northern Norway, Norwegian Ice Service, Tromsø, Norway) and João Rodrigues (Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, U.K.)
Abstract
A transect of the Arctic Ocean by the British submarine Tireless in March 2007 enabled the thickness characteristics of the ice cover to be measured during the winter immediately preceding the exceptional retreat of summer 2007. In this paper we report on mean and modal drafts, probability density functions of draft, and the frequency and depth distribution of pressure ridges, and we compare results with those from an earlier submarine cruise in winter 2004 which covered part of the same area. In the region from north of Fram Strait to Ellesmere Island (about 85° N, 0–70° W) we find no change in mean drafts between 2004 and 2007 though there is a change in ice composition, with more ridging in 2007 but a lesser modal draft. This agrees with the observations of younger ice being driven toward Fram Strait in 2007. The region north of Ellesmere Island continues to be a “redoubt” containing more thick deformed multiyear ice than any other part of the transect. In the west the submarine profiled extensively under the SEDNA ice camp at 73° N 145° W. This is in the same location as the 1976 AIDJEX ice camp and a sonar survey done by a U.S. submarine in April 1976. We found that a large decrease in mean draft had occurred (32%) over 31 years and that in 2007 the SEDNA region contained the thinnest ice of any part of the Arctic surveyed by the submarine; this was a region from which the ice completely retreated during the subsequent summer of 2007.
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Received 21 January 2011; accepted 14 June 2011; published 27 September 2011.
Citation: (2011), Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects, J. Geophys. Res., 116, C00E02, doi:10.1029/2011JC006982
Key Points
- Measurement of sea ice thickness from the submarine during winters of 2004 and 2007
- More first-year ice in 2007 but similar overall mean ice thickness to 2004
- Ice thickness distribution obtained from region later ice free in summer 2007
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