TCD The Cryosphere Discussions TCD 1994-0440 Copernicus GmbH Göttingen, Germany 10.5194/tcd-7-441-2013 A combined approach of remote sensing and airborne electromagnetics to determine the volume of polynya sea ice in the Laptev Sea Rabenstein L. 1 Krumpen T. 2 Hendricks S. 2 Koeberle C. 2 Haas C. 3 Hoelemann J. A. 2 Institute of Geophysics, Swiss Federal Institute of Technology, Zurich, Switzerland Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany Department of Earth and Space Science and Engineering, York University, Toronto, Canada 01 02 2013 7 1 441 473 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.the-cryosphere-discuss.net/7/441/2013/tcd-7-441-2013.html The full text article is available as a PDF file from http://www.the-cryosphere-discuss.net/7/441/2013/tcd-7-441-2013.pdf

A combined interpretation of synthetic aperture radar (SAR) satellite images and helicopter electromagnetic (HEM) sea-ice thickness data has provided an estimate of sea-ice volume formed in Laptev Sea polynyas during the winter of 2007/08. The evolution of the surveyed sea-ice areas, which were formed between late December 2007 and middle April 2008, was tracked using a series of SAR images with a sampling interval of 2–3 days. Approximately 160 km of HEM data recorded in April 2008 provided sea-ice thicknesses along profiles that transected sea-ice varying in age from 1–116 days. For the volume estimates, thickness information along the HEM profiles was extrapolated to zones of the same age. The error of areal mean thickness information was estimated to be between 0.2 m for younger ice and up to 1.55 m for older ice, with the primary error source being the spatially limited HEM coverage. Our results have demonstrated that the modal thicknesses and mean thicknesses of level ice correlated with the sea-ice age, but that varying dynamic and thermodynamic sea-ice growth conditions resulted in a rather heterogeneous sea-ice thickness distribution on scales of tens of kilometers. Taking all uncertainties into account, total sea-ice area and volume produced within the entire surveyed area were 52 650 km<sup>2</sup> and 93.6 &plusmn; 26.6 km<sup>3</sup>. The surveyed polynya contributed 2.0 &plusmn; 0.5% of the sea-ice produced throughout the Arctic during the 2007/08 winter. The SAR-HEM volume estimate compares well with the 112 km<sup>3</sup> ice production calculated with a high resolution ocean sea-ice model. Measured modal and mean-level ice thicknesses correlate with calculated freezing-degree-day thicknesses with a factor of 0.87–0.89, which was too low to justify the assumption of homogeneous thermodynamic growth conditions in the area, or indicates a strong dynamic thickening of level ice by rafting of even thicker ice.

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