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Fast Ice Thickness Distribution in the Western Ross Sea in Late Spring
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  • Patricia Jean Langhorne,
  • Christian Haas,
  • Daniel Price,
  • Wolfgang Rack,
  • Gregory H Leonard,
  • Gemma M. Brett,
  • Stefano Urbini
Patricia Jean Langhorne
University of Otago
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Christian Haas
AWI
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Daniel Price
University of Canterbury
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Wolfgang Rack
University of Canterbury, NZ
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Gregory H Leonard
National School of Surveying

Corresponding Author:[email protected]

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Gemma M. Brett
University of Canterbury
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Stefano Urbini
Istituto Nazionale di Geofisica e Vulcanologia
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Abstract

We present a 700 km airborne electromagnetic survey of late-spring fast ice and sub-ice platelet layer (SIPL) thickness distributions, from McMurdo Sound to Cape Adare, providing a first-time inventory of thickness close to its annual maximum. The overall modal consolidated ice (including snow) thickness was 1.9 m, less than its mean of 2.6±1.0 m. Our survey was partitioned into level and rough ice, and SIPL thickness was estimated under level ice. Although results show a prevalence of level ice, with a mode of 2.0 m and mean of 2.0±0.6 m, rough ice covered 41% of the transect by length, 50% by volume, with a mode of 3.3 m and mean of 3.2±1.2 m. The thickest 10% of rough ice was almost 6 m on average, and a 2 km segment in Moubray Bay had a thickness greater than 8 m, demonstrating the overwhelming influence of deformation against coastal features. The fast ice was thus significantly thicker than adjacent pack ice. The presence of a significant SIPL was observed in Silverfish Bay, offshore Hells Gate Ice Shelf, New Harbour, and Granite Harbour where the SIPL transect volume was a significant fraction (0.30) of the consolidated ice volume. The thickest 10% of SIPLs had an average thickness of nearly 3 m, and near Hells Gate Ice Shelf the SIPL was almost 10 m thick, implying vigorous heat loss to the ocean (~ 90Wm-2). We conclude that polynya-induced deformation and interaction with continental ice influence fast ice thickness in the western Ross Sea.