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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/tc-2020-145
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2020-145
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  12 Jun 2020

12 Jun 2020

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This preprint is currently under review for the journal TC.

The Antarctic sea ice cover from ICESat-2 and CryoSat-2: freeboard, snow depth and ice thickness

Sahra Kacimi and Ron Kwok Sahra Kacimi and Ron Kwok
  • Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA

Abstract. We offer a view of the Antarctic sea ice cover from lidar (ICESat-2) and radar (CryoSat-2) altimetry, with retrievals of freeboards, snow depth, and ice volume that span an 8-month winter between April 2019 and November 2019. Snow depths are from freeboard differences. The multiyear ice in the West Weddell sector stands out with a mean sector thickness > 2 m. Thinnest ice is found near polynyas (Ross Sea and Ronne) where new ice areas are exported seaward and entrained in the surrounding ice cover. For all months, the results suggest that ~ 60–70 % of the total freeboard is comprised of snow. The remarkable response of the ice cover to mechanical convergence in the coastal Amundsen Sea, associated with onshore winds, was captured in the correlated increase in local freeboards and thickness. While the spatial patterns in the freeboard, snow depth, and thickness composites are as expected, the observed seasonality in these variables is surprisingly weak likely attributable to competing processes (snowfall, snow redistribution, snow-ice formation, ice deformation, basal growth/melt) that contribute to uncorrelated changes in the total and radar freeboards. Broadly, evidence points to biases in CryoSat-2 freeboards of at least a few centimeters from high salinity snow (> 10 psu) in the basal layer resulting in lower/higher snow depth/ice thickness retrievals although the extent of these areas cannot be established in the current data set. Adjusting CryoSat-2 freeboards by 3/6 cm gives a circumpolar ice volume of 14,700/12,400 km3 in October, for an average thickness of ~ 1.09/0.93 m. Validation of Antarctic sea ice parameters remains a challenge, there are no seasonally and regionally diverse data sets that could be used to assess these large-scale satellite retrievals.

Sahra Kacimi and Ron Kwok

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Sahra Kacimi and Ron Kwok

Sahra Kacimi and Ron Kwok

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Latest update: 17 Sep 2020
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Short summary
Our current understanding of the Antarctic ice cover is largely informed by ice extent measurements from passive microwave sensors. These records, while useful, provide a limited picture of how the ice is responding to climate change. In this paper, we combine measurements from ICESat-2 and CryoSat-2 missions to assess snow depth and ice thickness of the Antarctic ice cover over an 8-months period (April through November 2019). The potential impact of salinity in the snow layer is discussed.
Our current understanding of the Antarctic ice cover is largely informed by ice extent...
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