The Antarctic sea ice cover from ICESat-2 and CryoSat-2: freeboard, snow depth, and ice thickness
<p>We offer a view of the Antarctic sea ice cover from lidar (ICESat-2) and radar (CryoSat-2) altimetry, with retrievals of freeboard, snow depth, and ice thickness that span an 8-month winter between 1 April and 16 November 2019. Snow depths are from freeboard differences. The multiyear ice o...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-12-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/14/4453/2020/tc-14-4453-2020.pdf |
| Summary: | <p>We offer a view of the Antarctic sea ice cover from lidar
(ICESat-2) and radar (CryoSat-2) altimetry, with retrievals of freeboard,
snow depth, and ice thickness that span an 8-month winter between 1 April and 16 November 2019. Snow depths are from freeboard differences. The
multiyear ice observed in the West Weddell sector is the thickest, with a
mean sector thickness <span class="inline-formula">></span> 2 m. The thinnest ice is found near polynyas
(Ross Sea and Ronne Ice Shelf) where new ice areas are exported seaward and
entrained in the surrounding ice cover. For all months, the results suggest
that <span class="inline-formula">∼</span> 65 %–70 % of the total freeboard is comprised of snow.
The remarkable mechanical convergence in coastal Amundsen Sea, associated
with onshore winds, was captured by ICESat-2 and CryoSat-2. We observe a
corresponding correlated increase in freeboards, snow depth, and ice
thickness. While the spatial patterns in the freeboard, snow depth, and
thickness composites are as expected, the observed seasonality in these
variables is rather weak. This most likely results from competing processes
(snowfall, snow redistribution, snow and ice formation, ice deformation, and basal
growth and melt) that contribute to uncorrelated changes in the total and radar
freeboards. Evidence points to biases in CryoSat-2 estimates of ice
freeboard of at least a few centimeters from high salinity snow
(<span class="inline-formula">></span> 10) in the basal layer resulting in lower or higher snow
depth and 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 17 900–15 600 km<span class="inline-formula"><sup>3</sup></span> in October, for
an average thickness of <span class="inline-formula">∼</span> 1.29–1.13 m. Validation of Antarctic
sea ice parameters remains a challenge, as there are no seasonally and
regionally diverse data sets that could be used to assess these large-scale
satellite retrievals.</p> |
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| ISSN: | 1994-0416 1994-0424 |