Antarctic sea-ice thickness and volume estimates from ice charts between 1995 and 1998
Date
2015-10-01
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International Glaciological Society
Abstract
This work evaluates two distinct calculations of central tendency for sea-ice thickness and
quantifies the impact such calculations have on ice volume for the Southern Ocean. The first
calculation, area-weighted average thickness, is computed from polygonal ice features and then
upscaled to regions. The second calculation, integrated thickness, is a measure of the central value of
thickness categories tracked across different scales and subsequently summed to chosen regions. Both
methods yield the same result from one scale to the next, but subsequent scales develop diverging
solutions when distributions are strongly non-Gaussian. Data for this evaluation are sea-ice stage-ofdevelopment
records from US National Ice Center ice charts from 1995 to 1998, as proxy records of ice
thickness. Results show regionally integrated thickness exceeds area-weighted average thickness by as
much as 60% in summer with as few as five bins in thickness distribution. Year-round, the difference
between the two calculations yields volume differences consistently >10%. The largest discrepancies
arise due to bimodal distributions which are common in ice charts based on current subjective-analysis
protocols. We recommend that integrated distribution be used for regional-scale sea-ice thickness and
volume estimates from ice charts and encourage similar testing of other large-scale thickness data
archives.
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Citation
BERNSTEIN, E. Rachel, et al. "Antarctic sea-ice thickness and volume estimates from ice charts between 1995 and 1998." Annals of Glaciology 56.69 (2015): 383.