Preprints
https://doi.org/10.5194/tc-2020-222
https://doi.org/10.5194/tc-2020-222

  18 Aug 2020

18 Aug 2020

Review status: a revised version of this preprint was accepted for the journal TC and is expected to appear here in due course.

A lead-width distribution for Antarctic sea ice: a case study for the Weddell Sea with high resolution Sentinel-2 images

Marek Muchow1, Amelie U. Schmitt2, and Lars Kaleschke3 Marek Muchow et al.
  • 1Universität Hamburg, Bundesstr. 53, 20146 Hamburg, Germany
  • 2Universität Hamburg, Bundesstr. 55, 20146 Hamburg, Germany
  • 3Alfred-Wegener-Institut, Postfach 12 01 61, 27515 Bremerhaven, Germany

Abstract. We derive for the first time a statistical lead-width distribution for Antarctic sea ice using Weddell sea ice as a case study. Therefore, we transfer previous approaches for Arctic sea ice with a power law with a positive exponent (p(xwidth) xwidtha, a > 1) to Antarctic sea ice. We use 20 carefully selected cloud-free Copernicus Sentinel-2 images from November 2016 until February 2018, covering only the months from November to April. In doing so we compare exponents given in the literature for the Arctic sea ice, who do not agree with each other, to Antarctic sea ice.

To detect leads we create a sea ice surface type classification for the Sentinel-2 Level 1C data products, which are selected due to their high spatial resolution of 10 m. We apply two different fitting methods to the measured lead widths, which have been used in previous studies for Arctic sea ice. The first fitting method is a linear fit, while the second method is based on a maximum likelihood approach. Here, we use both methods for the same lead-width data set to observe differences in the calculated power law exponent.

To further investigate influences on the power law exponent, we define two different lead thresholds for open water and nilas. The influence of the lead threshold on the exponent is bigger for the linear fit than for the method based on the maximum likelihood approach. We show that the exponent of the lead-width distribution ranges between 1.16 to 1.41 depending on the applied fitting method and lead threshold. This exponent for the Weddell sea ice is smaller than the previously observed exponents for the Arctic sea ice.

Marek Muchow et al.

 
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Marek Muchow et al.

Marek Muchow et al.

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Short summary
Linear openings in sea ice, also called leads, occur with widths from meters to kilometres. We use satellite images with a resolution of 10 m to identify leads and measure their width. With that we investigate the frequency of leads with specific widths, since other studies have shown a dependency of heat exchange on the lead width. We are the first to address the sea ice lead-width distribution in the Weddell Sea, Antarctica.