Preprints
https://doi.org/10.5194/tc-2021-367
https://doi.org/10.5194/tc-2021-367

  06 Dec 2021

06 Dec 2021

Review status: this preprint is currently under review for the journal TC.

Altimetric observation of wave attenuation through the Antarctic marginal ice zone using ICESat-2

Jill Brouwer1,2, Alexander D. Fraser2, Damian J. Murphy3,2, Pat Wongpan2, Alberto Alberello4, Alison Kohout5, Chris Horvat6, Simon Wotherspoon1, Robert A. Massom3,2, Jessica Cartwright7, and Guy D. Williams1 Jill Brouwer et al.
  • 1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
  • 2Australian Antarctic Program Partnership, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
  • 3Australian Antarctic Division, Kingston, Australia
  • 4University of East Anglia, Norwich, United Kingdom
  • 5National Institute of Water and Atmospheric Research, Christchurch, New Zealand
  • 6Brown University, Providence, USA
  • 7Spire Global, Inc., Glasgow, United Kingdom

Abstract. The Antarctic marginal ice zone (MIZ) is a highly dynamic region where sea ice interacts with ocean surface waves generated in ice-free areas of the Southern Ocean. Improved large-scale (satellite-based) estimates of MIZ width and variability are crucial for understanding atmosphere-ice-ocean interactions and biological processes, and detection of change therein. Legacy methods for defining the MIZ width are typically based on sea ice concentration thresholds, and do not directly relate to the fundamental physical processes driving MIZ variability. To address this, new techniques have been developed to determine MIZ width based on the detection of waves and calculation of significant wave height attenuation from variations in ICESat-2 surface heights. The poleward MIZ limit (boundary) is defined as the location where significant wave height attenuation equals the estimated satellite height error. Extensive automated and manual acceptance/rejection criteria are employed to ensure confidence in MIZ width estimates, due to significant cloud contamination of ICESat-2 data or where wave attenuation was not observed. Analysis of 304 MIZ width estimates retrieved from four months of 2019 (February, May, September and December) revealed that sea ice concentration-derived MIZ width estimates were far narrower (by a factor of ~7) than those from the new techniques presented here. These results suggest that indirect methods of MIZ estimation based on sea ice concentration are insufficient for representing physical processes that define the MIZ. Improved measurements of MIZ width based on wave attenuation will play an important role in increasing our understanding of this complex sea ice zone.

Jill Brouwer et al.

Status: open (until 10 Feb 2022)

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Jill Brouwer et al.

Jill Brouwer et al.

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Short summary
The marginal ice zone is the region where ocean waves interact with sea ice. Although this important region influences many sea ice, ocean and biological processes, it has been difficult to accurately measure on a large scale from satellite instruments. We present new techniques for measuring the marginal ice zone extent using the NASA ICESat-2 laser altimeter. By measuring how waves attenuate within the sea ice, we show that the marginal ice zone may be far wider than previously realised.