Strong and highly variable push of ocean waves on Southern Ocean sea ice

Type Article
Date 2018-06
Language English
Author(s) Stopa Justin1, 2, Sutherland Peter1, Ardhuin FabriceORCID3
Affiliation(s) 1 : UBO, CNRS, LOPS, IRD,Inst Francais Rech Exploitat Mer IFREMER, F-29280 Plouzane, France.
2 : Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Dept Ocean Resources & Engn, Honolulu, HI 96822 USA.
Source Proceedings Of The National Academy Of Sciences Of The United States Of America (0027-8424) (Natl Acad Sciences), 2018-06 , Vol. 115 , N. 23 , P. 5861-5865
DOI 10.1073/pnas.1802011115
WOS© Times Cited 55
Keyword(s) wave-ice interaction, Southern Ocean marginal ice zone, wave radiation stress, Sentinel-1 SAR, synthetic aperture radar

Sea ice in the Southern Ocean has expanded over most of the past 20 y, but the decline in sea ice since 2016 has taken experts by surprise. This recent evolution highlights the poor performance of numerical models for predicting extent and thickness, which is due to our poor understanding of ice dynamics. Ocean waves are known to play an important role in ice break-up and formation. In addition, as ocean waves decay, they cause a stress that pushes the ice in the direction of wave propagation. This wave stress could not previously be quantified due to insufficient observations at large scales. Sentinel-1 synthetic aperture radars (SARs) provide high-resolution imagery from which wave height is measured year round encompassing Antarctica since 2014. Our estimates give an average wave stress that is comparable to the average wind stress acting over 50 km of sea ice. We further reveal highly variable half-decay distances ranging from 400 m to 700 km, and wave stresses from 0.01 to 1 Pa. We expect that this variability is related to ice properties and possibly different floe sizes and ice thicknesses. A strong feedback of waves on sea ice, via break-up and rafting, may be the cause of highly variable sea-ice properties.

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