4.4 The Role of Ocean Waves in the Opposing Antarctic Sea Ice Extent Trends

Tuesday, 24 January 2017: 11:15 AM
Conference Center: Skagit 3 (Washington State Convention Center )
Esther L. van Dijk, Victoria University Wellington, New Zealand, Wellington, New Zealand; and J. A. Renwick

Satellite observations since 1979 show a weak positive trend in the overall Antarctic sea ice extent. State-of-the-art sea ice models fail to reproduce these trends indicating limited understanding of processes influencing Antarctic sea ice. It has been argued that an important missing process in models are the interactions between ocean waves and sea ice. Depending on the ocean wave energy, waves can break up sea ice and attenuate through the ice pack for hundreds of kilometres. Here we investigate if the importance of ocean waves on sea ice trends can be inferred from observational data and ERA-Interim reanalysis data. We apply a variety of statistical exploratory techniques and multivariate techniques to investigate the relations between ocean waves, atmosphere and sea ice on interannual to decadal time scales. 
Our results indicate significant positive trends in the ocean wave height near the sea ice edge during the sea ice growth season in the Amundsen-Bellingshausen Seas, an area which experienced a sea ice decline over the last decades. Storm tracks could be contributing to the ocean wave height trends as results show significant positive correlations between storm track density and intensity and the ocean wave height at the Amundsen-Bellingshausen Seas. The opposite signal is found at the Ross Sea where sea ice has been increasing over the last decades. Here ocean waves show a small decrease in height and no trend in storm track density or intensity. We investigate the relative contribution of these wave and storm track trends on the regional sea ice trends and how they are related to changes in ocean wave directions around the sea edge and atmospheric circulation modes. These preliminary results support the hypothesis that ocean waves have an important impact on Antarctic sea ice trends as the increase of ocean wave height could increase the wave attenuation across the ice pack contributing to sea ice decline at the Bellingshausen/Amundsen Sea.
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