National Institute of Water and Atmospheric Research, Christchurch 8011, New Zealand.
National Institute of Water and Atmospheric Research, Wellington 6021, New Zealand.
Nature. 2014 May 29;509(7502):604-7. doi: 10.1038/nature13262.
The propagation of large, storm-generated waves through sea ice has so far not been measured, limiting our understanding of how ocean waves break sea ice. Without improved knowledge of ice breakup, we are unable to understand recent changes, or predict future changes, in Arctic and Antarctic sea ice. Here we show that storm-generated ocean waves propagating through Antarctic sea ice are able to transport enough energy to break sea ice hundreds of kilometres from the ice edge. Our results, which are based on concurrent observations at multiple locations, establish that large waves break sea ice much farther from the ice edge than would be predicted by the commonly assumed exponential decay. We observed the wave height decay to be almost linear for large waves--those with a significant wave height greater than three metres--and to be exponential only for small waves. This implies a more prominent role for large ocean waves in sea-ice breakup and retreat than previously thought. We examine the wider relevance of this by comparing observed Antarctic sea-ice edge positions with changes in modelled significant wave heights for the Southern Ocean between 1997 and 2009, and find that the retreat and expansion of the sea-ice edge correlate with mean significant wave height increases and decreases, respectively. This includes capturing the spatial variability in sea-ice trends found in the Ross and Amundsen-Bellingshausen seas. Climate models fail to capture recent changes in sea ice in both polar regions. Our results suggest that the incorporation of explicit or parameterized interactions between ocean waves and sea ice may resolve this problem.
大风暴生成的波浪在海冰中传播的情况迄今尚未测量过，这限制了我们对海洋波浪如何使海冰破裂的理解。如果不了解更多关于海冰破裂的知识，我们就无法理解北极和南极海冰的近期变化，也无法预测未来的变化。在这里，我们表明，在南极海冰中传播的风暴生成的海洋波浪能够传输足够的能量，使海冰在距离冰缘数百公里的地方破裂。我们的结果是基于多个地点的同时观测，这些结果表明，大波浪使海冰破裂的位置比通常假设的指数衰减所预测的要远得多。我们发现，对于大波浪——波高大于三米的波浪——波高衰减几乎呈线性，而对于小波浪，则呈指数衰减。这意味着大海洋波浪在海冰破裂和后退中的作用比以前认为的更为重要。我们通过将观测到的南极海冰边缘位置与 1997 年至 2009 年间南大洋模型中显著波高的变化进行比较，来检验这种情况的更广泛的相关性，发现海冰边缘的退缩和扩张分别与平均显著波高的增加和减少相关。这包括捕获了罗斯海和阿蒙森-别林斯高晋海发现的海冰趋势的空间变化。气候模型未能捕捉到两个极地地区的近期海冰变化。我们的结果表明，将海洋波浪与海冰之间的显式或参数化相互作用纳入其中，可能会解决这个问题。
