格陵兰海海冰外缘线变化特征分析

格陵兰海作为北冰洋的边缘海之一,容纳了北极输出的海冰,其海冰外缘线的变化既受北极海冰输出量的影响,也受局地海冰融化和冻结过程的影响。利用2003年1月到2011年6月AMSR-E卫星亮温数据反演的海冰密集度产品,对格陵兰海海冰外缘线的变化特征进行了分析。结果表明,格陵兰海海冰外缘线不仅存在一年的变化周期,还存在比较显著的半年变化周期,与海冰在春秋两季向岸收缩有关。格陵兰海冬季的海冰外缘线极大值呈逐年下降的趋势,体现了北极增暖导致的冬季海冰范围减小;而夏季海冰外缘线离岸距离的极小值呈上升趋势,表明夏季来自北冰洋的海冰输出量增大。2003—2004年是格陵兰海夏季海冰融化最严重的2年。2007年北冰洋夏季海冰覆盖范围达到历史最小;而格陵兰海夏季的最小海冰范围最大,表明2007年北冰洋海冰的输出量大于其他年份。此外,夏季格陵兰岛冰雪融化形成的地表径流对海冰外缘线有一定的影响。对海冰外缘线影响最大的不是格陵兰海的局地风场,而是弗拉姆海峡(Fram Strait)区域的经向风,它直接驱动了北冰洋海冰向格陵兰海的输运,进而对格陵兰海海冰外缘线的分布产生滞后的影响。

Variability of the Greenland Sea Ice Edge

The Greenland Sea, a marginal sea of the Arctic Ocean, accommodates ice flux from the Arctic. The Greenland Sea ice edge is affected by ice export from the Arctic Ocean and also by local sea ice melting and freezing processes. The sea ice concentration product inverted from brightness temperature data on the AMSR-E microwave sensor from January 2003 to June 2011 is used to discuss the variability of the Greenland Sea ice edge in this paper. The study shows that the Greenland Sea ice edge did not only show annual periodic variations, but also significant semi annual periodic variations associated with sea ice extent changes in spring and autumn. The maximum of winter sea ice edge had a decreasing trend which demonstrated sea ice extent decreasing caused by Arctic warming in winter, and the minimum of summer sea ice edge had a increasing trend caused by higher sea ice export from Arctic Ocean in summer. 2003 and 2004 were the year Greenland Sea ice melt most in summer. In 2007, the Arctic Ocean had the largest ice extent, while the Greenland Sea had the least ice extent that demonstrated more ice export from Arctic Ocean than the other years. In addition, surface water runoff from ice melting in summer on the Greenland had a certain impact on the variability of sea ice edge. Meridional wind in Fram Strait, which drove ice transport from the Arctic Ocean to the Greenland Sea and then produced lagging effect on the distribution of the Greenland Sea ice edge, played a more important role than local wind field on ice edge variations.