利用海冰密集度数据分析北极冰间湖变化

冰间湖内存在强烈的海-气相互作用和结冰析盐过程,在极区以及全球气候系统中起着重要作用。本文基于数字图像处理技术,从AMSR-E高分辨卫星遥感海冰密集度数据中提取了长时间序列的冰间湖变化信息,研究北极冰间湖内的净水面积、净水表面的净热通量(向上为正)、产冰量和产盐量的季节和年际变化,比较不同冰间湖区域之间的差异。研究结果表明:总净水面积分别在结冰初期和末期存在极大值,而由于总净水面积季节变化幅度不是很大,总产冰量和产盐量的季节变化主要受净热通量影响,在1月份存在极大值;在不同冰间湖区域内净水面积的季节变化中,进入结冰期越早的冰间湖内净水面积越快达到首次极大值;净热通量的年际变化趋势总体上是减小的,总净水面积是增加大的,其中靠近太平洋和大西洋入流口的冰间湖内净热通量减小的速率要比其他区域快,靠近亚欧大陆的冰间湖内净水面积增长速率要比其他区域大;总产冰量的年际变化同总净水面积基本一致,也是呈增加趋势。最后通过研究冰间湖的年际变化信息同海冰范围变化的相关性,发现如果连续多年冰间湖内年平均净热通量为负的异常,那么海冰范围将出现一次极小值。

STUDY OF THE VARIABILITY OF POLYNYAS IN THE ARCTIC BASED ON THE AMSR-E SEA ICE CONCENTRATION

Arctic polynyas are significant areas for ocean–atmosphere heat exchange, high winter sea ice production with resulting brine rejection, and play a critical role in local and regional climate variability. In the study, the net water area in Arctic polynyas is obtained through the image-processing technology, and the the net heat flux and the sea ice production in the surface of the net water are also estimated. Their seasonal and interannual variabilities are analyzed. Then, the Arctic is divided into the eight domains. The difference of the variabilities in different domains is studied. The result shows that the total net water area exists two maximums at the beginning and end of freezing time, respectively, and the total ice and salinity production are manily affected by the net heat flux and have a maximum on January. It is found that the times when the net water areas arrive first maximums are related to the times when polynyas starte freezing by analyzing the seasonal variabilities of the net water areas in different polynya domains. In the interannual variability, the net heat flux has a decreading trend and the net water area has a increasing trend, as a whole. The interannual variability of total ice production is very silmilar to that of the total net water area, and has also a increasing trend. At last, the correlation of the interannual variability bewteen sea ice extent and the anuual mean net heat flux in all polynyas is discussed.