楚科奇海阿拉斯加沿岸冰间湖的变化及其影响因素分析

利用2003—2011年AMSR-E(Advanced Microwave Scanning Radiometer-Earth Observing System)日平均海冰密集度数据,对楚科奇海阿拉斯加沿岸冰间湖进行了分析。针对冰间湖的特点,在阈值法的基础上,通过统计冰间湖出现的频率,限定冰间湖的最大范围,区分各个冰间湖。通过计算阿拉斯加沿岸冰间湖的面积,结合NCEP-DOE(National Centers for Environmental Prediction-Department of Energy)再分析风场数据和白令海峡潜标观测的温盐和海流数据,初步探讨冰间湖发生和发展的规律。为了排除海冰外缘区对判断冰间湖的影响,研究仅限于白令海峡完全冰封的1—4月,可得到以下结论:阿拉斯加西北沿岸海域每年冬季都会出现5个冰间湖,多数时间为紧靠大陆边缘的沿岸冰间湖,巴罗角附近海岸在3月和4月会出现位于沿岸固定冰之外的裂缝冰间湖。冰间湖面积每天都发生变化,表现出天气尺度的变化特征,经历长达数日的发展和消失的过程,与风场的转换有密切关系。离岸风有利于沿岸冰间湖的扩展,但是该海域1—4月的盛行风为东北风和北风,对于多数冰间湖而言为沿岸风,不利于冰间湖的形成,因而冰间湖有时消失长达数十日。在偏北风的影响下,太平洋入流对北部冰间湖几无作用,而对南部冰间湖的空间分布有着重要影响。

VARIATIONS INCOASTAL POLYNYAS IN THEALASKAN CHUKCHI SEA AND MAJOR INFLUENCE FACTORS

Using daily AMSR-E sea ice concentration data from 2003 to 2011, the area of Alaska Coastal Polynyas in the Chukchi Sea was studied. According to the characteristics of these polynyas, threshold method was proposed to identify each polynya. Frequency of polynyas occurrence was also used to delimit the maximum range of polynyas in the studied region. Based on the information extracted from Alaska Coastal Polynyas, the temporal and spatial variations and their major influence factors were studied. To eliminate the effect of the open sea on the identification of polynyas, the analysis was limited between January and April when Bering Strait was totally covered by sea ice. The following conclusions were drawn: Every winter, five polynyas will appear along the Alaska Coastal area and are almost parallel to the coastline. In addition to the typical coastal polynyas, flaw polynyas tend to appear off landfast ice in the vicinity of Barrow Point in late March and April. Daily changes in polynya areas were dominated on synoptic scale, which is further related to the wind directions. Seaward winds favored the formation of coastal polynyas, but since northeast and north winds prevail in the studied region, polynya sites are sometimes closed or diminished in extent for up to a few weeks. Under the effect of northerly winds, Pacific Inflow has virtually no effect on the northern polynyas but has an important influence on the spatial distribution of southern polynyas along Alaska coastal area.