基于海冰密集度遥感数据的波弗特海海冰时空变化研究

采用美国冰雪数据中心(NSIDC)的日尺度与月尺度海冰密集度数据,将海冰密集度为15%作为阈值确定海冰外缘线位置,提取波弗特海海域的海冰外缘线,计算波弗特海的海冰密集度、海冰范围与海冰面积,然后通过海冰范围与海冰外缘线的年际变化与季节变化来分析波弗特海海冰外缘线退缩的时空变化特征与趋势。实验结果表明,1978—2015年波弗特海的海冰密集度、海冰范围与海冰面积整体变化趋势一致,减少趋势显著。37年来,海冰密集度平均每年减少约0.3%,海冰范围平均每年减少3 235 km2,海冰面积平均每年减少5 084 km2。海冰密集度在1979—1996年无明显减少趋势,1996—2015年减少趋势明显。波弗特海海冰范围一般在9月达到最小值,在11月至次年5月维持在最大值(全冰覆盖状态);海冰面积一般在9月达到最小值,在12月或者1月达到最大值。海冰范围最小值出现时间有延迟的趋势,全冰覆盖状态具有起始时间越来越晚、终止时间越来越早、持续时间越来越短的趋势,平均持续天数为212 d。

Analysis of spatiotemporal variability of sea ice in the Beaufort Sea using passive microwave remote sensing data

Based on daily and monthly sea ice concentration data, obtained from the National Snow and Ice Data Center, the 15% sea ice concentration limit in the Beaufort Sea was used as a threshold to determine the location of the sea ice edge. After extracting the sea ice edge, we calculated the sea ice concentration, sea ice extent, and sea ice area. We then analyzed the spatiotemporal variabilities and trends of the retreat of the ice edge in the Beaufort Sea through interannual and seasonal changes. The results showed that sea ice concentration, sea ice extent, and sea ice area in the Beaufort Sea during 1978–2015 all had significant trends of reduction. During the study period, sea ice concentration decreased by an average of about 0.3%·a–1, sea ice extent decreased by an average of 3 235 km2·a–1, and sea ice area decreased by an average of 5 084 km2·a–1. Sea ice concentration during 1979–1996 showed no significant trend of decrease, although a trend of reduction was evident during 1996–2015. The sea ice extent in the Beaufort Sea is at its maximum between November and May (full ice coverage) and at its minimum in September. The sea ice area reaches its minimum in September and its maximum in December or January. The time of minimum sea ice extent appears to have become delayed. The state of total ice cover has tended to begin later, end earlier, and its duration (average: 212 d) has become shorter.