北极拉普捷夫海海冰多年变化研究

STUDY ON MULTIYEAR VARIATIONS OF SEA ICE IN THE LAPTEV SEA OF THE ARCTIC OCEAN

拉普捷夫海是北冰洋的边缘海和冰源地,对北冰洋的海冰变化有重要影响。通过分析AMSR-E海冰密集度数据以及NECP-DOE的风场、温度场数据,结果表明拉普捷夫海海冰在2002—2011年经历了如下过程:重冰年(2002—2004)—过渡性质年份(2005—2006)—轻冰年(2007、2009—2011),即冰情由重向轻转变。研究结果也表明拉普捷夫海的冰情轻重与融冰期长短有较好的相关性,融冰期持续时间越短,冰情越重。4个参数,包括海冰距平指数、最小海冰覆盖率、积温、风驱动指数描述了拉普捷夫海的海冰多年变化过程。海冰距平指数是时间(3—11月)平均下的海冰覆盖率距平值,定量给出了各年冰情的轻重;最小海冰覆盖率是夏季海冰的极限情况,变化范围在0.45%—48.73%,发生时间为8月底至10月上旬。积温是上一个冬季气温积累对当年冰情的影响,结果表明积温是影响当年冰情轻重的主要因素。2008年的上一个冬季经历了异常低温,造成当年的异常重冰年。风驱动指数给出了风场对海冰覆盖率变化的短期影响,与同时期其他年份相比,2006年4月、2007年9月均出现了异常强北风,一定程度上造成了2006年融冰开始时间延后、2007年夏季最小海冰覆盖率的明显偏大。

The Laptev Sea is an important marginal sea and ice source region that has a significant influence on sea ice coverage in the Arctic Ocean. Multiyear variations of sea ice in the Laptev Sea over ten years （2002--2021 ） are studied by analyzing the Advanced Microwave Scanning Radiometer-Earth Observing System （AMSR-E） sea ice concentration, and National Centers for Environmental Prediction-Department of Energy （NCEP-DOE） wind and temperature data. Over the ten years, sea ice in the Laptev Sea underwent a change from heavy-ice to light-ice years. There was a strong relationship between ice condition and ice melt duration. That is, the longer that dura- tion, the lighter the ice condition. Four parameters are defined to describe the muhiyear variations of ice in the sea. These are indices of sea ice anomaly, minimum ratio of sea ice coverage, accumulated temperature and wind. Indices of sea ice anomaly are time-averaged （from March through November） values of sea ice coverage ratio that quantitatively express the ice condition. The minimum ratio of sea ice coverage shows the extreme condition of sea ice in summertime; this minimum ratio usually occurred between late August and early October, with magnitude 0. 45 % -48.73 %. Accumulated temperature, which represents the wintertime impact of atmospheric temperature, is the prime influence on ice conditions in a given year. The heavy-ice year of 2008 resulted from the very low temper- ature of the prior winter. Wind indices represent the short-term impact on sea ice coverage in the Laptev Sea from wind forcing. In contrast to the same period in other years, there was an anomaly of northerly wind in April 2006 and September 2007, which to some extent postponed the onset of ice melt in 2006 and caused a positive anomaly of sea ice coverage in summer 2007.