2013年北极最小海冰范围比2012年增加的原因分析

Reasons for the increase minimum Arctic sea ice extent in 2013 compared with 2012

北极海冰范围从1979年有卫星观测资料以来呈现明显下降趋势,尤其是9月份。2012年9月北极海冰范围达到有观测记录以来的最小值,而2013年9月比2012年同期增加了60%。增加的区域主要在东西伯利亚海区、楚科奇海和波弗特海区。本文应用距平和经验模态分解方法,分析了美国国家冰雪数据中心的北极海冰卫星数据、欧洲预报中心的夏季底层大气环流数据和上层海洋的温度,指出2013年北极最小海冰范围比2012年在北冰洋太平洋扇区增加的原因,是由于表面气温(SAT)降低、海平面气压(SLP)升高、气旋式风场异常、表面空气中水汽含量(SH)降低以及海表面温度(SST)降低5个条件形成的冰-SAT、冰-SST和冰-汽(SH)3个正反馈机制共同作用造成的。

Satellite data since 1979 show that the monthly mean Arctic sea-ice extent has downward trends,with the largest trend in September. The Arctic sea-ice minimum extent is observed in September 2012. While the mini- mum Arctic sea-ice area in the following September 2013 increases 60o/00 compared with 2012. The sea-ice increase areas mainly locate in the Pacific section of Arctic Ocean： East Siberian Sea, Chukchi Sea, and Beaufort Sea. By using methods of climatological anomalies and Empirical Mode Decomposition, we investigated the Arctic sea-ice data from the National Snow and Ice Data Center, lower atmospheric circulation pattern and the upper-ocean from ERA- Interim data in summer to explain this sea-ice sharp increase phenomenon. Results show that the increasing of the Arctic sea ice in 2013 compared with 2012 is related to the following five conditions： the surface air temperature （SAT） decrease, sea level pressure （SLP） increase, the cyclonic anomaly of wind field, surface special humidity （SH） and surface sea temperature （SST） decrease. All these five favorable conditions for sea-ice increase are close- ly related with by the ice-SAT,ice-SST and ice-SH positive feedbacks in the Arctic Ocean.