2013和2012年夏季格陵兰岛冰盖表面融化对比及可能的影响机理分析  

Comparison of 2013 and 2012 Greenland Ice Sheet Surface Melt and Associated Mechanisms

作　　者：陈志强[1,2] 刘骥平[2] 范广洲[1] 胡永云[3] 

机构地区：[1]成都信息工程学院大气科学学院,成都610225 [2]中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室,北京100029 [3]北京大学物理学院大气与海洋科学系气候与海-气实验室,北京100871

出　　处：《大气科学》2015年第4期757-766,共10页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金项目41176169;国家重点基础研究发展计划(973计划)项目2011CB309704

摘　　要：本文重点分析了2013年夏季格陵兰冰盖表面的融化特征,并将2013年与2012年融化极值年的异常进行对比,探讨二者之间存在的动力和热力差异及其对冰盖表面融化的影响和机制。结果表明:2013年夏季格陵兰冰盖表面最大融化范围仅为44%,远小于2012年的97%,持续的时间也比2012年短20天左右,平均的融化面积和持续时间都接近气候平均态。2013年夏季大气环流异常与2012年近乎完全相反,格陵兰及附近海域为低压异常,500 h Pa位势高度场为负异常,大气环流和2012年相比更具有纬向型。格陵兰岛的北部和南部出现气旋异常,有利于输送北极的冷空气到格陵兰岛,不仅降低了夏季格陵兰冰盖表面的平均温度,而且也减少了格陵兰高温事件发生的频率。同时,2013年夏季格陵兰表面向下的辐射通量异常分布大体上呈西南—东北走向,不同于2012年的南北分布。尽管从分布上看,总的向下辐射通量以正的短波分量为主,但是长短波分量相互抵消使得2013年夏季总的向下辐射通量接近气候平均态,这使得辐射对冰盖表面温度的影响不明显。大气环流的动力和表面辐射收支的热力共同作用导致2013年夏季格陵兰冰盖表面融化经历了相对缓和的一年。In this study,we describe the characteristics of the Greenland Ice Sheet surface melt occurring in summer 2013 and compare the results with anomalies of the record surface melt observed in summer 2012.We then investigate the dynamic and thermodynamic differences between these two cases and their impacts on the Greenland Ice Sheet surface melt.Results show that the maximum surface melt extent was only 44％ in 2013,which is far less than 97％ as observed in 2012.The averaged extent and duration of the surface melt in 2013 were close to the climatology and 20 days shorter than that of 2012.The summer atmospheric circulation anomalies in 2013 were nearly opposite those observed in 2012.Greenland and the surrounding areas showed anomalously low pressure,particularly a negative height at 500 hPa,which led to a more zonal pattern than those observed in 2012.The corresponding anomalous cyclonic circulation in the north and south areas of Greenland was favorable for advecting cold Arctic air to Greenland.This phenomenon decreased the mean surface temperature and the frequency of extreme heat event over Greenland.Moreover,the surface downward radiation pattern in 2013 was oriented in a southwest-northeast direction over Greenland,which differs from the north-south distribution in 2012.The net downward radiation was small due to the cancellation of downward shortwave and longwave components in 2013.However,downward shortwave dominated from the distribution perspective,leading to an insignificant impact on surface temperatures over Greenland.The combination of dynamic effects of atmospheric circulation change and thermodynamic effects of the radiation budget contributed to the surface melt of the Greenland Ice Sheet with values close to climatology.

关 键 词：格陵兰岛冰盖 表面融化 大气环流 辐射收支 

分 类 号：P446[天文地球—大气科学及气象学]