利用EnviSat ASAR数据监测南极冰架崩解

利用欧洲环境卫星(EnviSat)所携带的先进合成孔径雷达(ASAR)数据高时间、高空间分辨率的特点,实现了全南极范围内冰架年崩解面积的高精度估算和崩解类型的解译。利用40期重复覆盖全南极海岸线的EnviSatASAR数据探测了冰架崩解的位置、类型和发生时间,统计分析了2005年8月到2011年8月连续6年南极冰架崩解频率和面积的时空变化。结果显示:(1)2005年—2011年平均崩解面积为2969.7km2,年崩解面积变化幅度较大,年崩解频率略呈下降的趋势;(2)南极冰架崩解主要发生1—3月,其中2月崩解最频繁;(3)东南极威尔克斯地区域是当前南极冰架崩解最活跃的区域,冰架罗斯、龙尼-菲尔希纳及埃默里等3大冰架很稳定且鲜有崩解发生,东南极毛德皇后地区域冰架相对稳定;(4)空间尺度小于100km2的崩解频率占到总频率的94.1%,忽略它们将导致南极年崩解面积低估20.7%—92.9%;(5)以内部冰川应力为主要驱动力的开裂型(Rift-opening)崩解较以外部大气和海洋因素为主要驱动力的融水型(Melt-related)崩解发生更为频繁,但是两者在量上的差异不大(约10%)。

Antarctic iceberg calving monitoring based on EnviSat ASAR images

Using full utilization of the high temporal and spatial resolution Environmental Satellite (EnviSat) Advanced Synthetic Aperture Radar (ASAR) data, we implemented a high-precision estimation of the annual calving area of Antarctic ice shelves, as well as an interpretation of the calving type. With EnviSat ASAR data which 40 times repeatedly covered the whole Antarctic coastline, we detected the location, type and occurrence time of iceberg calving events, and conducted statistical analysis on the temporal and spatial variation data with respect to the calving frequency and calving area of Antarctic ice shelves from August 2005 to August 2011. The results showed that (1) from 2005 to 2011, the mean annual calving area of Antarctica was 2969.7 km², with a large varying amplitude of annual calving area and a slight decrease of the annual calving frequency; (2) the calving events of Antarctic ice shelves mainly occur from January to March, and most frequently in February; (3) the Wilkes Land located in East Antarctica is currently the area where iceberg calving occurs most frequently. The three major ice shelves, Ross, Filchner-Ronne and Amery ice shelf, are stable and calving events are rare. Ice shelves in the Queen Maud Land located in East Antarctica is relatively stable; (4) the frequency of iceberg calving with special scale less than 100 km² accounts for 94.1% of total frequency, and ignoring them will lead to an underestimation of the annual calving area of Antarctic ice shelves by 20.7% to 92.9%; (5) the rift-opening calving (R-calving) whose main driving force is internal glacial stress is more frequent than the melt-related calving (M-calving) whose main driving force is the external atmospheric and oceanic factors, but the difference is not that large (about 10%).