Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years
Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7 years
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DOI：
10.5194/tc-12-521-2018
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发表时间：
2018-02-13
期刊：
影响因子：
5.2
通讯作者：
Nilsson, Johan
中科院分区：
文献类型：
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作者：
Gardner, Alex S.;Moholdt, Geir;Nilsson, Johan
大冰盖的冰排放在决定海平面上升速度方面起着直接作用。我们使用Landsat 7号和8号图像绘制了目前整个南极地区2013-2015年的表面速度图，并与早先通过合成孔径雷达得出的估计值进行了比较，揭示了自2008年以来冰流的不均匀变化。新的地图提供了S以北82.4度以北的沿海和内陆冰速度的完整覆盖，平均误差为<；10m yr(-1)，这是由于白天获取的多个重叠图像对造成的。使用优化的通量门，2015年南极的冰流量为1929+/-40千兆吨/年(GT yr(-1))，比雷达测绘时增加了36+/-15GT yr(-1)。西南极阿蒙森海湾、盖兹冰架和位于南极半岛西部的玛格丽特湾的接地线上的水流加速，占这一增长的88%。相比之下，东南极冰盖的冰川在观测期间一直非常稳定。包括模拟的积雪和底部融化速度在内，南极冰盖在2008至2015年间的平均消融速度为183+/-94GT年(-1)。过去7年来，冰川流量的小幅增长与冰盖质量的高损失率和明显的海拔降低空间模式形成了鲜明的对比。西南极冰盖正在经历高质量损失率，并显示出明显的海拔下降模式，这表明存在动态不平衡。我们发现，在过去的7年里，冰的流量略有增加，这表明最近南极洲的质量损失模式是数十年来冰川流动增强的较长期阶段的一部分，该阶段始于第一个大陆范围的冰流雷达测绘。
Ice discharge from large ice sheets plays a direct role in determining rates of sea-level rise. We map present-day Antarctic-wide surface velocities using Landsat 7 and 8 imagery spanning 2013-2015 and compare to earlier estimates derived from synthetic aperture radar, revealing heterogeneous changes in ice flow since similar to 2008. The new mapping provides complete coastal and inland coverage of ice velocity north of 82.4 degrees S with a mean error of < 10 m yr(-1), resulting from multiple overlapping image pairs acquired during the daylight period. Using an optimized flux gate, ice discharge from Antarctica is 1929 +/- 40 Gigatons per year (Gt yr(-1)) in 2015, an increase of 36 +/- 15 Gt yr(-1) from the time of the radar mapping. Flow accelerations across the grounding lines of West Antarctica's Amundsen Sea Embayment, Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula, account for 88% of this increase. In contrast, glaciers draining the East Antarctic Ice Sheet have been remarkably constant over the period of observation. Including modeled rates of snow accumulation and basal melt, the Antarctic ice sheet lost ice at an average rate of 183 +/- 94 Gt yr(-1) between 2008 and 2015. The modest increase in ice discharge over the past 7 years is contrasted by high rates of ice sheet mass loss and distinct spatial patters of elevation lowering. The West Antarctic Ice Sheet is experiencing high rates of mass loss and displays distinct patterns of elevation lowering that point to a dynamic imbalance. We find modest increase in ice discharge over the past 7 years, which suggests that the recent pattern of mass loss in Antarctica is part of a longer-term phase of enhanced glacier flow initiated in the decades leading up to the first continent-wide radar mapping of ice flow.