Deformation, warming and softening of Greenland's ice by refreezing meltwater
Deformation, warming and softening of Greenland's ice by refreezing meltwater
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DOI：
10.1038/ngeo2179
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发表时间：
2014-07-01
影响因子：
18.3
通讯作者：
Paden, John D.
中科院分区：
文献类型：
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作者：
Bell, Robin E.;Tinto, Kirsteen;Paden, John D.
大冰盖下的融水可以通过底部的润滑作用或融水重新冻结形成相对温暖的冰时的软化作用来影响冰的流动（1-3）。再冻结在南极洲东部产生了大的基底冰单位（4）。无气泡的基底冰单元也在格陵兰冰盖的边缘露出水面（5），但重新冻结的程度及其对格陵兰冰流动力学的影响尚不清楚。在这里，我们表明，融水的再冻结产生不同的基底冰单位整个北方格陵兰岛的厚度高达1,100米。我们比较航空重力数据与模拟重力异常显示，这些基本单位是冰。使用雷达数据，我们确定的单位，显着扰乱覆盖冰盖地层的程度。这些单元由再冻结的基底水组成，通常被来自降雪的严重变形的流冰所包围。我们绘制这些单位沿沿着冰盖边缘的表面融化是最大的水源，以及在内部的基础融化是唯一的水源。在彼得曼冰川下面，基底单元与浮冰舌中的快速流动和通道的开始相吻合。我们认为，再冻结的融水和周围的基底冰的变形变暖的格陵兰冰盖，修改冰柱的温度结构，影响冰流和接地线融化。
Meltwater beneath the large ice sheets can influence ice flow by lubrication at the base or by softening when meltwater refreezes to form relatively warm ice(1-3). Refreezing has produced large basal ice units in East Antarctica(4). Bubble-free basal ice units also outcrop at the edge of the Greenland ice sheet(5), but the extent of refreezing and its influence on Greenland's ice flow dynamics are unknown. Here we demonstrate that refreezing of meltwater produces distinct basal ice units throughout northern Greenland with thicknesses of up to 1,100 m. We compare airborne gravity data with modelled gravity anomalies to show that these basal units are ice. Using radar data we determine the extent of the units, which significantly disrupt the overlying ice sheet stratigraphy. The units consist of refrozen basal water commonly surrounded by heavily deformed meteoric ice derived from snowfall. We map these units along the ice sheet margins where surface melt is the largest source of water, as well as in the interior where basal melting is the only source of water. Beneath Petermann Glacier, basal units coincide with the onset of fast flow and channels in the floating ice tongue. We suggest that refreezing of meltwater and the resulting deformation of the surrounding basal ice warms the Greenland ice sheet, modifying the temperature structure of the ice column and influencing ice flow and grounding line melting.