Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt
Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt
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DOI：
10.5194/tc-9-197-2015
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发表时间：
2015-01-01
期刊：
影响因子：
5.2
通讯作者：
Reijmer, C. H.
中科院分区：
文献类型：
--
作者：
Dunse, T.;Schellenberger, T.;Reijmer, C. H.
冰川和冰盖造成的质量损失目前占观测到的全球海平面上升的三分之二，自20世纪90年代以来，随着极地地区强烈的大气变暖，这种情况有所加速。在这里，我们提出了连续的GPS测量和卫星合成孔径雷达为基础的速度图，从盆地3，最大的流域盆地的Austfonna冰帽，斯瓦尔巴群岛。我们的观测结果表明，表面融化和多年冰流加速之间有很强的联系。我们确定了一个水文热力学反馈，连续动员停滞的冰区，最初冻结到他们的床，从而促进快速的基础运动在不断扩大的面积。到2012年秋季，海洋终点站的连续不稳定性在盆地-3的激增中升级。2012年4月至2013年5月期间，由此产生的4.2 +/- 1.6 Gt a（-1）的冰山流量使整个冰盖的产犊损失增加了两倍。考虑到终端推进的海水位移，相关海平面上升贡献为7.2 +/- 2.6 Gt a（-1）。这一速率与整个斯瓦尔巴群岛2003-2008年期间的年度冰量损失相匹配，突出了动态质量损失对冰川质量平衡和海平面上升的重要性。表面融化的积极作用，即外部强迫，与以前的观点形成鲜明对比，冰川浪涌纯粹是内部动力学不稳定性。考虑到持续的气候变暖和表面融化的重要性不断上升，我们提出了一个潜在的影响，未来的稳定性的冰盖地区的水文热力学反馈，即在存在一个冷的边缘冰塞，限制快速排水的内陆冰。大规模动态不稳定的可能性，如冰盖的部分解体，在全球海平面上升预测中得到承认，但没有量化。
Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the polar regions. Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of Basin-3. The resulting iceberg discharge of 4.2 +/- 1.6 Gt a(-1) over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. With the seawater displacement by the terminus advance accounted for, the related sea-level rise contribution amounts to 7.2 +/- 2.6 Gt a(-1). This rate matches the annual ice-mass loss from the entire Svalbard archipelago over the period 2003-2008, highlighting the importance of dynamic mass loss for glacier mass balance and sea-level rise. The active role of surface melt, i.e. external forcing, contrasts with previous views of glacier surges as purely internal dynamic instabilities. Given sustained climatic warming and rising significance of surface melt, we propose a potential impact of the hydro-thermodynamic feedback on the future stability of ice-sheet regions, namely at the presence of a cold-based marginal ice plug that restricts fast drainage of inland ice. The possibility of large-scale dynamic instabilities such as the partial disintegration of ice sheets is acknowledged but not quantified in global projections of sea-level rise.