School of GeoSciences, University of Edinburgh, Edinburgh EH8 9XP, UK.
Université Savoie Mont-Blanc, Polytech Annecy-Chambéry, LISTIC, BP 80439, 74944 Annecy-le-Vieux cedex, France.
Nature. 2015 Oct 29;526(7575):692-5. doi: 10.1038/nature15722.
Ice flow along land-terminating margins of the Greenland Ice Sheet (GIS) varies considerably in response to fluctuating inputs of surface meltwater to the bed of the ice sheet. Such inputs lubricate the ice-bed interface, transiently speeding up the flow of ice. Greater melting results in faster ice motion during summer, but slower motion over the subsequent winter, owing to the evolution of an efficient drainage system that enables water to drain from regions of the ice-sheet bed that have a high basal water pressure. However, the impact of hydrodynamic coupling on ice motion over decadal timescales remains poorly constrained. Here we show that annual ice motion across an 8,000-km(2) land-terminating region of the west GIS margin, extending to 1,100 m above sea level, was 12% slower in 2007-14 compared with 1985-94, despite a 50% increase in surface meltwater production. Our findings suggest that, over these three decades, hydrodynamic coupling in this section of the ablation zone resulted in a net slowdown of ice motion (not a speed-up, as previously postulated). Increases in meltwater production from projected climate warming may therefore further reduce the motion of land-terminating margins of the GIS. Our findings suggest that these sectors of the ice sheet are more resilient to the dynamic impacts of enhanced meltwater production than previously thought.
冰流向格陵兰冰盖（GIS）的陆地终止边缘的变化很大，这是对冰盖底部表面融水输入波动的响应。这种输入会润滑冰床界面，暂时加速冰的流动。由于形成了一个有效的排水系统，使水从冰床底部基底水压高的区域排出，导致夏季融化更多，冰的运动速度更快，但随后的冬季运动速度较慢。然而，水动力耦合对冰在数十年时间尺度上的运动的影响仍然受到很大限制。在这里，我们表明，在海平面以上 1100 米处延伸到 8000 平方公里的 GIS 西部陆地终止区，2007-14 年的年冰运动速度比 1985-94 年慢了 12%，尽管表面融水产量增加了 50%。我们的发现表明，在这三十年中，消融区这一部分的水动力耦合导致冰运动净减速（而不是如前所述的加速）。预计气候变暖导致的融水产量增加，可能会进一步降低 GIS 陆地终止边缘的运动。我们的发现表明，与之前的想法相比，这些冰原的区域对增强的融水产量的动态影响更具弹性。
