1] Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853, USA [2] Department of Geological Sciences, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Polar Geospatial Center, University of Minnesota, Saint Paul, Minnesota 55108, USA.
Nature. 2015 Feb 12;518(7538):223-7. doi: 10.1038/nature14116. Epub 2015 Jan 21.
In a warming climate, surface meltwater production on large ice sheets is expected to increase. If this water is delivered to the ice sheet base it may have important consequences for ice dynamics. For example, basal water distributed in a diffuse network can decrease basal friction and accelerate ice flow, whereas channelized basal water can move quickly to the ice margin, where it can alter fjord circulation and submarine melt rates. Less certain is whether surface meltwater can be trapped and stored in subglacial lakes beneath large ice sheets. Here we show that a subglacial lake in Greenland drained quickly, as seen in the collapse of the ice surface, and then refilled from surface meltwater input. We use digital elevation models from stereo satellite imagery and airborne measurements to resolve elevation changes during the evolution of the surface and basal hydrologic systems at the Flade Isblink ice cap in northeast Greenland. During the autumn of 2011, a collapse basin about 70 metres deep and about 0.4 cubic kilometres in volume formed near the southern summit of the ice cap as a subglacial lake drained into a nearby fjord. Over the next two years, rapid uplift of the floor of the basin (which is approximately 8.4 square kilometres in area) occurred as surface meltwater flowed into crevasses around the basin margin and refilled the subglacial lake. Our observations show that surface meltwater can be trapped and stored at the bed of an ice sheet. Sensible and latent heat released by this trapped meltwater could soften nearby colder basal ice and alter downstream ice dynamics. Heat transport associated with meltwater trapped in subglacial lakes should be considered when predicting how ice sheet behaviour will change in a warming climate.
在气候变暖的情况下，预计大型冰原的表面融水产量将会增加。如果这些水被输送到冰原底部，可能会对冰动力学产生重要影响。例如，分布在弥散网络中的基底水可以降低基底摩擦力并加速冰流，而通道化的基底水可以迅速移动到冰缘，从而改变峡湾的循环和海底的融化速度。不太确定的是，表面融水是否可以被困在大型冰原下的冰下湖中并储存起来。在这里，我们表明，格陵兰的一个冰下湖迅速排干，从冰面的坍塌中可以看出，然后从表面融水的输入中重新填满。我们利用立体卫星图像和航空测量的数字高程模型，来解决格陵兰东北部 Flade Isblink 冰帽表面和基底水文系统演化过程中的高程变化。在 2011 年秋季，一个约 70 米深、体积约 0.4 立方公里的崩塌盆地在冰帽的南部山顶附近形成，一个冰下湖排入附近的峡湾。在接下来的两年里，随着表面融水流进盆地边缘的裂缝并重新填满冰下湖，盆地底部（面积约 8.4 平方公里）迅速隆起。我们的观测表明，表面融水可以被困在冰原的底部并储存起来。这些被困融水释放的显热和潜热可能会软化附近较冷的基底冰，并改变下游的冰动力学。在预测冰盖行为在气候变暖的情况下将如何变化时，应该考虑与冰下湖中的被困融水相关的热传输。
