The influence of a model subglacial lake on ice dynamics and internal layering
The influence of a model subglacial lake on ice dynamics and internal layering
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冰下湖模型对冰动力学和内部分层的影响
DOI：
10.5194/tc-10-751-2016
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
K. Andreassen
中科院分区：
文献类型：
--
作者：
E. Gudlaugsson;A. Humbert;T. Kleiner;J. Kohler;K. Andreassen
抽象的。当冰流过冰下湖时，床阻力的下降导致冰速度增加以及等时线和冷冰的下降。当冰面适应底部阻力的缺乏时，它会变平。速度的快速转变会引起冰粘度的变化并释放变形能，从而局部升高温度。最近对南极冰下湖泊的研究表明，许多湖泊经历了非常快速且可能是间歇性的排水，在此期间，随着水的流出，湖泊面积迅速缩小。出现的问题是这会对冰内层产生什么影响，以及是否可以从下游的等时线结构推断出过去的排水事件。在这里，我们研究冰下湖对冰动力学的影响，以及这种短时间尺度的排水对冰内层的影响。为此，我们使用完整的斯托克斯多温冰流模型。焓梯度法用于解释冰内温度和水含量的变化。我们发现，湖外缓慢移动的冰与湖上完全滑动之间的快速过渡可以释放大量的变形能，有可能在过渡区的深处形成温带层。此外，我们还对冰下湖泊边缘常见的特征性表面特征提供了解释，即在很少滑动到完全滑动之间的过渡区域中的丘状表面凹陷。我们还得出结论，与平均冰柱速度相比，冰下湖泊和湿滑斑块水平范围的快速变化可以在等时线结构的深处产生行波，该行波随着冰的平流向下游传播，从而表明用冰穿透雷达探测过去的排水事件的可能性。
Abstract. As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a draw down of isochrones and cold ice. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in ice viscosity and releases deformation energy that can raise the temperature locally. Recent studies of Antarctic subglacial lakes indicate that many lakes experience very fast and possibly episodic drainage, during which the lake size is rapidly reduced as water flows out. Questions that arise are what effect this would have on internal layers within the ice and whether such past drainage events could be inferred from isochrone structures downstream. Here, we study the effect of a subglacial lake on ice dynamics as well as the influence that such short timescale drainage would have on the internal layers of the ice. To this end, we use a full Stokes, polythermal ice flow model. An enthalpy-gradient method is used to account for the evolution of temperature and water content within the ice. We find that a rapid transition between slow-moving ice outside the lake, and full sliding over the lake, can release considerable amounts of deformational energy, with the potential to form a temperate layer at depth in the transition zone. In addition, we provide an explanation for a characteristic surface feature commonly seen at the edges of subglacial lakes, a hummocky surface depression in the transition zone between little to full sliding. We also conclude that rapid changes in the horizontal extent of subglacial lakes and slippery patches, compared to the average ice column velocity, can create a traveling wave at depth within the isochrone structure that transfers downstream with the advection of ice, thus indicating the possibility of detecting past drainage events with ice penetrating radar.
影响因子：
1.6
作者：
Andrew Wright;M. Siegert
通讯作者：
Andrew Wright;M. Siegert