Englacial phase changes and intergranular flow above subglacial lakes
Englacial phase changes and intergranular flow above subglacial lakes
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冰期相变和冰下湖泊上方的粒间流
作者：
A. Rempel
摘要冰川中充满了液体脉，它们排列在冰粒之间的三重连接点上，充当着物质运输的管道。水和冰之间的密度差产生了一个水力梯度，驱使液体流向冰川床。我们调查如何在这种运输率的变化是在较低的地区的冰川，漂浮在冰下水库。当温度向冰川床方向上升时，相关的渗透性增加导致更快的流体输送;内部融化提供了不断变化的流动。水力梯度的降低是由于表面能量的影响，并导致底部附近的输运速率降低;因此，多晶冰内发生冻结。对于热通量、可溶性杂质含量和粒度的代表性值，向下通量的峰值大约在冰川床上方几十厘米处的1 - 100mma-1。在这一水平之下，表面能的作用控制着流体的输送，并使流动方向相反，将液体向上拉入多晶冰中，这样流动就不会将冰川物质引入下面的水库。
Abstract Glaciers are permeated by liquid veins that line the triple junctions between ice grains and act as conduits for material transport. The density difference between water and ice produces a hydraulic gradient that drives liquid flow down towards the glacier bed. We investigate how variations in this transport rate are manifest in the lower regions of a glacier that floats on a subglacial reservoir. When the temperature rises towards the glacier bed, the associated permeability increase leads to more rapid fluid transport; internal melting supplies the changing flow. A reduction in hydraulic gradient results from surface energy effects, and causes a decreasing transport rate near the base; hence, freezing occurs within the polycrystalline ice. For representative values of the heat flux, soluble impurity loading and grain-size, the downward flux peaks at approximately 1–100mma–1 several tens of centimeters above the glacier bed. Beneath this level, the effects of surface energy control the fluid transport and cause the flow to reverse directions, pulling liquid upwards into the polycrystalline ice so that the flow does not introduce glacial material into the underlying reservoir.