Geophysical Studies of the Lateral Transition Zone of an Active Antarctic Ice Stream

地球主要冰盖的变形方式和速度取决于它们的地理和气候环境以及它们的内部动态的复杂相互作用。在西南极冰盖，众所周知，快速流动的冰流与大片停滞不前的冰交替，流动和非流动之间的过渡可能相当窄。在这些横向切变边缘，人们认为对冰流动力学的物理控制必须表现出显着的差异。这项研究将考察沿西南极Siple海岸的冰流和停滞的山脊之间的地球物理差异。将用电磁波和地震波探测冰，以推断冰的内部温度和晶体结构，以及旧(威斯康星州冰河时代)冰的比例，因为众所周知，冰的流动规律与温度成指数关系，冰晶在其六角形平面上的变形能力比在其他方向上要小得多，而且，旧冰可能比最近地质时代的冰更容易变形。雷达衍射图的测量和对微震记录的分析可以用来显示冰盖的底部是否冻结在下面的基岩上。

The manner and rate of deformation of the Earth's major ice sheets depend on a complex interplay of their geographical and climatic setting, as well as their internal dynamics. In the West Antarctic Ice Sheet, it is known that rapidly moving ice streams alternate with large areas of stagnant ice, and that the transition between streaming and non-streaming flow can be be quite narrow. In these lateral shear margins it is thought that the physical controls on ice stream dynamics must show significant differences. This study will examine the geophysical differences between an ice stream and a stagnant ridge along the Siple Coast in West Antarctica. The ice will be probed with electromagnetic and seismic waves to infer the internal temperature and the crystalline structure of the ice, as well as the proportion of old (Wisconsin Ice Age) ice, since it is known that ice flow laws depend exponentially on temperature, that ice crystals are much less resistant to deformation in the plane of their hexagonal faces than in other directions, and that old ice may deform much more readily than ice of more recent geological age. Measurement of radar diffraction patterns and the analysis of the records of micro- earthquakes can be used to show whether the base of the ice sheet is frozen to the underlying bedrock.