Longitudinal surface structures (flowstripes) on Antarctic glaciers
Longitudinal surface structures (flowstripes) on Antarctic glaciers
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DOI：
10.5194/tc-6-383-2012
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发表时间：
2011-11
期刊：
影响因子：
--
通讯作者：
N. Glasser;G. Gudmundsson
中科院分区：
文献类型：
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作者：
N. Glasser;G. Gudmundsson
纵向表面结构（“流动条纹”）在许多冰川上很常见，但对其起源和意义知之甚少。在本文中，我们提出的意见，这些纵向结构的发展，从四个不同的南极冰川系统的兰伯特冰川/Amery冰架区，泰勒和Ferrar冰川在罗斯海部门，起重机和Jorum冰川（冰架支流冰川）在南极半岛，和一个支流的恢复冰川冰流在Filchner冰架区的起始区。光学卫星图像的测绘表明，纵向表面结构主要在两种情况下形成：（1）冰川流动单元内相对较宽的流动条纹;（2）在冰原岛峰周围或冰川汇合区存在汇流的情况下相对较窄的流动条纹。我们的观察结果表明，汇合功能更窄，更尖锐，更明确的功能。它们的特征是冰面上的线性槽或凹陷，比前一种类型更常见。冰川流动单元内的纵向表面结构以前被解释为局部床扰动的表面表达，但缺乏对冰川汇合处形成的表面结构的普遍解释。在这里，我们建议，这些功能是在冰川汇合处的冰加速和伸展流区形成的。我们提供了一个示意性的模型，纵向表面结构的发展的基础上伸展流，可以解释他们的脊和槽的形态，以及他们的冰的持久性。
Longitudinal surface structures ("flowstripes") are common on many glaciers but their origin and significance are poorly understood. In this paper we present observations of the development of these longitudinal structures from four different Antarctic glacier systems; the Lambert Glacier/Amery Ice Shelf area, the Taylor and Ferrar Glaciers in the Ross Sea sector, Crane and Jorum Glaciers (ice-shelf tributary glaciers) on the Antarctic Peninsula, and the onset zone of a tributary to the Recovery Glacier Ice Stream in the Filchner Ice Shelf area. Mapping from optical satellite images demonstrates that longitudinal surface structures develop in two main situations: (1) as relatively wide flow stripes within glacier flow units and (2) as relatively narrow flow stripes where there is convergent flow around nunataks or at glacier confluence zones. Our observations indicate that the confluence features are narrower, sharper, and more clearly defined features. They are characterised by linear troughs or depressions on the ice surface and are much more common than the former type. Longitudinal surface structures within glacier flow units have previously been explained as the surface expression of localised bed perturbations but a universal explanation for those forming at glacier confluences is lacking. Here we propose that these features are formed at zones of ice acceleration and extensional flow at glacier confluences. We provide a schematic model for the development of longitudinal surface structures based on extensional flow that can explain their ridge and trough morphology as well as their down-ice persistence.