Basal crevasses in Larsen C Ice Shelf and implications for their global abundance
Basal crevasses in Larsen C Ice Shelf and implications for their global abundance
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DOI：
10.5194/tc-6-113-2012
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发表时间：
2012-01-01
期刊：
影响因子：
5.2
通讯作者：
Benn, D. I.
中科院分区：
文献类型：
--
作者：
Luckman, A.;Jansen, D.;Benn, D. I.
基裂缝从冰体底部向上延伸，在冰架上常见的条件下，可以穿透冰柱的一半以上。因此，它们可以局部地改变冰架和海洋之间的质量和能量交换，并通过改变冰架的力学性质，在冰架稳定性中发挥根本作用。虽然早期的研究表明，这些功能可能是丰富的南极冰架，其几何特性和空间分布很少得到关注。我们调查基础裂缝拉森C冰架使用现场雷达测量，遥感和数值模拟。我们证明了一组功能可见的MODIS图像中的表面表达的表面槽的形式的底裂缝，并发现，底裂缝可以产生的接地线的下游应力的结果。我们表明，线性弹性断裂力学模型是底部裂缝渗透高度的良好预测因素，其中应力主要是拉伸的，并且测量的表面槽深度并不总是反映该高度，可能是因为槽中积雪、海冰堆积。裂缝，或来自周围冰的应力桥接。我们的结论是，所有功能可见的MODIS图像的冰架和以前简单地标记为“裂缝”，他们不是全厚度裂缝，必须是基础裂缝槽，突出了许多冰架的基本结构特性，以前可能被忽视。
Basal crevasses extend upwards from the base of ice bodies and can penetrate more than halfway through the ice column under conditions found commonly on ice shelves. As a result, they may locally modify the exchange of mass and energy between ice shelf and ocean, and by altering the shelf's mechanical properties could play a fundamental role in ice shelf stability. Although early studies revealed that such features may be abundant on Antarctic ice shelves, their geometrical properties and spatial distribution has gained little attention. We investigate basal crevasses in Larsen C Ice Shelf using field radar survey, remote sensing and numerical modelling. We demonstrate that a group of features visible in MODIS imagery are the surface expressions of basal crevasses in the form of surface troughs, and find that basal crevasses can be generated as a result of stresses well downstream of the grounding line. We show that linear elastic fracture mechanics modelling is a good predictor of basal crevasse penetration height where stresses are predominantly tensile, and that measured surface trough depth does not always reflect this height, probably because of snow accumulation in the trough, marine ice accretion in the crevasse, or stress bridging from the surrounding ice. We conclude that all features visible in MODIS imagery of ice shelves and previously labelled simply as "crevasses", where they are not full thickness rifts, must be basal crevasse troughs, highlighting a fundamental structural property of many ice shelves that may have been previously overlooked.