Ice stream motion facilitated by a shallow-deforming and accreting bed.
Ice stream motion facilitated by a shallow-deforming and accreting bed.
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DOI：
10.1038/ncomms10723
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发表时间：
2016-02-22
影响因子：
16.6
通讯作者：
Szuman I
中科院分区：
文献类型：
--
作者：
Spagnolo M;Phillips E;Piotrowski JA;Rea BR;Clark CD;Stokes CR;Carr SJ;Ely JC;Ribolini A;Wysota W;Szuman I
冰流使大部分冰盖流失，在控制冰盖对大气和海洋强迫的反应方面发挥着根本作用，并对海平面变化产生影响。产生冰流的机制仍然难以捉摸。假设存在基底滑动和/或床的变形，但冰河床在很大程度上是不可接近的。在这里，我们提出了一个全面的，多尺度的研究巨型冰川线（MSGLs）的内部结构形成于古冰流的床。在宏观和微观尺度上进行了分析，使用了多种技术，包括x射线断层扫描、薄片和探地雷达（GPR）采集。结果显示在地层学、运动学、粒度学和岩石学上均有均匀性。物理地质性质的一致性表现为连续增生、浅变形、床层和不变的基础条件。这意味着MSGL形成期间软沉积物床上的冰流基底运动是由塑性变形调节的，连续的泥沙供应和低效的排水系统促进了冰流的运动。冰流是冰盖动力学的基础，但控制其流动的机制仍然难以捉摸。在这里，作者进行了大尺度冰川线的宏观和微观分析，这表明在冰流流动期间，一个持续增加的浅变形床。
Ice streams drain large portions of ice sheets and play a fundamental role in governing their response to atmospheric and oceanic forcing, with implications for sea-level change. The mechanisms that generate ice stream flow remain elusive. Basal sliding and/or bed deformation have been hypothesized, but ice stream beds are largely inaccessible. Here we present a comprehensive, multi-scale study of the internal structure of mega-scale glacial lineations (MSGLs) formed at the bed of a palaeo ice stream. Analyses were undertaken at macro- and microscales, using multiple techniques including X-ray tomography, thin sections and ground penetrating radar (GPR) acquisitions. Results reveal homogeneity in stratigraphy, kinematics, granulometry and petrography. The consistency of the physical and geological properties demonstrates a continuously accreting, shallow-deforming, bed and invariant basal conditions. This implies that ice stream basal motion on soft sediment beds during MSGL formation is accommodated by plastic deformation, facilitated by continuous sediment supply and an inefficient drainage system. Ice streams are fundamental to ice sheet dynamics, but the mechanisms controlling their flow remain elusive. Here, the authors perform macro- and microscale analyses of mega-scale glacial lineations, which indicate a continuously accreting, shallow-deforming bed during ice stream flow.