Ribbed bedforms on palaeo-ice stream beds resemble regular patterns of basal shear stress (‘traction ribs’) inferred from modern ice streams
Ribbed bedforms on palaeo-ice stream beds resemble regular patterns of basal shear stress (‘traction ribs’) inferred from modern ice streams
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古冰河床上的肋状河床形态类似于从现代冰流推断出的基础剪切应力的规则模式（“牵引肋”）
DOI：
10.1017/jog.2016.63
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发表时间：
2016
影响因子：
3.4
通讯作者：
T. Creyts
中科院分区：
文献类型：
--
作者：
C. Stokes;M. Margold;T. Creyts
快速流动的冰流是冰盖失去质量的重要机制，许多工作都集中在阐明增加或减少冰盖速度的过程上。最近使用标准逆方法的研究已经推断出在南极洲和格陵兰岛的一些冰流之下的高基础切应力(粘性斑点)的规律模式，这些高剪应力被称为“牵引肋”。它们出现在古冰盖床上观察到的较小的肋状冰雹和大得多的巨型肋骨之间，但尚不清楚它们在床上是否有地形表达。在这里，我们报道了在加拿大西部古冰川河床上发现的DEM中的肋状床形，它与牵引肋骨的图案和尺寸都很相似。它们的鉴定表明，牵引肋的地形表达可能位于肋状冰雹和更大的巨型肋间，并与之部分重叠。这些中等大小的床面支持肋状床面连续体的概念。它们的形成仍然是猜测，但我们对古冰流的观察，加上来自现代冰块的观察，表明它们与冰川和冰川耦合流动中发生的波状不稳定有关，并受到冰川下融水排放的调制。它们的形式和模式也可能涉及冰下沉积物的冰川构造作用。
Rapidly-flowing ice streams are an important mechanism through which ice sheets lose mass, and much work has been focussed on elucidating the processes that increase or decrease their velocity. Recent work using standard inverse methods has inferred previously-unrecognised regular patterns of high basal shear stress (‘sticky spots’ >200 kPa) beneath a number of ice streams in Antarctica and Greenland, termed ‘traction ribs’. They appear at a scale intermediate between smaller ribbed moraines and much larger mega-ribs observed on palaeo-ice sheet beds, but it is unclear whether they have a topographic expression at the bed. Here, we report observations of rib-like bedforms from DEMs along palaeo-ice stream beds in western Canada that resemble both the pattern and dimensions of traction ribs. Their identification suggests that traction ribs may have a topographic expression that lies between, and partly overlaps with, ribbed moraines and much larger mega-ribs. These intermediate-sized bedforms support the notion of a ribbed bedform continuum. Their formation remains conjectural, but our observations from palaeo-ice streams, coupled with those from modern ice masses, suggest they are related to wave-like instabilities occurring in the coupled flow of ice and till and modulated by subglacial meltwater drainage. Their form and pattern may also involve glaciotectonism of subglacial sediments.
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影响因子：
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