Recent seismic measurements from upper Thwaites Glacier indicate that the bed-type variability is closely related to the along-flow basal topography. In high-relief subglacial highlands, stoss sides of topographic highs have a relatively higher acoustic impedance (‘hard’ bed) with lower acoustic impedance (‘soft’ till) on lee sides. This pattern is similar to observations of many deglaciated terrains. Subglacial hydraulic-potential gradient and its divergence show a tendency for water to diverge over the stoss sides and converge into the lee sides. Convergence favors a thicker or more widespread water system, which can more efficiently decouple ice from the underlying till. Under such circumstances, till deformation does occur but, fluxes are relatively small. Till carried from the lee sides onto stoss sides of downstream bumps should couple to the ice more efficiently, increasing the ability for transport by till deformation. In turn, this suggests that steady-state till transport can be achieved if the stoss-side till layer is thin or discontinuous. In addition, the large basal shear stress generated in the highlands seems too high for a bed lubricated by a continuous although thin deforming till, suggesting till discontinuity, which would allow debris-laden ice to erode bedrock on stoss sides, supplying additional till for transport.

中文翻译：

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西南极洲 Thwaites 冰川下的床型变化和直到（不）连续性

最近从 Thwaites Glacier 上部进行的地震测量表明，床型变化与沿流基底地形密切相关。在高地势冰下高地，地形高地的 stoss 面具有相对较高的声阻抗（“硬”床），而背风面的声阻抗较低（“软”床）。这种模式类似于对许多冰川消融地形的观察。冰下水位势梯度及其发散表明水有在stoss两侧发散并会聚到背风面的趋势。趋同有利于更厚或更广泛的水系统，这可以更有效地将冰与下面的冰碛分开。在这种情况下，直到发生变形，但通量相对较小。从背风侧携带到下游隆起的 stoss 侧的冰块应该更有效地连接到冰上，通过冰块变形增加运输能力。反过来，这表明如果 stoss 侧直到层薄或不连续，则可以实现稳态直到传输。此外，高地产生的大的基础剪切应力对于由连续但薄的变形直到润滑的床来说似乎太高了，这表明直到不连续，这将使载有碎屑的冰侵蚀岸边的基岩，为运输提供额外的直到.