Bedforms of Thwaites Glacier, West Antarctica: Character and Origin
Bedforms of Thwaites Glacier, West Antarctica: Character and Origin
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DOI：
10.1029/2021jf006339
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发表时间：
2021-12-01
影响因子：
3.9
通讯作者：
Stevens, N.
中科院分区：
文献类型：
--
作者：
Alley, R. B.;Holschuh, N.;Stevens, N.
地球物理资料和简单模型表明，西南极斯韦茨冰川的底形记录并影响着冰流。斯韦茨冰川流经西南极裂谷系统的构造结构，其基岩高地和沉积盆地。对冰川床的条带雷达和地震勘测显示，软沉积物槽高100米或更高，从基岩高处向冰川下游延伸15公里或更长，穿过盆地。凹槽终止于下一个地形高点的突出的硬层护城河。我们使用简单的模型来表明，冰流对地形增加之间的压力，直到沿沿着床的距离，与地形的规模。在这个高压基底区，冰接触水将被排除在外，从而通过增加冰碛耦合和冰碛通量来增加基底阻力，去除冰碛以允许基岩侵蚀，从而形成护城河。然后，穿过高地的冰碛物将沉积在背风面的位置，形成随着时间的推移而向冰川下移动的床形，并通过与地形上的冰川井的冰碛变形通量相匹配的反馈，在顶部保持柔软。这里调查的思韦茨部分的底形是突出的，因为冰流在这种地质背景下持续了很长时间，而不是因为冰流是异常的。随着时间的推移，冰碛和润滑水被重新分配，护城河被侵蚀，底形变大，底形的发展可能导致冰流的演变。简明语言摘要南极洲西部的思韦茨冰川非常有趣，因为持续的退缩可能导致未来更快的变化，可能会显著增加海平面上升。因此，广泛的研究集中在对冰川的广泛了解上。这里讨论的地球物理调查表明，冰川床已经被流动的冰雕刻，侵蚀大的“护城河”上冰川和基岩障碍物的侧面，并沉积长尾巴的软沉积物下冰川的这些障碍物。我们使用简单的模型来表明，这些功能随着时间的推移形成，因为冰，基岩，冰下水和沉积物之间的相互作用，冰川的行为必须改变这些功能的发展。这些知识并不直接影响对未来海平面上升潜力的估计，但确实指导了进一步的研究，以改善这些估计。这一知识也可能有助于理解前冰盖在广泛地区留下的冰川雕刻景观的形成。
Bedforms of Thwaites Glacier, West Antarctica both record and affect ice flow, as shown by geophysical data and simple models. Thwaites Glacier flows across the tectonic fabric of the West Antarctic rift system with its bedrock highs and sedimentary basins. Swath radar and seismic surveys of the glacier bed have revealed soft-sediment flutes 100 m or more high extending 15 km or more across basins downglacier from bedrock highs. Flutes end at prominent hard-bedded moats on stoss sides of the next topographic highs. We use simple models to show that ice flow against topography increases pressure between ice and till upglacier along the bed over a distance that scales with the topography. In this basal zone of high pressure, ice-contact water would be excluded, thus increasing basal drag by increasing ice-till coupling and till flux, removing till to allow bedrock erosion that creates moats. Till carried across highlands would then be deposited in lee-side positions forming bedforms that prograde downglacier over time, and that remain soft on top through feedbacks that match till-deformational fluxes from well upglacier of the topography. The bedforms of the part of Thwaites surveyed here are prominent because ice flow has persisted over a long time on this geological setting, not because ice flow is anomalous. Bedform development likely has caused evolution of ice flow over time as till and lubricating water were redistributed, moats were eroded and bedforms grew.Plain Language Summary Thwaites Glacier, West Antarctica, is of great interest because ongoing retreat could lead to faster future changes that could notably increase sea-level rise. Wide-ranging studies are thus focused on gaining broad understanding of the glacier. Geophysical surveys discussed here show that the bed of the glacier has been sculpted by the flowing ice, eroding large "moats" upglacier and to the sides of bedrock obstacles, and depositing long tails of soft sediment downglacier of those obstacles. We use simple models to show that these features formed over time because of the interactions among ice, bedrock, and subglacial water and sediment, and that the behavior of the glacier must have changed as these features developed. This knowledge does not directly affect estimates of the potential for future sea-level rise, but does guide further studies to improve those estimates. This knowledge also may help understand the formation of glacially sculpted landscapes left in widespread regions by former ice sheets.