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The hydrology of glacier-bed overdeepenings: Sediment transport mechanics, drainage system morphology, and geomorphological implications
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2021-06-03 , DOI: 10.1002/esp.5173 Darrel A. Swift 1 , Guy D. Tallentire 1, 2 , Daniel Farinotti 3, 4 , Simon J. Cook 5, 6 , William J. Higson 1 , Robert G. Bryant 1
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2021-06-03 , DOI: 10.1002/esp.5173 Darrel A. Swift 1 , Guy D. Tallentire 1, 2 , Daniel Farinotti 3, 4 , Simon J. Cook 5, 6 , William J. Higson 1 , Robert G. Bryant 1
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Evacuation of basal sediment by subglacial drainage is an important mediator of rates of glacial erosion and glacier flow. Glacial erosion patterns can produce closed basins (i.e., overdeepenings) in glacier beds, thereby introducing adverse bed gradients that are hypothesized to reduce drainage system efficiency and thus favour basal sediment accumulation. To establish how the presence of a terminal overdeepening might mediate seasonal drainage system evolution and glacial sediment export, we measured suspended sediment transport from Findelengletscher, Switzerland during late August and early September 2016. Analyses of these data demonstrate poor hydraulic efficiency of drainage pathways in the terminus region but high sediment availability. Specifically, the rate of increase of sediment concentration with discharge was found to be significantly lower than that anticipated if channelized flow paths were present. Sediment availability to these flow paths was also higher than would be anticipated for discrete bedrock-floored subglacial channels. Our findings indicate that subglacial drainage in the terminal region of Findelengletscher is dominated by distributed flow where entrainment capacity increases only marginally with discharge, but flow has extensive access to an abundant sediment store. This high availability maintains sediment connectivity between the glacial and proglacial realm and means daily sediment yield is unusually high relative to yields exhibited by similar Alpine glaciers. We present a conceptual model illustrating the potential influence of ice-bed morphology on subglacial drainage evolution and sediment evacuation mechanics, patterns and yields, and recommend that bed morphology should be an explicit consideration when monitoring and evaluating glaciated basin sediment export rates.
中文翻译：
冰川床过深的水文学：沉积物输送力学、排水系统形态和地貌意义
通过冰下排水疏散基底沉积物是冰川侵蚀和冰川流动速率的重要调节因素。冰川侵蚀模式可以在冰川床中产生封闭的盆地（即过度加深），从而引入不利的床梯度，假设会降低排水系统效率，从而有利于基底沉积物的积累。为了确定终端过度深化的存在如何调节季节性排水系统演变和冰川沉积物出口，我们在 2016 年 8 月下旬和 9 月初测量了来自瑞士芬德伦莱彻的悬浮沉积物输送。对这些数据的分析表明，该地区排水路径的水力效率较差。终点区，但沉积物可用性高。具体来说，如果存在渠道化的流动路径，则发现随着排放的沉积物浓度的增加速率显着低于预期。这些流动路径的沉积物可用性也高于离散基岩地层冰下通道的预期。我们的研究结果表明，Findelengletscher 末端区域的冰下排水以分布式流为主，其中夹带能力仅随排放而略微增加，但流可广泛进入丰富的沉积物库。这种高可用性保持了冰川和前冰界之间的沉积物连通性，这意味着相对于类似的高山冰川所表现出的产量，每日沉积物产量异常高。
更新日期：2021-06-03
中文翻译：
冰川床过深的水文学：沉积物输送力学、排水系统形态和地貌意义
通过冰下排水疏散基底沉积物是冰川侵蚀和冰川流动速率的重要调节因素。冰川侵蚀模式可以在冰川床中产生封闭的盆地（即过度加深），从而引入不利的床梯度，假设会降低排水系统效率，从而有利于基底沉积物的积累。为了确定终端过度深化的存在如何调节季节性排水系统演变和冰川沉积物出口，我们在 2016 年 8 月下旬和 9 月初测量了来自瑞士芬德伦莱彻的悬浮沉积物输送。对这些数据的分析表明，该地区排水路径的水力效率较差。终点区，但沉积物可用性高。具体来说，如果存在渠道化的流动路径，则发现随着排放的沉积物浓度的增加速率显着低于预期。这些流动路径的沉积物可用性也高于离散基岩地层冰下通道的预期。我们的研究结果表明，Findelengletscher 末端区域的冰下排水以分布式流为主，其中夹带能力仅随排放而略微增加，但流可广泛进入丰富的沉积物库。这种高可用性保持了冰川和前冰界之间的沉积物连通性，这意味着相对于类似的高山冰川所表现出的产量，每日沉积物产量异常高。
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