Surface‐derived meltwater can access the bed of the Greenland ice sheet, causing seasonal velocity variations. The magnitude, timing, and net impact on annual average ice flow of these seasonal perturbations depend on the hydraulic efficiency of the subglacial drainage system. We examine the relationships between drainage system efficiency and ice velocity, at three contrasting tidewater glaciers in southwest Greenland during 2014–2019, using high‐resolution remotely sensed ice velocities, modeled surface melting, subglacial discharge at the terminus, and results from buoyant plume modeling. All glaciers underwent a seasonal speed‐up, which usually coincided with surface melt onset, and subsequent slow‐down, which usually followed inferred subglacial channelization. The amplitude and timing of these speed variations differed between glaciers, with the speed‐up being larger and more prolonged at our fastest study glacier. At all glaciers, however, the seasonal variations in ice flow are consistent with inferred changes in hydraulic efficiency of the subglacial drainage system and qualitatively indicative of a flow regime in which annually averaged ice velocity is relatively insensitive to interannual variations in meltwater supply—so‐called “ice flow self‐regulation.” These findings suggest that subglacial channel formation may exert a strong control on seasonal ice flow variations, even at fast‐flowing tidewater glaciers.

中文翻译：

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冰川下排水演化调节了西南格陵兰岛三个潮水冰川的季节性冰流量变化

来自地表的融化水可以进入格陵兰冰原的床层，导致季节性速度变化。这些季节性扰动对年平均冰流量的大小，时间和净影响取决于冰川下排水系统的水力效率。我们使用高分辨率的遥感冰速，模拟的表面融化，终点处的冰川下流量以及浮羽羽化模型的结果，研究了格陵兰岛西南部2014-2019年之间三个相对的潮水冰川的排水系统效率与冰速之间的关系。 。所有冰川都经历了季节性加速，这通常与表面融化的发生相吻合，随后又出现了减速，这通常归因于冰川下的通道化。这些速度变化的幅度和时间在冰川之间是不同的，在我们最快的研究冰川上，加速更大，更长。然而，在所有冰川，冰流量的季节性变化与推断的冰川下排水系统水力效率的变化是一致的，并且定性地表明了一种流动方式，其中年平均冰速对融水供应的年际变化相对不敏感，因此称为“冰流自我调节”。这些发现表明，即使在快速流动的潮水冰川上，冰河下通道的形成也可能对季节性冰流量的变化施加强有力的控制。冰流量的季节性变化与推断的冰川下排水系统的水力效率变化相一致，并定性地表明了一种流动方式，其中年平均冰速对融水供应量的年际变化相对不敏感，即所谓的“冰流自规。” 这些发现表明，即使在快速流动的潮水冰川上，冰河下通道的形成也可能对季节性冰流量的变化施加强有力的控制。冰流量的季节性变化与推断的冰川下排水系统的水力效率变化相一致，并定性地表明了一种流动方式，其中年平均冰速对融水供应量的年际变化相对不敏感，即所谓的“冰流自规。” 这些发现表明，即使在快速流动的潮水冰川上，冰河下通道的形成也可能对季节性冰流量的变化施加强有力的控制。