Retreat of calving glaciers worldwide has contributed substantially to sea-level rise in recent decades. Mass loss by calving contributes significantly to the uncertainty of sea-level rise projections. At Bowdoin Glacier, Northwest Greenland, most calving occurs by a few large events resulting from kilometre-scale fractures forming parallel to the calving front. High-resolution terrestrial radar interferometry data of such an event reveal that crevasse opening is fastest at low tide and accelerates during the final 36 h before calving. Using the ice flow model Elmer/Ice, we identify the crevasse water level as a key driver of modelled opening rates. Sea water-level variations in the range of local tidal amplitude (1 m) can reproduce observed opening rate fluctuations, provided crevasse water level is at least 4 m above the low-tide sea level. The accelerated opening rates within the final 36 h before calving can be modelled by additional meltwater input into the crevasse, enhanced ice cliff undercutting by submarine melt, ice damage increase due to tidal cyclic fatigue, crevasse deepening or a combination of these processes. Our results highlight the influence of surface meltwater and tides on crevasse opening leading to major calving events at grounded tidewater glaciers such as Bowdoin.

中文翻译：

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在格陵兰西北部鲍登冰川发生重大产犊事件之前，潮汐调节了裂缝的开口

近几十年来，全球冰川消融对海平面上升做出了重大贡献。产犊造成的质量损失极大地增加了海平面上升预测的不确定性。在格陵兰岛西北部的鲍登冰川，大多数崩解是由与崩解前沿平行形成的千米级裂缝造成的一些大型事件发生的。此类事件的高分辨率地面雷达干涉测量数据表明，裂缝开口在退潮时最快，并在产犊前的最后 36 小时内加速。使用冰流模型 Elmer/Ice，我们将裂缝水位确定为模拟开口率的关键驱动因素。如果裂缝水位至少高于低潮海平面 4 m，则局部潮幅（1 m）范围内的海水水位变化可以重现观察到的开口率波动。产犊前最后 36 小时内的加速开放率可以通过额外的融水输入裂缝、海底融化增强的冰崖底切、潮汐循环疲劳导致的冰损伤增加、裂缝加深或这些过程的组合来模拟。我们的研究结果强调了地表融水和潮汐对裂缝开口的影响，导致鲍登等接地潮水冰川发生重大崩塌事件。