Diurnal depth cycles of decimeter scale are observed in a supraglacial lake on the McMurdo Ice Shelf, Antarctica. We evaluate two possible causes: (1) tidal tilt of the ice shelf in response to the underlying ocean tide, and (2) meltwater input variation. We find the latter to be the most likely explanation of our observations. However, we do not rule out tidal tilt as a source of centimeter scale variations, and point to the possibility that other, larger supraglacial lake systems, particularly those on ice shelves that experience higher amplitude tidal tilts, such as in the Weddell Sea, may have depth cycles driven by ocean tide. The broader significance of diurnal cycles in meltwater depth is that, under circumstances where the ice shelf is thin, tidal-tilt amplitudes are high, and meltwater runoff rates are large, there may be associated flexure stresses that can contribute to ice-shelf fracture and destabilization. For the McMurdo Ice Shelf (~20–50 m thickness, ~ 1 m tidal amplitude and ~10 cm water-depth variations), these stresses amount to several 10's of kPa.

中文翻译：

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由融水输入和海洋潮汐倾斜驱动的冰架上的昼夜湖水循环

在南极洲麦克默多冰架上的冰上湖中观察到分米尺度的昼夜深度循环。我们评估了两个可能的原因：（1）冰架响应潜在海潮的潮汐倾斜，以及（2）融水输入变化。我们发现后者是我们观察到的最可能的解释。然而，我们不排除潮汐倾斜是厘米尺度变化的来源，并指出其他更大的冰上湖泊系统，特别是那些在经历更高幅度潮汐倾斜的冰架上的系统，例如威德尔海，可能有由海潮驱动的深度循环。融水深度日循环的更广泛意义在于，在冰架薄、潮汐倾斜幅度高、融水径流率大的情况下，可能存在可能导致冰架破裂和不稳定的相关弯曲应力。对于 McMurdo 冰架（约 20-50 m 厚度，约 1 m 潮汐幅度和约 10 cm 水深变化），这些应力相当于几十 kPa。