Van Wyk de Vries Maximillian, Lea James M, Ashmore David W
Department of Geography and Planning, University of Liverpool, Liverpool L69 7ZT, UK.
School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK.
J Glaciol. 2023 Oct;69(277):1125-1137. doi: 10.1017/jog.2023.3. Epub 2023 Mar 29.
Mass loss from iceberg calving at marine-terminating glaciers is one of the largest and most poorly constrained contributors to sea-level rise. However, our understanding of the processes controlling ice fracturing and crevasse evolution is incomplete. Here, we use Gabor filter banks to automatically map crevasse density and orientation through time on a ~150 km terminus region of Narsap Sermia, an outlet glacier of the southwest Greenland ice sheet. We find that Narsap Sermia is dominated by transverse (flow-perpendicular) crevasses near the ice front and longitudinal (flow-aligned) crevasses across its central region. Measured crevasse orientation varies on sub-annual timescales by more than 45 in response to seasonal velocity changes, and also on multi-annual timescales in response to broader dynamic changes and glacier retreat. Our results show a gradual up-glacier propagation of the zone of flow-transverse crevassing coincident with frontal retreat and acceleration occurring in 2020/21, in addition to sub-annual crevasse changes primarily in transition zones between longitudinal to transverse crevasse orientation. This provides new insight into the dynamics of crevassing at large marine-terminating glaciers and a potential approach for the rapid identification of glacier dynamic change from a single pair of satellite images.
海洋末端冰川的冰山崩解造成的质量损失是海平面上升的最大且最难以精确测定的因素之一。然而，我们对控制冰破裂和裂隙演化过程的理解并不完整。在此，我们使用伽柏滤波器组，对格陵兰冰原西南部的一条外流冰川纳尔萨普·塞尔米亚约150公里长的末端区域随时间变化的裂隙密度和方向进行自动测绘。我们发现，纳尔萨普·塞尔米亚在冰前沿附近以横向（垂直于流动方向）裂隙为主，而在其中心区域则以纵向（与流动方向一致）裂隙为主。实测的裂隙方向在亚年度时间尺度上会因季节性速度变化而改变超过45度，在多年时间尺度上也会因更广泛的动态变化和冰川退缩而改变。我们的结果表明，与2020/21年发生的前沿退缩和加速同时出现的是，流动横向裂隙带逐渐向上游扩展，此外，裂隙的亚年度变化主要发生在纵向裂隙方向与横向裂隙方向的过渡区域。这为大型海洋末端冰川的裂隙形成动态提供了新的见解，并为从单对卫星图像快速识别冰川动态变化提供了一种潜在方法。
