Numerical Modeling Shows Increased Fracturing Due to Melt-Undercutting Prior to Major Calving at Bowdoin Glacier
Numerical Modeling Shows Increased Fracturing Due to Melt-Undercutting Prior to Major Calving at Bowdoin Glacier
复制标题
数值模型显示，鲍登冰川在发生重大崩解之前，由于熔体底切而导致断裂增加
作者：
E. V. van Dongen;J. Åström;G. Jouvet;J. Todd;D. Benn;M. Funk
对未来冰盖质量损失和海平面上升的预测依赖于冰盖模型中冰山崩解的参数化。海底融化引起的底切和崩解之间的相互关系仍然知之甚少，这使得潮水冰川对海平面上升的预测贡献不确定。在这里，我们将赫尔辛基离散元模型 (HiDEM) 获得的裂缝萌生详细 3D 模拟与格陵兰岛西北部鲍登冰川重大崩解事件之前的观测结果进行了比较。对崩解地点羽流表面的观察表明，局部熔体底切影响了主要崩解事件的规模。因此，对各种局部和分布式（前宽）底切几何形状进行了多次实验。尽管底切实验的数量受到计算要求的限制，但推测的底切几何形状之一非常详细地再现了导致观察到的主要崩解事件的裂缝。我们的模拟表明，底切导致在终点上游超过 100 m 处出现更宽的裂缝，远远超出直接底切区域。当在两个观察到的羽流处将中等分布的底切与局部放大的底切相结合时，局部底切之间的断裂起始也会增加。因此，我们的结果与之前的研究一致，表明海底融化（无论是在冰川上还是跨冰川）都存在“崩解放大器”效应。因此，模拟显示了海底融化引起的底切对冰山尺寸的潜在巨大影响。
Projections of future ice sheet mass loss and thus sea level rise rely on the parametrization of iceberg calving in ice sheet models. The interconnection between submarine melt-induced undercutting and calving is still poorly understood, which makes predicted contributions of tidewater glaciers to sea level rise uncertain. Here, we compare detailed 3-D simulations of fracture initiation obtained with the Helsinki Discrete Element Model (HiDEM) to observations, prior to a major calving event at Bowdoin Glacier, Northwest Greenland. Observations of a plume surfacing at the calving location suggest that local melt-undercutting influenced the size of the major calving event. Therefore, several experiments are conducted with various local and distributed (front-wide) undercut geometries. Although the number of undercut experiments is limited by computational requirements, one of the conjectured undercut geometries reproduces the crevasse leading to the observed major calving event in great detail. Our simulations show that undercutting leads to initiation of wider fractures more than 100 m upstream of the terminus, well-beyond the directly undercut region. When combining a moderate distributed undercut with local amplified undercuts at the two observed plumes, fracture initiation also increases in between the local undercuts. Thus, our results agree with previous studies suggesting the existence of a “calving amplifier” effect by submarine melt, both upglacier and across-glacier. Consequently, the simulations show the potentially large impact of submarine melt-induced undercutting on iceberg size.
格陵兰冰盖对未来海平面的贡献：ISMIP6 的多模型集成研究
DOI：
10.5194/tc-2019-319
发表时间：
2020
期刊：
--
影响因子：
--
作者：
Goelzer H
通讯作者：
Goelzer H