Numerical modeling of a gravity-driven instability of a cold hanging glacier: reanalysis of the 1895 break-off of Altelsgletscher, Switzerland
Numerical modeling of a gravity-driven instability of a cold hanging glacier: reanalysis of the 1895 break-off of Altelsgletscher, Switzerland
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DOI：
10.3189/002214311798043852
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发表时间：
2011-01-01
影响因子：
3.4
通讯作者：
Funk, Martin
中科院分区：
文献类型：
--
作者：
Faillettaz, Jerome;Sornette, Didier;Funk, Martin
瑞士的阿尔泰斯悬空冰川于1895年9月11日断裂。据估计，这次灾难性破裂的冰量为4 × 10(6) m(3)，是在阿尔卑斯山观测到的最大的冰瀑事件。然而，这种崩溃的原因尚不完全清楚。在先前研究的基础上，我们借助一个新的数值模型重新分析了这一断裂事件，该模型最初是由Faillettaz等人（2010）为重力驱动的不稳定性开发的。模拟表明，断裂事件只有在基岩上的基础摩擦在有限区域内减少时才有可能发生，这可能是由冰川内入渗水的储存引起的。此外，我们的模拟揭示了一个两步行为：(1)第一个静止阶段，没有明显的变化，其持续时间取决于基础摩擦的变化率；(2)在几天内基底运动迅速增加的活跃期。从模拟和现有观测结果的比较中得到的一般教训是，由于冰/床界面向温带状态逐渐变暖而导致的悬空冰川不稳定过程的可探测前兆（裂缝形成和速度增加）只会在断裂前几天出现。
The Altels hanging glacier in Switzerland broke off on 11 September 1895. The ice volume of this catastrophic rupture was estimated as 4 x 10(6) m(3), the largest icefall event ever observed in the Alps. However, the causes of this collapse are not entirely clear. Based on previous studies, we reanalyzed this break-off event, with the help of a new numerical model, initially developed by Faillettaz and others (2010) for gravity-driven instabilities. The simulations indicate that a break-off event is only possible when the basal friction at the bedrock is reduced in a restricted area, possibly induced by the storage of infiltrated water within the glacier. Further, our simulations reveal a two-step behavior: (1) a first quiescent phase, without visible changes, with a duration depending on the rate of change in basal friction; (2) an active phase with a rapid increase of basal motion over a few days. The general lesson obtained from the comparison between the simulations and available observations is that detectable precursors (crevasse formation and velocity increase) of the destabilization process of a hanging glacier, resulting from a progressive warming of the ice/bed interface towards a temperate regime, will appear only a few days prior to the break-off.