Vulnerability of Antarctica's ice shelves to meltwater-driven fracture
Vulnerability of Antarctica's ice shelves to meltwater-driven fracture
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DOI：
10.1038/s41586-020-2627-8
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发表时间：
2020-08-27
期刊：
影响因子：
64.8
通讯作者：
van Wessem, J. Melchior
中科院分区：
文献类型：
--
作者：
Lai, Ching-Yao;Kingslake, Jonathan;van Wessem, J. Melchior
大气变暖加剧了南极冰盖的表面融化，并促进了“水力压裂”（1-7），其中融水流入并扩大了裂缝，可能引发冰架崩塌（3-5,8-10）。支撑冰盖的冰架的崩塌加速了冰流和海平面的上升。然而，我们不知道如果被水淹没，南极洲冰架的支撑区域是否以及有多少容易受到水力压裂的影响。在这里，我们提供了两行证据，表明许多支撑区域是脆弱的。首先，我们训练了一个深度卷积神经网络（DCNN）来绘制所有南极冰架卫星图像中裂缝的表面表达。其次，我们基于线弹性断裂力学建立了裂缝稳定性图，以预测当前应力条件下基底和干表面裂缝的形成位置。尽管在卫星图像中检测裂缝存在局限性，但我们发现理论预测与dcnn绘制的裂缝之间存在密切的一致性。最后，我们使用线弹性断裂力学理论来预测如果充满水，地表裂缝会在哪里变得不稳定。如今，许多经常被融水淹没的地区对水力裂缝具有弹性——应力足够低，所有充满水的裂缝都是稳定的。相反，60% +/- 10%的冰架（按面积计算）既支撑上游的冰，如果被水淹没，就容易发生水力破裂。DCNN的地图证实了这些支撑区域存在裂缝。地表融化加剧（17）可能引发水力压裂，如果它导致水淹没我们确定的广泛的脆弱地区。这些地区是大气变暖可能对冰盖物质平衡影响最大的地区。通过对全大陆范围的数据和裂缝模型进行训练的神经网络，我们确定了在大气进一步变暖的情况下，南极洲的冰架可能容易发生水力压裂。
Atmospheric warming threatens to accelerate the retreat of the Antarctic Ice Sheet by increasing surface melting and facilitating 'hydrofracturing'(1-7), where meltwater flows into and enlarges fractures, potentially triggering ice-shelf collapse(3-5,8-10). The collapse of ice shelves that buttress(11-13)the ice sheet accelerates ice flow and sea-level rise(14-16). However, we do not know if and how much of the buttressing regions of Antarctica's ice shelves are vulnerable to hydrofracture if inundated with water. Here we provide two lines of evidence suggesting that many buttressing regions are vulnerable. First, we trained a deep convolutional neural network (DCNN) to map the surface expressions of fractures in satellite imagery across all Antarctic ice shelves. Second, we developed a stability diagram of fractures based on linear elastic fracture mechanics to predict where basal and dry surface fractures form under current stress conditions. We find close agreement between the theoretical prediction and the DCNN-mapped fractures, despite limitations associated with detecting fractures in satellite imagery. Finally, we used linear elastic fracture mechanics theory to predict where surface fractures would become unstable if filled with water. Many regions regularly inundated with meltwater today are resilient to hydrofracture-stresses are low enough that all water-filled fractures are stable. Conversely, 60 +/- 10 per cent of ice shelves (by area) both buttress upstream ice and are vulnerable to hydrofracture if inundated with water. The DCNN map confirms the presence of fractures in these buttressing regions. Increased surface melting(17)could trigger hydrofracturing if it leads to water inundating the widespread vulnerable regions we identify. These regions are where atmospheric warming may have the largest impact on ice-sheet mass balance.Using a neural network trained on continent-wide data and a fracture model, the ice shelves in Antarctica that may be prone to hydrofracturing under further atmospheric warming are identified.