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[交流] Empirical constraints on ice cliff calving

Empirical constraints on ice cliff calving

冰崖崩解的约束限制

▲ 作者:Caroline Needell, Catherine C. Walker, and Jeremy N. Bassis

▲链接:

https://www.science.org/doi/10.1126/science.aee0658

▲摘要:

当地球冰盖边缘的崩解冰崖超过临界高度时,可能引发一种称为海洋冰崖不稳定性的失控退缩过程。然而,足够高的冰崖很少被观察到。为填补这一空白,研究者利用激光测高仪测量了地球冰盖边缘15330座冰崖的特征。

研究表明,冰崖高度与混杂岩厚度、水深和裂隙发育高度相关。他们发现,高冰崖的崩解速度比参数化方案所假设的更快,但动态减薄和向低冰厚度梯度区域的退缩阻止了失控退缩。这些观测表明,模型预测可能低估了冰崖崩解的次年度速率,但失稳的可能性将敏感地取决于额外变量,而不仅仅是冰崖高度。

▲ Abstract:

When calving cliffs at the margins of Earth’s ice sheets exceed a critical height, runaway retreat may be initiated in a process called the marine ice cliff instability. However, sufficiently tall ice cliffs have rarely been observed. To address this gap, we measured the characteristics of 15,330 ice cliffs across Earth’s ice sheet margins using laser altimetry. We show that cliff height is highly correlated with mélange thickness, water depth, and crevassing. We found that tall cliffs calve more rapidly than parameterizations assume, but dynamic thinning and retreat into regions with low ice thickness gradients prevent runaway retreat. These observations suggest that model projections may underestimate subannual rates of cliff calving, but that the potential for instability will depend sensitively on additional quantities, not cliff height alone.
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