A probabilistic framework for quantifying the role of anthropogenic climate change in marine-terminating glacier retreats
A probabilistic framework for quantifying the role of anthropogenic climate change in marine-terminating glacier retreats
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DOI：
10.5194/tc-16-2725-2022
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发表时间：
2022-07-13
期刊：
影响因子：
5.2
通讯作者：
Catania, Ginny
中科院分区：
文献类型：
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作者：
Christian, John Erich;Robel, Alexander A.;Catania, Ginny
近几十年来，许多海洋终止的出口冰川迅速消退，但这些变化尚未正式归因于人为气候变化。这种归因评估的一个关键挑战是，如果冰川终点受到测深高点的充分扰动，即使没有进一步的气候强迫，冰动力反馈也可能导致快速消退。因此，在存在内部气候变化的情况下，归因取决于了解这些快速撤退是否（或多久）可能仅由气候噪音引发。我们对理想化冰川的模拟表明，在嘈杂的气候中，快速消退是一种随机现象。因此，我们提出了一种概率归因方法，并提出了一个分析框架，该框架使用许多模拟的集合以及随机气候变化的独立实现。综合实验表明，百年规模的气候趋势大大增加了冰川快速退缩的可能性。这种效应取决于冰动力学整合强迫的时间尺度。对于具有不同地形的合成冰川群，我们发现外部趋势增加了群内引发的大规模退缩的数量，从而提供了区域归因的指标。我们的分析表明，正式的归因研究是容易处理的，应该进一步进行，以阐明人类在最近冰盖变化中的作用。我们强调，早期工业时代对冰川和气候状态的限制可能对此类研究至关重要。
Many marine-terminating outlet glaciers have retreated rapidly in recent decades, but these changes have not been formally attributed to anthropogenic climate change. A key challenge for such an attribution assessment is that if glacier termini are sufficiently perturbed from bathymetric highs, ice-dynamic feedbacks can cause rapid retreat even without further climate forcing. In the presence of internal climate variability, attribution thus depends on understanding whether (or how frequently) these rapid retreats could be triggered by climatic noise alone. Our simulations with idealized glaciers show that in a noisy climate, rapid retreat is a stochastic phenomenon. We therefore propose a probabilistic approach to attribution and present a framework for analysis that uses ensembles of many simulations with independent realizations of random climate variability. Synthetic experiments show that century-scale climate trends substantially increase the likelihood of rapid glacier retreat. This effect depends on the timescales over which ice dynamics integrate forcing. For a population of synthetic glaciers with different topographies, we find that external trends increase the number of large retreats triggered within the population, offering a metric for regional attribution. Our analyses suggest that formal attribution studies are tractable and should be further pursued to clarify the human role in recent ice-sheet change. We emphasize that early-industrial-era constraints on glacier and climate state are likely to be crucial for such studies.