Abstract Marine outlet glaciers on Greenland are retreating, yet it is unclear if the recent fast retreat will persist, and how atmosphere and ocean warming will impact future retreat. We show how a marine outlet glacier in Hardangerfjorden retreated rapidly in response to the abrupt warming following the Younger Dryas cold period (approximately 11,600 years before present). This almost 1000 m deep fjord, with several sills at 300–500 m depth, hosted a 175 km long outlet glacier at the western rim of the Scandinavian Ice Sheet. We use a dynamic ice-flow model constrained by well-dated terminal and lateral moraines to simulate the reconstructed 500-year retreat of Hardangerfjorden glacier. The model includes an idealized oceanic and atmospheric forcing based on reconstructions, but excludes the surface mass balance-elevation feedback. Our simulations show a highly episodic retreat driven by surface melt and warming fjord waters, paced by the fjord bathymetry. Warming air and ocean temperatures by 4–5 °C during the period of retreat result in a 125-km retreat of Hardangerfjorden glacier in 500 years. Retreat rates throughout the deglaciation vary by an order of magnitude from 50 to 2500 m a−1, generally close to 200 m a−1, punctuated by brief events of swift retreat exceeding 500 m a−1, each event lasting a few decades. We show that the fastest retreat rates occur in regions of the bed with the largest retrograde slopes; ice shelf length and fjord water depth is less important. Our results have implications for modern glacial fjord settings similar to Hardangerfjorden, where high retreat rates have been observed. Our findings imply that increasing air temperatures and warming subsurface waters in Greenland fjords will continue to drive extensive retreat of marine outlet glaciers. However, the recent high retreat rates are not expected to be sustained for longer than a few decades due to constraints by the fjord bathymetry.

中文翻译：

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斯堪的纳维亚海洋出口冰川因末次冰川终止变暖而迅速退缩

摘要 格陵兰岛海洋出口冰川正在退缩，但近期的快速退缩是否会持续，大气和海洋变暖对未来退缩的影响尚不清楚。我们展示了哈当厄尔峡湾的海洋出口冰川如何响应新仙女木寒冷时期（大约在现在之前的 11,600 年之前）的突然变暖而迅速退缩。这个近 1000 m 深的峡湾在 300-500 m 深有几个基石，在斯堪的纳维亚冰盖的西缘有一条 175 公里长的出口冰川。我们使用受年代久远的终端和侧冰碛约束的动态冰流模型来模拟重建的哈当厄尔峡湾冰川 500 年退缩。该模型包括基于重建的理想化海洋和大气强迫，但不包括表面质量平衡-高程反馈。我们的模拟显示了由地表融化和变暖的峡湾水域驱动的高度间歇性撤退，由峡湾测深仪控制。在退缩期间，空气和海洋温度升高 4-5 °C，导致哈当厄尔峡湾冰川在 500 年内退缩 125 公里。整个冰川消退的退缩率在 50 到 2500 ma-1 的数量级之间变化，通常接近 200 ma-1，偶尔会出现超过 500 ma-1 的快速退缩事件，每次事件持续几十年。我们表明，最快的后退率发生在具有最大逆行坡度的床层区域；冰架长度和峡湾水深不太重要。我们的结果对类似于哈当厄尔峡湾的现代冰川峡湾环境具有影响，在那里观察到了高退缩率。我们的研究结果表明，格陵兰峡湾气温升高和地下水变暖将继续推动海洋出口冰川的大规模消退。然而，由于峡湾水深测量的限制，预计最近的高撤退率不会持续超过几十年。