Foss Ø, Maton J, Moholdt G, Schmidt L S, Sutherland D A, Fer I, Nilsen F, Kohler J, Sundfjord A
Norwegian Polar Institute, Tromsø, Norway.
University of Oslo, Oslo, Norway.
Nat Commun. 2024 Dec 2;15(1):10460. doi: 10.1038/s41467-024-54825-7.
Glaciers in the Arctic have lost considerable mass during the last two decades. About a third of the glaciers by area drains into the ocean, yet the mechanisms and drivers governing mass loss at glacier calving fronts are poorly constrained in part due to few long-term glacier-ocean observations. Here, we combine a detailed satellite-based record of calving front ablation for Austfonna, the largest ice cap on Svalbard, with in-situ ocean records from an offshore mooring and modelled freshwater runoff for the period 2018-2022. We show that submarine melting and calving occur almost exclusively in autumn for all types of outlet glaciers, even for the surging and fast-flowing glacier Storisstraumen. Ocean temperature controls the observed frontal ablation, whereas subglacial runoff of surface meltwater appears to have little direct impact on the total ablation. The seasonal warming of the offshore waters varies both in magnitude, depth and timing, suggesting a complex interplay between inflowing Atlantic-influenced water at depth and seasonally warmed surface water in the Barents Sea. The immediate response of frontal ablation to seasonal ocean warming suggests that marine-terminating glaciers in high Arctic regions exposed to Atlantification are prone to rapid changes that should be accounted for in future glacier projections.
在过去二十年中，北极的冰川损失了大量质量。约三分之一的冰川区域流入海洋，但由于长期的冰川 - 海洋观测数据较少，控制冰川崩解前沿质量损失的机制和驱动因素仍存在很大不确定性。在此，我们将斯瓦尔巴群岛最大冰盖奥斯特方纳（Austfonna）崩解前沿消融的详细卫星记录，与2018 - 2022年期间近海系泊的现场海洋记录以及模拟淡水径流相结合。我们发现，对于所有类型的入海冰川，甚至是涌动和快速流动的斯托里斯斯特劳门（Storisstraumen）冰川，海底融化和崩解几乎都只发生在秋季。海洋温度控制着观测到的前沿消融，而表层融水的冰下径流似乎对总消融量没有直接影响。近海海域的季节性变暖在幅度、深度和时间上都有所不同，这表明深层受大西洋影响的流入水与巴伦支海季节性变暖的表层水之间存在复杂的相互作用。前沿消融对季节性海洋变暖的即时响应表明，受大西洋化影响的高北极地区的海洋终端冰川容易发生快速变化——这一点在未来的冰川预测中应予以考虑。
