Buoyant freshwater released at depth from under Greenland's marine‐terminating glaciers gives rise to vigorous buoyant discharge plumes adjacent to the termini. The water mass found down fjord formed by mixing of buoyant subglacial freshwater and ambient fjord water and subsequent modification by glacial ice melt in the ice mélange is referred to as subglacial water. It substantially affects both the physical and chemical properties of the fjords' marine environment. Despite the importance of this freshwater source, many uncertainties remain regarding its transformation and detection. Here we present observations close to a marine‐terminating glacier in a fjord with substantial ice mélange and follow the down‐fjord changes of the subglacial discharge plume. Heat brought to the surface by entrainment of warm ambient fjord water into the rising plume causes intense melting of the ice mélange close to the plume pool. This results in an increase of glacial ice melt fraction to total glacial meltwater from 1–2% in the plume pool to ~18% eleven kilometers down‐fjord, with the largest increase being observed within the first few kilometers. Down‐fjord of the ice mélange two temperature minima bound the layer containing subglacial water. The upper bound is linked to the adjacent ice mélange and down‐fjord runoff sources, whereas the lower bound is linked to the stratification of the ambient water. We show that similar bounds can be observed in other marine‐terminating glacier fjords along West Greenland that contain an ice mélange, suggesting that similar processes work in other fjords.

中文翻译：

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西格陵兰峡湾冰杂冰下的冰下排放及其向下的峡湾改造

从格陵兰岛的海洋终止冰川下方深处释放的浮力淡水会在靠近终点的地方产生剧烈的浮力羽流。由浮力的冰川下淡水和周围的峡湾水混合形成的峡湾下的水团，其后通过冰混合物中的冰川冰融化而变质，被称为冰川下水。它极大地影响了峡湾海洋环境的物理和化学性质。尽管这种淡水源很重要，但其转化和检测仍存在许多不确定性。在这里，我们观察到在冰雪混杂的峡湾中靠近海洋终止冰川的观测结果，并观察了冰川下泄流羽流的峡湾变化。由于温暖的环境峡湾水夹带进入上升的羽流而带到地表的热量导致靠近羽流池的冰混杂物强烈融化。这导致冰川冰融化分数相对于冰川融水的总量从羽流池中的1-2％增加到11公里下峡湾的〜18％，最大的增长出现在前几公里之内。冰川的下峡湾的两个温度最低限度限制了含有冰河水的层。上限与相邻的冰混杂物和峡湾径流源有关，而下限与环境水的分层有关。我们表明，在西格陵兰沿岸的其他海底冰川峡湾中也可以观察到类似的边界，其中包含冰混杂的冰山，这表明在其他峡湾中也可以使用类似的过程。