Geological and glacial-hydrologic controls on chemical weathering in the subglacial environment
Geological and glacial-hydrologic controls on chemical weathering in the subglacial environment
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DOI：
10.1017/aog.2023.56
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发表时间：
2022-09
影响因子：
2.9
通讯作者：
J. Graly;Soroush Rezvanbehbahani
中科院分区：
文献类型：
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作者：
J. Graly;Soroush Rezvanbehbahani
通过对冰下钻孔和排放冰下水的主要离子化学的比较，揭示了三种根本不同的冰川水化学状态。高山冰川的冰下水与格陵兰岛或南极洲的冰下水具有截然不同的化学物质。格陵兰和南极洲也从根本上不同，格陵兰冰盖水域，至少在夏季融化季节，保持稀释，不受饱和反应的影响，而南极冰盖水域由一系列饱和状态控制。一些南极水域形成浓缩的卤水，能够将冰点降低10摄氏度。虽然这些水域只在很少出现的地方直接取样，但来自德文冰帽和格陵兰的地球物理观测表明，在冰层薄且移动缓慢的位置，冰川床上有液态水，否则可能会出现冷床。这增加了这样一种可能性，即造岩的冰下卤水可能广泛存在，我们现有的冰下水化学测量可能因自由排放水的季节性采样而产生偏差。冰盖下各种冰下环境的可能性表明，需要新的、雄心勃勃的采样方案，以确定难以获取的冰下水域的特征，并量化其对冰川动力学、地球生物学和全球地球化学循环的影响。
Abstract A comparison of major ion chemistry of subglacial boreholes and discharging subglacial waters reveals three fundamentally different glacier hydrochemical regimes. Subglacial waters from alpine glaciers have chemistry distinct from the subglacial waters of Greenland or Antarctica. Greenland and Antarctica also differ fundamentally from each other, with Greenland Ice Sheet waters, at least during the summer melt season, remaining dilute and unaffected by saturation reactions and Antarctic Ice Sheet waters controlled by a range of saturation states. Some Antarctic waters form concentrated brines, capable of depressing the freezing point by >10°C. While these waters have only been directly sampled where they rarely emerge, geophysical observations from Devon Ice Cap and Greenland show liquid water at the glacier bed in locations where ice is thin and slowly moving and a cold bed is otherwise expected. This raises the possibility that lithogenic subglacial brines could be widespread and that our existing subglacial hydrochemical measurements might be biased by seasonal sampling of freely discharging water. The potential for diverse ranges of subglacial environments under ice sheets suggests the need for new and ambitious sampling programs to characterize difficult to access subglacial waters and quantify their impact on glacier dynamics, geobiology and global geochemical cycling.