Subsurface iceberg melt key to Greenland fjord freshwater budget
Subsurface iceberg melt key to Greenland fjord freshwater budget
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DOI：
10.1038/s41561-017-0018-z
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发表时间：
2018-01-01
影响因子：
18.3
通讯作者：
Straneo, F.
中科院分区：
文献类型：
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作者：
Moon, T.;Sutherland, D. A.;Straneo, F.
格陵兰冰盖的液态淡水通量在局部、区域和全流域范围内影响海水性质和环流，并伴有相关的生物圈效应。然而，确切的影响取决于淡水释放的量、时间和位置，而这些情况人们知之甚少。特别是，冰山的转化过程尚未得到很好的理解，而冰山约占冰盖质量转化为液态淡水损失的30% - 50%。在此，我们利用一个能解析冰山水下融化的冰山融化模型，估算了格陵兰岛东南部海尔海姆 - 瑟米利克冰川 - 峡湾系统淡水通量的时空分布。通过估算所有淡水源的季节性变化，我们定量地证实了冰山融化是这类系统中最大的年度淡水源。我们还表明，68% - 78%的冰山融水在20米深度以下释放，并且从季节上看，与通常的模型假设相反，大约40% - 100%的融水可能会留在深处。冰山融化在所有其他淡水源达到峰值两个月后才达到峰值。我们的方法为评估任何潮水系统中的单个淡水源提供了一个框架，我们的研究结果尤其适用于格陵兰岛固体冰排放量大的沿海地区。
Liquid freshwater fluxes from the Greenland ice sheet affect ocean water properties and circulation on local, regional and basin-wide scales, with associated biosphere effects. The exact impact, however, depends on the volume, timing and location of freshwater releases, which are poorly known. In particular, the transformation of icebergs, which make up roughly 30-50% of the loss of the ice-sheet mass to liquid freshwater, is not well understood. Here we estimate the spatial and temporal distribution of the freshwater flux for the Helheim-Sermilikg lacier-fjord system in southeast Greenland using an iceberg-melt model that resolves the subsurface iceberg melt. By estimating seasonal variations in all the freshwater sources, we confirm quantitatively that iceberg melt is the largest annual freshwater source in this system type. We also show that 68-78% of the iceberg melt is released below a depth of 20 m and, seasonally, about 40-100% of that melt is likely to remain at depth, in contrast with the usual model assumptions. Iceberg melt also peaks two months after all the other freshwater sources peak. Our methods provide a framework to assess individual freshwater sources in any tidewater system, and our results are particularly applicable to coastal regions with a high solid-ice discharge in Greenland.