On the Settling Depth of Meltwater Escaping from beneath Antarctic Ice Shelves
On the Settling Depth of Meltwater Escaping from beneath Antarctic Ice Shelves
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DOI：
10.1175/jpo-d-20-0286.1
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发表时间：
2021-07-01
影响因子：
3.5
通讯作者：
Ramadhan, Ali
中科院分区：
文献类型：
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作者：
Arnscheidt, Constantin W.;Marshall, John;Ramadhan, Ali
南极冰川融水被认为在确定大规模南大洋气候趋势方面发挥着重要作用，但最近的建模工作并没有很好地理解其在水柱中的垂直分布是如何设定的。为了纠正这个问题，我们在这里对从南极冰架下方逃逸出来的浮力融水羽流的上升进行了新的大涡模拟。我们发现融水的沉降深度主要是源头每单位宽度的浮力和环境分层的函数，这与湍流浮力羽流的经典理论一致，并且与之前提出离心不稳定性的重要作用的研究形成鲜明对比。我们的结果进一步强调了分层中局部变异性所发挥的重要作用；这有助于解释观察到的松岛冰川附近垂直融水分布的年际变化。由于不同南极冰架的质量损失率和环境条件存在巨大差异，融水沉降深度的动态参数化对于准确模拟变暖世界中的高纬度气候可能至关重要；我们讨论这项工作之后如何发展，以及剩下的挑战在哪里。
Antarctic glacial meltwater is thought to play an important role in determining large-scale Southern Ocean climate trends, yet recent modeling efforts have proceeded without a good understanding of how its vertical distribution in the water column is set. To rectify this, here we conduct new large-eddy simulations of the ascent of a buoyant meltwater plume after its escape from beneath an Antarctic ice shelf. We find that the meltwater's settling depth is primarily a function of the buoyancy forcing per unit width of the source and the ambient stratification, consistent with the classical theory of turbulent buoyant plumes and in contrast to previous work that suggested an important role for centrifugal instability. Our results further highlight the significant role played by localized variability in stratification; this helps explain observed interannual variability in the vertical meltwater distribution near Pine Island Glacier. Because of the vast heterogeneity in mass loss rates and ambient conditions at different Antarctic ice shelves, a dynamic parameterization of meltwater settling depth may be crucial for accurately simulating high-latitude climate in a warming world; we discuss how this may be developed following this work, and where the remaining challenges lie.