Nonlinear influence of the Earth’s rotation on iceberg melting
Nonlinear influence of the Earth’s rotation on iceberg melting
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DOI：
10.1017/jfm.2018.798
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发表时间：
2018-11
影响因子：
3.7
通讯作者：
A. Meroni;C. McConnochie;C. Cenedese;B. Sutherland;K. Snow
中科院分区：
文献类型：
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作者：
A. Meroni;C. McConnochie;C. Cenedese;B. Sutherland;K. Snow
冰山崩解占南极和格陵兰冰盖质量损失的很大一部分。冰山融化会影响水的性质，从而影响海冰的形成、局部循环和生物活动。实验室实验研究了地球自转对冰山融化的影响以及冰山下方可能形成的泰勒柱（TC）。研究发现，在高罗斯比数 $Ro$ 下，当旋转与平流相比较弱时，冰山融化不受背景旋转的影响。随着 $Ro$ 的降低，熔化速率呈现增加趋势，预计 $Ro$ 非常低时会发生逆转。这种行为可以通过考虑冰山底部的综合水平速度来解释。对于中等$Ro$，形成部分TC，其有效阻塞加速了冰山其余部分下方的流动，这增加了融化速率，因为融化与流速成正比。预计在 $Ro$ 非常低的情况下，融化速率会降低，因为随着 TC 的扩展，流动加速区域会远离冰山底部。对于低自由流速度，冰融化产生的淡水引入了另一种动力学效应。据观察，存在一个阈值自由流速度，低于该阈值熔化速率是恒定的。这可以用冰山底部形成的重力流来解释，该重力流将冰山与自由流隔离并控制其融化。
The calving of icebergs accounts for a significant fraction of the mass loss from both the Antarctic and Greenland ice sheets. Iceberg melting affects the water properties impacting sea ice formation, local circulation and biological activity. Laboratory experiments have investigated the effects of the Earth’s rotation on iceberg melting and the possible formation of Taylor columns (TCs) underneath icebergs. It is found that at high Rossby number, $Ro$ , when rotation is weak compared to advection, iceberg melting is unaffected by the background rotation. As $Ro$ decreases, the melt rate shows an increasing trend, which is expected to reverse for very low $Ro$ . This behaviour is explained by considering the integrated horizontal velocity at the base of the iceberg. For moderate $Ro$ , a partial TC is formed and its effective blocking accelerates the flow under the remainder of the iceberg, which increases the melt rate since the melting is proportional to the flow velocity. It is expected that for very low $Ro$ the melt rate decreases because, with the expansion of the TC, the region of flow acceleration occurs away from the base of the iceberg. For low free stream velocity the freshwater produced by the ice melting introduces another dynamical effect. It is observed that there is a threshold free stream velocity below which the melt rate is constant. This is explained with the formation of a gravity current at the base of the iceberg that insulates it from the free flow and controls its melting.