A numerical investigation on the energetics of a current along an ice-covered continental slope
A numerical investigation on the energetics of a current along an ice-covered continental slope
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DOI：
10.5194/os-19-289-2023
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发表时间：
2023-03
期刊：
影响因子：
3.2
通讯作者：
Hengling Leng;Hailun He;M. Spall
中科院分区：
文献类型：
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作者：
Hengling Leng;Hailun He;M. Spall
抽象的。楚科奇陆坡流是一个沿楚科奇陆坡沿着向西流动的水流，它将太平洋水从楚科奇大陆架带入加拿大盆地，并帮助确定区域水文结构和生态系统。利用一组理想化原始方程数值模式的实验，我们研究了斜坡流在冰封期的能量学。数值计算表明，冰摩擦抑制了表面涡的增长，而在中间深度的扰动可以发展成涡，与线性不稳定性分析一致。然而，由于冰应力是空间可变的，它是能够驱动埃克曼抽水，以减少可用的势能（APE）和动能的平均流和中尺度涡超过100米的垂直尺度，以及外的摩擦埃克曼层。APE变化的速率由垂直密度通量决定，当冰引起的Ekman泵送使较轻（较重）的水向上（向下）平流时，垂直密度通量为负。标度分析表明，Ekman抽吸作用对大尺度流场APE的释放起主导作用，但当平均流场的水平尺度为斜压形变半径且涡动速度与平均流场速度相当时，斜压不稳定的作用也很重要。我们的数值计算结果突出了冰摩擦力的斜坡流和涡的能量的重要性，这可能是相关的其他冰覆盖的地区。
Abstract. The Chukchi Slope Current is a westward-flowing current along the Chukchi slope, which carries Pacific-origin water from the Chukchi shelf into the Canada Basin and helps set the regional hydrographic structure and ecosystem. Using a set of experiments with an idealized primitive equation numerical model, we investigate the energetics of the slope current during the ice-covered period. Numerical calculations show that the growth of surface eddies is suppressed by the ice friction, while perturbations at mid-depths can grow into eddies, consistent with linear instability analysis. However, because the ice stress is spatially variable, it is able to drive Ekman pumping to decrease the available potential energy (APE) and kinetic energy of both the mean flow and mesoscale eddies over a vertical scale of 100 m, well outside the frictional Ekman layer. The rate at which the APE changes is determined by the vertical density flux, which is negative as the ice-induced Ekman pumping advects lighter (denser) water upward (downward). A scaling analysis shows that Ekman pumping will dominate the release of APE for large-scale flows, but the effect of baroclinic instability is also important when the horizontal scale of the mean flow is the baroclinic deformation radius and the eddy velocity is comparable to the mean flow velocity. Our numerical results highlight the importance of ice friction in the energetics of the slope current and eddies, and this may be relevant to other ice-covered regions.