Dynamics of Eddies Generated by Sea Ice Leads
Dynamics of Eddies Generated by Sea Ice Leads
复制标题
DOI：
10.1175/jpo-d-20-0169.1
复制
发表时间：
2021-07
影响因子：
3.5
通讯作者：
K. Cohanim;Ken Zhao;A. Stewart
中科院分区：
文献类型：
--
作者：
K. Cohanim;Ken Zhao;A. Stewart
海冰覆盖区域的大气和海洋之间的相互作用主要集中在海冰浮冰之间的狭长开口处。这些引线中的重新冻结和盐水排斥会注入盐，这在维持极地盐跃层中起着关键作用。注入的盐形成密集的羽流，随后变得斜压不稳定，产生亚中尺度涡流，促进盐异常的水平扩散。然而，目前尚不清楚层结和铅的哪些特性对铅输入盐异常的垂直和水平扩散影响最大。在这项研究中，使用一套理想化的数值模拟研究了混合层和涡流过程引起的铅注入浮力异常的传播。动力学理论对模拟进行了补充，预测羽流对流深度、水平涡流传递系数和涡流动能作为环境分层和铅特性的函数。结果表明，混合层温度和盐度预算可以准确预测浮力异常的垂直渗透，直到斜压不稳定开始（约 3 天）。随后，这些浮力异常通过涡流水平传播。水平涡流扩散率通过混合长度尺度准确预测，速度尺度由下沉盐羽释放的势能设定，长度尺度由环境层结的变形半径设定。这些发现表明，引线的间歇性打开可以有效地在极地盐跃层中填充直径约为 10 公里的亚中尺度相干涡旋，并为参数化其对盐度异常水平重新分布的影响提供了一步。
Interaction between the atmosphere and ocean in sea ice-covered regions is largely concentrated in leads, which are long, narrow openings between sea ice floes. Refreezing and brine rejection in these leads injects salt that plays a key role in maintaining the polar halocline. The injected salt forms dense plumes that subsequently become baroclinically unstable, producing submesoscale eddies that facilitate horizontal spreading of the salt anomalies. However, it remains unclear which properties of the stratification and leads most strongly influence the vertical and horizontal spreading of lead-input salt anomalies. In this study, the spread of lead-injected buoyancy anomalies by mixed layer and eddy processes are investigated using a suite of idealized numerical simulations. The simulations are complemented by dynamical theories that predict the plume convection depth, horizontal eddy transfer coefficient and eddy kinetic energy as functions of the ambient stratification and lead properties. It is shown that vertical penetration of buoyancy anomalies is accurately predicted by a mixed layer temperature and salinity budget until the onset of baroclinic instability (~3 days). Subsequently, these buoyancy anomalies are spread horizontally by eddies. The horizontal eddy diffusivity is accurately predicted by a mixing length scaling, with a velocity scale set by the potential energy released by the sinking salt plume and a length scale set by the deformation radius of the ambient stratification. These findings indicate that the intermittent opening of leads can efficiently populate the polar halocline with submesoscale coherent vortices with diameters of around 10 km, and provide a step toward parameterizing their effect on the horizontal redistribution of salinity anomalies.