Shear, Stability and Mixing within the Ice-Shelf-Ocean Boundary Current
Shear, Stability and Mixing within the Ice-Shelf-Ocean Boundary Current
复制标题
冰架-海洋边界流内的剪切、稳定性和混合
DOI：
10.1175/jpo-d-20-0096.1
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发表时间：
2021
影响因子：
3.5
通讯作者：
Jenkins A
中科院分区：
文献类型：
--
作者：
Jenkins A
当倾斜的冰架底部融化到海洋中时，它会引起静稳定的层结和浮力强迫的剪切流，沿界面沿着流动。了解这些相互竞争的效应如何影响边界流的动力稳定性，是量化从远场海洋到冰的湍流热传递的关键。剪切，稳定性和混合之间的密切耦合的影响进行了探讨与援助的一维数值模型，模拟密度和电流剖面垂直于冰。扩散率和粘度的确定使用的湍流边界层内的混合长度模型和经验函数的梯度Richardson数在下面的分层层。从休息开始，边界电流最初强烈分层和动态稳定，慢慢增厚的融水扩散远离界面。最终，目前进入第二阶段，动力不稳定产生一个相对良好的混合，湍流层附近的冰，而下面的电流最大，强烈的分层抑制混合在该地区的反向剪切。在弱浮力强迫下，初始动力不稳定性发展的时间尺度可以是几个月或更长，但实际上总是存在的背景流提供了额外的电流剪切，大大加速了这一过程。当冰架底部足够陡峭时，可以达到第三阶段，动力不稳定性超出边界层延伸到地转流区域，产生一个边缘稳定的密度跃层，通过该密度跃层，热通量是冰-海洋界面斜率的简单函数。
When the inclined base of an ice shelf melts into the ocean, it induces both a statically stable stratification and a buoyancy-forced, sheared flow along the interface. Understanding how those competing effects influence the dynamical stability of the boundary current is the key to quantifying the turbulent transfer of heat from far-field ocean to ice. The implications of the close coupling between shear, stability, and mixing are explored with the aid of a one-dimensional numerical model that simulates density and current profiles perpendicular to the ice. Diffusivity and viscosity are determined using a mixing length model within the turbulent boundary layer and empirical functions of the gradient Richardson number in the stratified layer below. Starting from rest, the boundary current is initially strongly stratified and dynamically stable, slowly thickening as meltwater diffuses away from the interface. Eventually, the current enters a second phase where dynamical instability generates a relatively well-mixed, turbulent layer adjacent to the ice, while beneath the current maximum, strong stratification suppresses mixing in the region of reverse shear. Under weak buoyancy forcing the time scale for development of the initial dynamical instability can be months or longer, but background flows, which are always present in reality, provide additional current shear that greatly accelerates the process. A third phase can be reached when the ice shelf base is sufficiently steep, with dynamical instability extending beyond the boundary layer into regions of geostrophic flow, generating a marginally stable pycnocline through which the heat flux is a simple function of ice–ocean interfacial slope.
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DOI：
--
发表时间：
2007
期刊：
影响因子：
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作者：
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作者：
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影响因子：
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作者：
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作者：
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