Dynamics of an idealized Beaufort Gyre: 1. The effect of a small beta and lack of western boundaries: BEAUFORT GYRE DYNAMICS
Dynamics of an idealized Beaufort Gyre: 1. The effect of a small beta and lack of western boundaries: BEAUFORT GYRE DYNAMICS
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理想化波弗特环流的动力学： 1. 小贝塔和缺乏西部边界的影响：波弗特环流动力学
DOI：
10.1002/2015jc011296
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Lin, Xiaopei
中科院分区：
文献类型：
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作者：
Yang, Jiayan;Proshutinsky, Andrey;Lin, Xiaopei
北冰洋的博福特环流在动力学的一些主要方面与典型的中纬度环流不同。首先，它位于一个没有西部边界的盆地，而西部边界对于关闭中纬度环流是必不可少的。第二，科里奥利参数的梯度β很小，因此Sverdrup平衡的有效性是不确定的。在本文中，我们使用一个理想化的两层模型来研究与这两个问题相关的几个过程。在内部具有闭合地转等值线的圆形海盆中，上层涡度的变率主要由涡旋控制。但在时均环流中，海盆内部的主要动力平衡是风应力旋度和涡度通量之间的平衡。在边缘电流强的边界上，摩擦力矩沿着变得重要。结果表明，在无边界的圆形盆地中，β值的小影响较小。环流对纬向边界的存在更为敏感。当在模式的中心和边缘之间插入一个半岛时，时间平均环流大大减弱。(One半岛的一侧在动力学上相当于中纬度西部边界。）当存在纬向边界时，涡旋对β的敏感性也显著增加。次表层海脊对作为边界的环流也有类似的影响，这表明这种地形特征在某种程度上可以替代西部边界的动力作用。
The Beaufort Gyre in the Arctic Ocean differs from a typical moderate‐latitude gyre in some major aspects of its dynamics. First, it is located in a basin without a western boundary, which is essential for closing midlatitude circulations. Second, the gradient in Coriolis parameter,β, is small and so the validity of the Sverdrup balance is uncertain. In this paper, we use an idealized two‐layer model to examine several processes that are related to these two issues. In a circular basin with closed geostrophic contours in interior, the variability of vorticity in the upper layer is dominated by eddies. But in the time‐mean circulation, the main dynamical balance in the basin's interior is between the curl of wind stress and the eddy vorticity fluxes. The torque of friction becomes important along the boundary where the rim current is strong. It is found that the smallness ofβhas only a relatively small impact in a circular basin without a meridional boundary. The gyre is considerably more sensitive to the existence of a meridional boundary. The time‐mean circulation weakens considerably when a peninsula is inserted between the model's center and the rim. (One side of the peninsula is dynamically equivalent to a midlatitude western boundary.) The gyre's sensitivity toβhas also increased significantly when a meridional boundary is present. Subsurface ridges have similar effects on the gyre as a boundary, indicating that such topographic features may substitute, to some extents, the dynamical role of a western boundary.