Temporal Evolution of a Geostrophic Current under Sea Ice: Analytical and Numerical Solutions
Temporal Evolution of a Geostrophic Current under Sea Ice: Analytical and Numerical Solutions
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DOI：
10.1175/jpo-d-21-0242.1
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发表时间：
2022-03
影响因子：
3.5
通讯作者：
Hengling Leng;M. Spall;X. Bai
中科院分区：
文献类型：
--
作者：
Hengling Leng;M. Spall;X. Bai
本文利用一个简化的准地转（QG）分析模式和一个理想化的数值模式，研究了不均匀冰-海应力对海冰下地转流时间演变的影响。在QG模式中，地转速度的趋势是垂直速度横向梯度的函数，并进一步与冰-海应力联系起来，考虑了表面边界层。结合解析解和数值解，我们证明了冰和最初的表面增强，横向剪切地转流之间的不均匀应力可以驱动翻转环流触发位移的等密度线和修改的地转速度的垂直结构。当近地表的等密度线向与深层等密度线相反的方向倾斜时，就产生了一个地下速度核（通过地转设置）。这一机制应有助于理解观测中看到的楚科奇海和博福特海边缘次表层洋流的形成。此外，我们的解决方案揭示了从底部延伸到中间深度的反向流动，这表明冰引起的翻转环流可能会影响北冰洋深层的电流，如大西洋水边界电流。
A simplified quasigeostrophic (QG) analytical model together with an idealized numerical model are used to study the effect of uneven ice-ocean stress on the temporal evolution of the geostrophic current under sea ice. The tendency of the geostrophic velocity in the QG model is given as a function of the lateral gradient of vertical velocity and is further related to the ice-ocean stress with consideration of a surface boundary layer. Combining the analytical and numerical solutions, we demonstrate that the uneven stress between the ice and an initially surface-intensified, laterally sheared geostrophic current can drive an overturning circulation to trigger the displacement of isopycnals and modify the vertical structure of the geostrophic velocity. When the near-surface isopycnals become tilted in the opposite direction to the deeper ones, a subsurface velocity core is generated (via geostrophic set up). This mechanism should help understand the formation of subsurface currents in the edge of Chukchi and Beaufort Seas seen in observations. Furthermore, our solutions reveal a reversed flow extending from the bottom to the mid-depth, suggesting that the ice-induced overturning circulation potentially influences the currents in the deep layers of the Arctic Ocean, such as the Atlantic Water boundary current.