Topographic vorticity generation, submesoscale instability and vortex street formation in the Gulf Stream
Topographic vorticity generation, submesoscale instability and vortex street formation in the Gulf Stream
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DOI：
10.1002/2015gl063731
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发表时间：
2015-05-28
影响因子：
5.2
通讯作者：
McWilliams, J. C.
中科院分区：
文献类型：
--
作者：
Gula, J.;Molemaker, M. J.;McWilliams, J. C.
沿着南大西洋湾的墨西哥湾流经常会出现曲流和漩涡。本文采用高分辨率模拟分析了佛罗里达海峡出口处墨西哥湾流气旋侧亚中尺度涡旋形成的不稳定过程。由于大陆坡的地形阻力，湾流气旋侧的正相对涡度和位涡度在海峡内强烈增强。底部阻力通过在倾斜湍流底边界层内产生大的正垂直涡度值来放大气旋切变。海峡下游水流由不稳定转为水平剪切不稳定，向上卷起，形成一条亚中尺度涡旋街。当涡旋沿着大陆架向北传播时，它们会扩大，在那里它们会产生巨大的垂直位移，并加强跨大陆架的交换。
Meanders and eddies are routinely observed in the Gulf Stream along the South Atlantic Bight. We analyze here the instability processes that lead to the formation of submesoscale eddies on the cyclonic side of the Gulf Stream at the exit of the Florida Straits using very high resolution realistic simulations. The positive relative vorticity and potential vorticity on the cyclonic side of the Gulf Stream are strongly intensified in the Straits due to topographic drag along the continental slope. The bottom drag amplifies the cyclonic shear by generating large positive vertical vorticity values within the sloped turbulent bottom boundary layer. Downstream from the Straits the current becomes unstable to horizontal shear instability, rolls up, and forms a street of submesoscale vortices. The vortices expand as they propagate northward along the shelf, where they can generate large vertical displacements and enhance cross-shelf exchanges.