Breaking of Internal Waves and Turbulent Dissipation in an Anticyclonic Mode Water Eddy
Breaking of Internal Waves and Turbulent Dissipation in an Anticyclonic Mode Water Eddy
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DOI：
10.1175/jpo-d-19-0168.1
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发表时间：
2020-07-01
影响因子：
3.5
通讯作者：
Naveira-Garabato, Alberto C.
中科院分区：
文献类型：
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作者：
Fernandez-Castro, Bieito;Evans, Dafydd Gwyn;Naveira-Garabato, Alberto C.
对为期 4 个月的滑翔机任务进行了分析，以评估北大西洋副热带西部边界的反气旋涡流中的湍流消散。涡流（半径约60 km）在100～450 m之间有一个低位涡核心，最大径向速度为0.5 ms(-1)，罗斯贝数接近-0.1。湍流耗散是根据滑翔机飞行模型得出的垂直水速推断出来的。涡流核心（ε 大约为 5 x 10(-10) W kg(-1)）中的耗散受到抑制，并在其下方增强（>10(-9) W kg(-1)）。耗散升高与垂直速度和压力扰动的准周期结构一致，表明内波是耗散的驱动因素。启发式光线追踪近似用于研究导致湍流耗散的波涡相互作用。射线追踪模拟与可能引起耗散的两种类型的波涡相互作用一致：涡流的相对涡度捕获近惯性波能，或内潮汐（在附近大陆坡产生）进入涡流剪切的关键层。后一种情况表明，表征海洋盆地西部边界的强烈中尺度场可能充当控制内潮汐传播到盆地内部的“渗漏墙”。
A4-month glider mission was analyzed to assess turbulent dissipation in an anticyclonic eddy at the western boundary of the subtropical North Atlantic. The eddy (radius approximate to 60 km) had a core of low potential vorticity between 100 and 450 m, with maximum radial velocities of 0.5ms(-1) and Rossby number approximate to -0.1. Turbulent dissipation was inferred from vertical water velocities derived from the glider flight model. Dissipation was suppressed in the eddy core (epsilon approximate to 5 x 10(-10) W kg(-1)) and enhanced below it (>10(-9) W kg(-1)). Elevated dissipation was coincident with quasiperiodic structures in the vertical velocity and pressure perturbations, suggesting internal waves as the drivers of dissipation. Aheuristic ray-tracing approximation was used to investigate the wave-eddy interactions leading to turbulent dissipation. Ray-tracing simulations were consistent with two types of wave-eddy interactions that may induce dissipation: the trapping of near-inertial wave energy by the eddy's relative vorticity, or the entry of an internal tide (generated at the nearby continental slope) to a critical layer in the eddy shear. The latter scenario suggests that the intense mesoscale field characterizing the western boundaries of ocean basins might act as a "leaky wall'' controlling the propagation of internal tides into the basin's interior.