Internal tides and turbulent mixing observed in the Bussol Strait
Internal tides and turbulent mixing observed in the Bussol Strait
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DOI：
10.1016/j.pocean.2014.04.009
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发表时间：
2014-08
影响因子：
4.1
通讯作者：
Yuki Tanaka;I. Yasuda;S. Osafune;Takahiro Tanaka;J. Nishioka;Y. Volkov
中科院分区：
文献类型：
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作者：
Yuki Tanaka;I. Yasuda;S. Osafune;Takahiro Tanaka;J. Nishioka;Y. Volkov
重复观测约24小时的水文，流速，和微观结构进行了在三个站周围的海山中的布索尔海峡，最深和最宽的千岛海峡，揭示空间和时间的内部潮汐和相关的湍流混合的变化。据发现，等密度线位移占主导地位的昼夜潮汐分量，这表明相位差（即，时间滞后）之间的三个站，可以解释为第一模式的地形捕获波（TTW）沿顺时针方向传播的海山。此外，在位于海峡中心附近的站点，能量耗散率是最大的，等密度线和速度的日变化被放大向海底，第一模态TTW的垂直结构相一致。当第一模态TTW组成的日潮流从鄂霍次克海流向北太平洋时，在该测站观测到了深层强烈的湍流混合，其能量耗散率超过10-6 m2 s-3，径向扩散率超过10-1 m2 s-1，增强了平均流。这些空间和时间的变化模式被证实是由以前的数值模式成功地再现的等密度线和速度，部分湍流混合。然而，总能量耗散率是由高达3-10的一个因素，比预测的数值模型，虽然观测在春潮期间进行，这表明，实际的diapycnal混合是整体弱于以前的模型估计和/或非常强的混合发生在高度本地化的地区。
Repeated observations with a period of about 24 h of hydrography, current velocity, and microstructures were performed at three stations surrounding a seamount in the middle of the Bussol Strait, the deepest and widest one of the Kuril Straits, to reveal spatial and temporal variability of internal tides and associated turbulent mixing. It is found that isopycnal displacements are dominated by diurnal tidal components, which show phase differences (namely, time lags) between the three stations that can be explained by a first mode topographically trapped wave (TTW) propagating clockwise around the seamount. Furthermore, at the station located near the center of the strait where energy dissipation rates are largest, diurnal variations of isopycnals and velocities are amplified toward the ocean bottom, consistent with the vertical structure of the first mode TTW. At that station, vigorous turbulent mixing with the energy dissipation rate exceeding 10-6 m 2 s-3 and diapycnal diffusivity exceeding 10-1 m 2 s-1 was observed in deep layers when the diurnal tidal current consisting of the first mode TTW flows from the Okhotsk Sea to the North Pacific, enhancing the mean current. These spatial and temporal variation patterns are confirmed to be reproduced by a previous numerical model successfully for the isopycnals and velocities, and partially for the turbulent mixing. The total energy dissipation rate is, however, by up to a factor of 3–10 smaller than predicted by the numerical model although the observations were performed during spring tides, suggesting that the actual diapycnal mixing is overall weaker than the previous model estimate and/or that extremely strong mixing occurs within highly localized areas.