Enhanced Diapycnal Mixing due to Near-Inertial Internal Waves Propagating through an Anticyclonic Eddy in the Ice-Free Chukchi Plateau
Enhanced Diapycnal Mixing due to Near-Inertial Internal Waves Propagating through an Anticyclonic Eddy in the Ice-Free Chukchi Plateau
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DOI：
10.1175/jpo-d-15-0150.1
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发表时间：
2016-08-01
影响因子：
3.5
通讯作者：
Oshima, Kazuhiro
中科院分区：
文献类型：
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作者：
Kawaguchi, Yusuke;Nishino, Shigeto;Oshima, Kazuhiro
众所周知，北冰洋在与内波相关的湍流动能（TKE）方面是静止的。为了调查北冰洋季节性无冰楚科奇高原TKE的现状，本研究于2014年9月进行了为期3周的定点观测（FPO），使用重复的微观结构，水文和海流测量。在FPO计划期间，微结构观测在移动穿过FPO站的反气旋涡流的横断面期间检测到TKE耗散率的显著峰值。特别是，在较低的盐跃层，附近的临界水平，达到10 - 28 Wkg-21的顺序。ADCP测得的电流显示出充满活力的近惯性内波（NIWs）通过在反气旋的顶部和底部的分层传播。水平速度谱分析表明，波浪能量几乎向下传播，其流速幅值可达10 cm s（-1）左右。的WKB缩放，结合垂直变化的相对涡度，表明增加波能量附近的两个pycerkline与递减的群速度在相应的深度。利用观测到的近惯性速度和浮力频率的细尺度参数化成功地再现了观测到的湍流特征，支持了近惯性动能可以有效地耗散到临界层附近的湍流中。根据一个混合层平板模型，在第一周经过的快速移动的风暴可能将大部分NIW动能传递到地表水中，最终被漩涡捕获。
The Arctic Ocean is known to be quiescent in terms of turbulent kinetic energy (TKE) associated with internal waves. To investigate the current state of TKE in the seasonally ice-free Chukchi Plateau, Arctic Ocean, this study performed a 3-week, fixed-point observation (FPO) using repeated microstructure, hydrographic, and current measurements in September 2014. During the FPO program, the microstructure observation detected noticeable peaks of TKE dissipation rate epsilon during the transect of an anticyclonic eddy moving across the FPO station. Particularly, epsilon had a significant elevation in the lower halocline layer, near the critical level, reaching the order of 10 28 Wkg 21. The ADCP-measured current displayed energetic near-inertial internal waves (NIWs) propagating via the stratification at the top and bottom of the anticyclone. According to spectral analyses of horizontal velocity, the waves had almost downward energy propagation, and its current amplitude reached similar to 10 cm s(-1). The WKB scaling, incorporating vertical variations of relative vorticity, suggests that increased wave energy near the two pycnoclines was associated with diminishing group velocity at the corresponding depths. The finescale parameterization using observed near-inertial velocity and buoyancy frequency successfully reproduced the characteristics of observed epsilon, supporting that the near-inertial kinetic energy can be effectively dissipated into turbulence near the critical layer. According to a mixed layer slab model, a rapidly moving storm that has passed over in the first week likely delivered the bulk of NIW kinetic energy, eventually captured by the vortex, into the surface water.