Direct measurement of near-bottom turbulence in deep ocean for predicting behavior of suspended particles in Sagami Bay and the Okinawa Trough, Japan
Direct measurement of near-bottom turbulence in deep ocean for predicting behavior of suspended particles in Sagami Bay and the Okinawa Trough, Japan
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发表时间：
2017-09
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通讯作者：
Y. Furushima;H. Higashi;T. Fukuhara;N. Furuichi;Hiroyuki Yamamoto
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作者：
Y. Furushima;H. Higashi;T. Fukuhara;N. Furuichi;Hiroyuki Yamamoto
在这项研究中，湍流测量使用一次性垂直微结构剖面仪（VMP-X）在热液领域的冲绳海槽（Iheya北场和Noho网站）和相模湾（关闭伊藤和Ohmuro火山口）的湍流强度的特征。对于每个观测点，成功地测量了海面和海底之间的湍流数据。在伊藤港附近的海底，测得的能量耗散率（ε）为10−6（W kg−1）。该值与在表面混合层中经常观察到的值相当。实时海流测量值是由日本海洋科学技术研究所运营的、位于Hatsushima岛外的实时深海海底观测站的声学多普勒海流剖面仪获得的。ADCP资料证实了湍流测量时的强东北流。这种强烈的东北气流可能会加剧海底附近的湍流。重要的是，我们以这种方式澄清湍流数据和现有数据的响应。在冲绳海槽中直接测量湍流的结果是，底部附近的湍流能量耗散率（ε）约为10−7（W kg−1）。从底部到距底部约20 m的高度，湍流很强，冲绳海槽Noho站点的水温略有上升。这种波动可能是由于热液喷发的影响。因此，湍流强度（ε：能量耗散率）也可能受到热液喷发的影响。然而，使用湍流流量计（VMP-X）获得的结果只是一个快照，需要更多的现场观测数据来了解底部混合层（湍流）的动态。因此，考虑到时空动态的数据归档仍然是必要的。
In this study, turbulent flows were measured using the Expendable Vertical Microstructure Profiler (VMP-X) at the hydrothermal fields in the Okinawa Trough (Iheya North field and Noho site) and Sagami Bay (off Itoh and at Ohmuro Caldera) to characterize the turbulence intensity. For each observation point, the turbulent flow data were successfully measured between the sea surface and the sea floor. In the vicinity of the sea floor off Itoh port, the energy dissipation rate (ε) was measured as 10−6 (W kg−1). This value was equivalent to that frequently observed in the surface mixed layer. Real-time current measurements are obtained from the Acoustic Doppler Current Profiler (ADCP) at the Real-time Deep Seafloor Observatory off Hatsushima Island, which is operated by JAMSTEC. Strong northeastward flows at the time of turbulent flow measurement were confirmed by ADCP data. Such strong northeastward flows may intensify turbulence near the sea floor. It is important that we clarify the response with turbulent flow data and existing data in this way. As a result of the direct measurement of turbulent flow in the Okinawa Trough, the turbulent energy dissipation rate (ε) near the bottom was approximately 10−7 (W kg−1). Turbulent flow was strong from the bottom to a height of around 20 m from the bottom, and water temperature slightly rose at the Noho site in the Okinawa Trough. This fluctuation may be due to the influence of hydrothermal venting. Therefore, the intensity of turbulence (ε: energy dissipation rate) may also be affected by the hydrothermal venting. However, the results obtained using the turbulent flow meter (VMP-X) are only a snapshot, and more in-situ observational data is necessary to understand the dynamics of the bottom mixed layer (turbulent flow). Therefore, data filing in consideration of spatiotemporal dynamics is still necessary.