spatial distribution of diapycnal mixing rates in the deep waters of the North Pacific

北太平洋深水区二重混合率的空间分布

基本信息

批准号：
12440125
负责人：
HIBIYA Toshiyuki
金额：
$ 9.66万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440125/
关键词：
diapycnal mixing North Pacific global abyssal circulation internal tides inertial frequency energy cascade nonlinear interactions parametric subbarmonic instability 深層 Parametric subharmonic instability 中緯度低気圧 3波共鳴干渉機構 XCP XCTD観測

项目摘要

The mechanical energy which drives the interior mixing in the oceans is believed to be originally supplied at large scales and then transferred across the deep ocean internal wave spectrum down to small dissipation scales. In recent numerical experiments (Hibiya et al., 1996, 1998, 2002), this energy cascade process was shown to be dominated by parametric subharmonic instabilities which transfer energy from the low vertical wavenumber, double-inertial frequency wave band to a high vertical wavenumber, near-inertial frequency wave band. The resulting enhanced, high vertical wavenumber, nearinertial current shear was shown to play a key role in controlling turbulent mixing processes.In this study, to test whether or not the numerically predicted energy cascade process is actually dominant in the real deep we deployed a total of 106 expendable current profilers over a large area in the North Pacific to examine the spatial distribution of high vertical wavenumber (vertical wavelength 〜25 m … More ) shear. At mid latitudes, significant enhancement of the 25-m vertical shear was found over prominent generation regions of semidiurnal internal tides such as the Hawaiian Ridge and the Izu-Ogasawara Ridge where the semidiurnal tidal frequency exceeds twice the local inertial frequency. At high latitudes, in contrast, no significant enhancement of the 25-m vertical shear was found to occur even over another prominent generation region of semidiurnal internaUtides, the Aleutian Ridge, where the semidiurnal tidal frequency is less than twice the local inertial frequency. We find that the observed spatial distribution of the intensity of the 25-m vertical shear correlates very well with that of the low vertical wavenumber, double-inertial frequency internal wave energy numerically predicted by Nagasawa et al. [2000] and Niwa and Hibiya [2001]. This is the first in-situ evidence for the dominant role of parametric subharmonic instability in transferring deep ocean internal wave energy down to small dissipation scales. This study provides a theoretical framework for future attempts to determine the large-scale structure of mixing over the world's oceans. Less

据信，驱动海洋内部混合的机械能最初是在大尺度上提供的，然后在深海内波光谱上转移至小耗散量表。在最近的数值实验（Hibiya等，1996，1998，2002）中，该能量级联进程被证明是由参数亚谐波不稳定性主导的，这些能量从低垂直波形，双惯性波段的低垂直垂直波段转移到高垂直波形到高垂直波伯伯，接近直直直直直鼻频率波带。结果显示，结果增强，高垂直波数，近端电流剪切在控制湍流混合过程中起着关键作用。在这项研究中，为了测试数值预测的能量级联进程是否在实际深层中占主导地位剪。在纬度中间，发现半潮湿的内部潮汐（如夏威夷山脊和izu-ogasawara Ridge）的著名产生区域的25米垂直剪切的显着增强，半潮汐潮汐频率超过了局部惯性频率的两倍。相比之下，在高纬度时，即使在半潮湿的内部尿道的另一个突出的产生区域Aleutian Ridge，半潮湿的潮汐频率是局部惯性频率的两倍。我们发现，观察到的25 m垂直剪切强度的空间分布与Nagasawa等人在数值上预测的低垂直波数的低垂直波数频率内波能的空间分布非常相关。 [2000]以及Niwa和Hibiya [2001]。这是参数亚谐波不稳定性在将深海内波能量转移到小耗散量表中的主要作用的原位证据。这项研究提供了一个理论框架，用于未来尝试确定世界海洋混合的大规模结构。较少的