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

机械能驱动海洋被认为是在最近的数值体验中向小耗散量表的海洋内波谱。通过参数谐波的不稳定性，将能量从lownucal ber，双惯性频带带到高垂直波数，近惯性频率波带。预测的能量级联进程实际上是真正的深处，我们在北太平洋大面积的大面积上总共部署了106个消耗的电流伪造者，以检查高垂直波数漆的空间分布，发现了25 m的垂直剪切层的显着增强在夏威夷山脊和izu-ogasawara山脊等半职纳尔纳尔杂交的突出中，ticeeds两次是局部惯性频率的两倍。半潮间的内部，阿留申山脊，然后降低了两倍的惯性频率。将深海内波能量转移到小型耗散量表时，谐波不稳定