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Global mapping of diapycnal mixing rates in the deep ocean

深海二重混合率的全球测绘

基本信息

批准号：
14340136
负责人：
HIBIYA Toshiyuki
金额：
$ 10.82万
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：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340136/
关键词：
Diapycnal mixing Latitudinal dependence Global thermohaline circulation model Semidiurnal internal tides Parametric subharmonic instability Energy cascade Near inertial current shear Expendable current profiler 投棄式流速計乱流拡散海洋深層流速シアー

项目摘要

Global mapping of diapycnal mixing rates in the thermocline is essential to improve the ability of global thermohaline circulation models in predicting future climate changes. For this purpose, we have first estimated diapycnal mixing rates over a large area in the interior of the North and South Pacific, the North Atlantic and the South Indian Ocean by incorporating the fine-scale vertical shear of horizontal velocity measured by expendable current profilers (XCP) into Gregg's formula (Gregg, 1989). The remarkable finding from the XCP survey is that the estimated diapycnal mixing rate in the thermocline is strongly dependent on the latitude.Then, these estimates have been related to the main energy source for diapycnal mixing, the semidiumal internal tide energy numerically calculated at each location, and an empirical formula has been found to predict the global distribution of diapycnal mixing rates in the deep ocean. Incorporating the numerically predicted semidiurnal internal tide energy at each longitude and latitude into the resulting empirical formula, we have found that strong diapycnal mixing (mixing hotspot) is limited to prominent topographic features at latitudes 20^0 -30^0 where the available semidiurnal internal tide energy can be efficiently transferred to dissipation scales by resonant interactions amongst internal waves called parametric subharmonic instability.Embedding the obtained distribution of diapycnal mixing rates into global thermohaline circulation models should yield significant improvement in their ability to predict future climate change.

全球测绘温跃层中的昼夜混合率对于提高全球温盐环流模式预测未来气候变化的能力至关重要。为此，我们首先通过将可消耗性海流剖面仪(XCP)测量的水平速度的细尺度垂直切变纳入Gregg公式(Gregg，1989)，估计了北太平洋、南太平洋、北大西洋和南印度洋大范围的昼夜混合率。XCP调查的一个显著发现是，温跃层中估计的昼夜混合率强烈依赖于纬度。然后，这些估计值与昼夜混合的主要能量来源--在每个位置数值计算的半日内潮汐能量--相关联，并找到了一个预测深海昼夜混合率全球分布的经验公式。将数值预测的各经度和纬度的半日内潮汐能量结合到所得到的经验公式中，我们发现，强日潮混合(混合热点)仅限于纬度20^0-30^0的显著地形特征，在那里，可利用的半日内潮汐能量可以通过内波之间的共振相互作用有效地转移到耗散尺度上，称为参数亚谐不稳定。将所获得的日混合率分布嵌入全球温盐环流模式中，应该会显著提高它们预测未来气候变化的能力。