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.

温跃层中二重混合率的全球绘图对于提高全球温盐环流模型预测未来气候变化的能力至关重要。为此，我们首先通过结合消耗性海流剖面仪测量的水平速度的细尺度垂直切变来估计北太平洋、南太平洋、北大西洋和南印度洋内部大面积的二重混合率（ XCP）代入 Gregg 公式（Gregg，1989）。 XCP调查的显着发现是，估计的温跃层中的二重混合速率强烈依赖于纬度。然后，这些估计与二重混合的主要能量来源有关，即在每个位置数值计算的半内潮汐能，并且已经找到了一个经验公式来预测深海中二重混合率的全球分布。将数值预测的各经度和纬度的半日内潮能量纳入所得的经验公式中，我们发现强二重混合（混合热点）仅限于纬度 20^0 -30^0 处的显着地形特征，其中可用的半日内潮能量潮汐能可以通过内波之间的共振相互作用（称为参数次谐波不稳定性）有效地转移到耗散尺度。将获得的二重混合率分布嵌入到全局中温盐环流模型应该能够显着提高预测未来气候变化的能力。