Global mapping of diapycnal mixing rates in the deep ocean

全球温跃层底跃层混合率的测绘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。为此目的，我们首先将一次性海流剖面仪（XCP）测量的水平速度的细尺度垂直切变纳入Gregg公式（Gregg，1989），估算了北太平洋、南太平洋、北大西洋和南印度洋内部大面积的纵摇混合率。XCP测量的显著发现是，温跃层中的底回旋混合率的估计值与纬度有很强的相关性，然后将这些估计值与底回旋混合的主要能量源、数值计算的各位置的半月内潮能量联系起来，找到了一个预测深海底回旋混合率全球分布的经验公式。将数值预报的各经纬度半日内潮能量代入经验公式，我们发现，强的横隔混合（混合热点）仅限于纬度20^0 - 30^1的突出地形特征。其中可用的半日内潮能量可以通过内波之间的共振相互作用（称为参数次谐波）有效地转移到耗散尺度将所获得的底界混合率分布嵌入全球温盐环流模式，应能大大提高其预测未来气候变化的能力。

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.