The rate of turbulent kinetic energy dissipation and diapycnal diffusivity are estimated along 10 hydrographic sections across the Indian Ocean from a depth of 500 m to the seabed. Six sections were occupied twice. On the meridional section, which is nominally along 95°E, spatial patterns were observed to persist throughout the three occupations. Since the variability in diffusivity exceeds the variability in the vertical gradients of temperature and salinity, we conclude that the diffusive diapycnal fluxes vary mostly with diffusivity. In high latitudes, diapycnal diffusions of both temperature and salinity contribute almost equally to density diffusion, particularly across isopycnals just above the salinity maximum, while mainly temperature contributes in other latitudes. The known zonal difference in turbulence is reproduced. Diffusivity from the seabed to 4,000 m above the seabed has an exponential profile with a mode value of 4 × 10⁻⁴ m²s⁻¹ at 1,000 m above the seabed and is positively correlated with topographic roughness as reported previously. It is found that the diffusivity also correlates with wind power injected through the surface at near-inertial frequencies 10–80 days before the observations. These correlations were used to interpolate the observation-based turbulence quantities to the entire Indian Ocean. Although the dissipation averaged along selected neutral-density surfaces is less than the dissipation needed to explain the meridional overturning circulation evaluated across 32°S latitude, this may be explained by effects not captured by the ship-based observations and parameterization. These effects likely include unobserved high-mixing events, near bottom processes (e.g., hydraulic jumps), and deep equatorial jets.

中文翻译：

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印度洋环相混合的时空变异性

沿着印度洋从 500 m 深度到海床的 10 个水文断面估计了湍流动能耗散率和透心扩散率。六个部分被占用了两次。在名义上沿 95°E 的子午线部分，观察到空间模式在三个职业中持续存在。由于扩散率的变异性超过了温度和盐度垂直梯度的变异性，我们得出结论，扩散的渗流通量主要随扩散率而变化。在高纬度地区，温度和盐度的双密度扩散对密度扩散的贡献几乎相等，特别是在盐度最大值以上的等密度线上，而在其他纬度主要是温度贡献。再现了已知的湍流纬向差异。⁻⁴ m ² s ⁻¹在海床上方 1,000 m 处，并且与先前报道的地形粗糙度呈正相关。发现扩散率还与观测前 10-80 天以近惯性频率通过地表注入的风能相关。这些相关性用于将基于观测的湍流量内插到整个印度洋。尽管沿选定的中性密度表面平均的耗散小于解释跨 32°S 纬度评估的经向翻转环流所需的耗散，但这可能是由舰载观测和参数化未捕获的影响来解释的。这些影响可能包括未观察到的高混合事件、近底过程（例如，水跃）和深赤道急流。