Spatial and Temporal Variability of Diapycnal Mixing in the Indian Ocean
Spatial and Temporal Variability of Diapycnal Mixing in the Indian Ocean
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DOI：
10.1029/2021jc017257
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发表时间：
2021-07
期刊：
影响因子：
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通讯作者：
K. Katsumata;L. Talley;T. A. Capuano;C. Whalen
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文献类型：
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作者：
K. Katsumata;L. Talley;T. A. Capuano;C. Whalen
估计了沿印度洋从500米到海床深度的10个水文断面的湍流动能耗散率和昼夜扩散率。六个路段被占领了两次。在名义上沿95°E的子午线上，观察到空间格局贯穿于这三个职业。由于扩散系数的变异性大于温度和盐度垂直梯度的变异性，因此我们得出结论：扩散通量主要随扩散系数而变化。在高纬度地区，温度和盐度的昼夜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径线上，而在其他纬度主要是温度贡献。再现了湍流中已知的纬向差异。从海床到海床以上4,000米处的扩散系数具有指数分布，在海床以上1,000米处的模式值为4×10−4m2s−1，并与先前报告的地形粗糙度呈正相关。结果发现，扩散系数还与观测前10-80天通过地面注入的近惯性频率的风能相关。这些相关性被用来将基于观测的湍流量内插到整个印度洋。虽然沿着选定的中性密度面平均的耗散小于解释经向翻转环流所需的耗散，但这可能是由于船基观测和参数化未能捕捉到的影响。这些影响可能包括未观测到的高混合事件、近底过程(例如，水力跳跃)和深赤道急流。
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 × 10−4m2s−1at 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.