Squeeze Dispersion and the Effective Diapycnal Diffusivity of Oceanic Tracers
Squeeze Dispersion and the Effective Diapycnal Diffusivity of Oceanic Tracers
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DOI：
10.1029/2019gl082458
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发表时间：
2019-05
影响因子：
5.2
通讯作者：
G. Wagner;G. Flierl;R. Ferrari;Gunnar Voet;G. Carter;M. Alford;J. Girton
中科院分区：
文献类型：
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作者：
G. Wagner;G. Flierl;R. Ferrari;Gunnar Voet;G. Carter;M. Alford;J. Girton
我们描述了一个被称为“挤压扩散”的过程，在这个过程中，波浪、漩涡和测深流对海洋示踪剂梯度的挤压通过厘米到米尺度的湍流来调节透膜扩散。由于挤压分散，海洋示踪剂的有效diapycnal扩散率是不同的，通常大于平均的“本地”扩散率，特别是当本地扩散率与挤压。我们发展了一个理论来量化挤压弥散对纵摇海洋输运的影响，找到了连接密度平均示踪剂通量、局部测量扩散率、大尺度海洋应变、厚度加权平均浮力梯度和海洋示踪剂有效扩散率的公式。我们使用这种有效扩散率来解释阿尔福德等人（2013年，https：//doi.org/10.1002/grl.50684）报告的通过萨摩亚海峡的深海水流的观察结果，并发现挤压对环膜示踪剂分散的调节系数在0.5到3之间。
We describe a process called “squeeze dispersion” in which the squeezing of oceanic tracer gradients by waves, eddies, and bathymetric flow modulates diapycnal diffusion by centimeter to meter‐scale turbulence. Due to squeeze dispersion, the effective diapycnal diffusivity of oceanic tracers is different and typically greater than the average “local” diffusivity, especially when local diffusivity correlates with squeezing. We develop a theory to quantify the effects of squeeze dispersion on diapycnal oceanic transport, finding formulas that connect density‐averaged tracer flux, locally measured diffusivity, large‐scale oceanic strain, the thickness‐weighted average buoyancy gradient, and the effective diffusivity of oceanic tracers. We use this effective diffusivity to interpret observations of abyssal flow through the Samoan Passage reported by Alford et al. (2013, https://doi.org/10.1002/grl.50684) and find that squeezing modulates diapycnal tracer dispersion by factors between 0.5 and 3.