Squeeze Dispersion and the Effective Diapycnal Diffusivity of Oceanic Tracers

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.

• Publication year

  2019

• Venue

  Geophysical Research Letters

• Publication date

  2019-05-21

• Fields of study

  Geology, Physics, Environmental Science

• Identifiers
  DOI 10.1029/2019GL082458
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar

• No claims are published for this paper.

• No concepts are published for this paper.

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