Squeeze dispersion and the effective diapycnal diffusivity of oceanic tracers
Name
Wagneretal18.pdf
Description
Accepted version
Size
6.61 MB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Wagner, Gregory L.
Flierl, Glenn Richard
Ferrari, Raffaele
Date Issued
April 2019
Journal
Geophysical Research Letters
Publisher
American Geophysical Union (AGU)
Citation
Wagner, Gregory L. et al. “Squeeze dispersion and the effective diapycnal diffusivity of oceanic tracers.” Geophysical Research Letters, 46, 5 (April 2019) © 2019 The Author(s)
Version
Author's final manuscript
Abstract
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.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1029/2019GL082458
