Roles of Shear and Convection in Driving Mixing in the Ocean

Gregory Ivey, Cynthia E. Bluteau, Bishakhdatta Gayen, Nicole Jones, Taimoor Sohail

Research output: Contribution to journalLetter

Abstract

Using field, numerical, and laboratory studies, we consider the roles of both shear and convection in driving mixing in the interior of the density‐stratified ocean. Shear mixing dominates when the Richardson number Ri < 0.25, convective mixing dominates when Ri > 1.0, and in the intermediate regime when 0.25 < Ri < 1.0 both shear and convection can contribute to mixing. For pure shear mixing the mixing efficiency Rif approaches 0.5, while for pure convective mixing the mixing efficiency Rif approaches 0.75. The diapycnal diffusivities for the two mechanisms are given by very different expressions. Despite these complexities, a simple mixing length model using the mean flow shear S provides robust estimates of diffusivity across the range 0 < Ri < 2. To account for the roles of both shear and convection over this range of Ri, we also formulate a modified version of the empirical KPP model for parameterizing ocean mixing in numerical models.
Original languageEnglish
Article numbere2020GL089455
JournalGeophysical Research Letters
Volume48
Issue number3
DOIs
Publication statusPublished - 16 Feb 2021

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