Premium
Roles of Shear and Convection in Driving Mixing in the Ocean
Author(s) -
Ivey Gregory N.,
Bluteau Cynthia E.,
Gayen Bishakhdatta,
Jones Nicole L.,
Sohail Taimoor
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl089455
Subject(s) - convection , mixing (physics) , convective mixing , richardson number , shear (geology) , thermal diffusivity , mechanics , geology , shear flow , meteorology , physics , thermodynamics , turbulence , petrology , quantum mechanics
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 Ri f approaches 0.5, while for pure convective mixing the mixing efficiency Ri f 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.