Document Type
Article
Publication Date
2008
DOI
10.1007/s10652-008-9107-2
Publication Title
Environmental Fluid Mechanics
Volume
8
Issue
5-6
Pages
495-509
Abstract
Estuarine turbulence is notable in that both the dissipation rate and the buoyancy frequency extend to much higher values than in other natural environments. The high dissipation rates lead to a distinct inertial subrange in the velocity and scalar spectra, which can be exploited for quantifying the turbulence quantities. However, high buoyancy frequencies lead to small Ozmidov scales, which require high sampling rates and small spatial aperture to resolve the turbulent fluxes. A set of observations in a highly stratified estuary demonstrate the effectiveness of a vessel-mounted turbulence array for resolving turbulent processes, and for relating the turbulence to the forcing by the Reynolds-averaged flow. The observations focus on the ebb, when most of the buoyancy flux occurs. Three stages of mixing are observed: (1) intermittent and localized but intense shear instability during the early ebb; (2) continuous and relatively homogeneous shear-induced mixing during the mid-ebb, and weakly stratified, boundary-layer mixing during the late ebb. The mixing efficiency as quantified by the flux Richardson number Rf was frequently observed to be higher than the canonical value of 0.15 from Osborn (J Phys Oceanogr 10:83-89, 1980). The high efficiency may be linked to the temporal-spatial evolution of shear instabilities.
Rights
This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
Original Publication Citation
Geyer, W., Scully, M., & Ralston, D. (2008). Quantifying vertical mixing in estuaries. Environmental Fluid Mechanics, 8(5-6), 495-509. doi:10.1007/s10652-008-9107-2
Repository Citation
Geyer, W. Rockwell; Scully, Malcolm E.; and Ralston, David K., "Quantifying Vertical Mixing in Estuaries" (2008). CCPO Publications. 242.
https://digitalcommons.odu.edu/ccpo_pubs/242
Included in
Environmental Sciences Commons, Fluid Dynamics Commons, Geophysics and Seismology Commons, Oceanography Commons