Observed variations in turbulent mixing efficiency in the deep ocean
MetadataShow full item record
KeywordAbyssal circulation; Mixing; Subgrid-scale processes; Turbulence; In situ oceanic observations
Recent progress in direct numerical simulations (DNSs) of stratified turbulent flows has led to increasing attention to the validity of the constancy of the dissipation flux coefficient Γ in the Osborn’s eddy diffusivity model. Motivated by lack of observational estimates of Γ, particularly under weakly stratified deep-ocean conditions, this study estimates Γ using deep microstructure profiles collected in various regions of the North Pacific and Southern Oceans. It is shown that Γ is not constant but varies significantly with the Ozmidov/Thorpe scale ratio ROT in a fashion similar to that obtained by previous DNS studies. Efficient mixing events with Γ ~ O(1) and ROT ~ O(0.1) tend to be frequently observed in the deep ocean (i.e., weak stratification), while moderate mixing events with Γ ~ O(0.1) and ROT ~ O(1) tend to be observed in the upper ocean (i.e., strong stratification). The observed negative relationship between Γ and ROT is consistent with a simple scaling that can be derived from classical turbulence theories. In contrast, the observed results exhibit no definite relationships between Γ and the buoyancy Reynolds number Reb, although Reb has long been thought to be another key parameter that controls Γ.
Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 48 (2018): 1815-1830, doi:10.1175/JPO-D-17-0275.1.
Suggested CitationJournal of Physical Oceanography 48 (2018): 1815-1830
Showing items related by title, author, creator and subject.
Fu, Lee-Lueng (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1980-02)The structure of the inertial peak in deep ocean kinetic energy spectra is studied here. Records were obtained from Polymode arrays deployed in the Western North Atlantic Ocean (40°W to 70°W, 15°N to 42°N). The results ...
Rainville, Luc; Winsor, Peter (American Geophysical Union, 2008-04-30)Turbulent-scale temperature and conductivity were measured during the pan-arctic Beringia 2005 Expedition. The rates of dissipation of thermal variance and diapycnal diffusivities are calculated along a section from Alaska ...
Gerbi, Gregory P.; Trowbridge, John H.; Terray, Eugene A.; Plueddemann, Albert J.; Kukulka, Tobias (American Meteorological Society, 2009-05)Observations of turbulent kinetic energy (TKE) dynamics in the ocean surface boundary layer are presented here and compared with results from previous observational, numerical, and analytic studies. As in previous studies, ...