Mixing at the head of a canyon : a laboratory investigation of fluid exchanges in a rotating, stratified basin
MetadataShow full item record
Observations indicate that oceanic mixing is intensified near the head of submarine canyons. How the presence of canyon walls affects the local production and distribution of mixed fluid is an open question. These dynamics are addressed through rotating tank experiments which impose mixing at middepth at the closed end of a channel open to a larger body of water. Turbulence is generated in a linearly stratified fluid with initial buoyancy frequency N by means of a single bar oscillated with frequency ω. The mixed fluid quickly reaches a steady state height h ∼ (ω/N)1/2 independent of the Coriolis frequency f and collapses into the channel interior. A small percentage of the fluid exported from the turbulent zone enters a boundary current. The bulk forms a cyclonic circulation in front of the bar. As the recirculation cell expands to fill the channel, it restricts horizontal entrainment into the turbulent zone. Mixed fluid flux decays with time as t inline equation and is dependent on the size of the mixing zone and the balance between turbulence, rotation, and stratification. The recirculation cell is confined within the channel, and export of mixed fluid into the basin is restricted to the weak boundary current. As horizontal entrainment is shut down, long-term production of mixed fluid relies more on vertical entrainment. However, the scalings indicate that short-term dynamics are the most applicable to oceanic conditions.
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C12004, doi:10.1029/2006JC003667.
Showing items related by title, author, creator and subject.
Laboratory observations of enhanced entrainment in dense overflows in the presence of submarine canyons and ridges Wåhlin, A. K.; Darelius, Elin; Cenedese, Claudia; Lane-Serff, G. F. (2008-01-29)The continental slopes in the oceans are often covered by small-scale topographic features such as submarine canyons and ridges. When dense plumes, flowing geostrophically along the slope, encounter such features they ...
Laboratory experiments on the interaction of a buoyant coastal current with a canyon : application to the East Greenland Current Sutherland, David A.; Cenedese, Claudia (American Meteorological Society, 2009-05)This paper presents a set of laboratory experiments focused on how a buoyant coastal current flowing over a sloping bottom interacts with a canyon and what controls the separation, if any, of the current from the upstream ...
Dell, Rebecca Walsh (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-06)This paper begins to explore a previously neglected mechanism for abyssal ocean mixing using bottom boundary layer dynamics. Abyssal mixing and the associated upward buoyancy fluxes are necessary to balance the sinking ...