Laboratory Modelling of the Dynamics of Coastal Upwelling
Rept. for 1 Sep 1987-28 Feb 1991
CALIFORNIA UNIV LOS ANGELES
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The aim of this research was to study and understand the dynamics of the filamentary structures that have been repeatedly observed by satellite IR images taken from the West Coast of the USA, during coastal upwelling episodes. We have simulated such episodes in our laboratory model and generated coastal upwelling fronts and associated jets and eddies. When the experimental model was free of coastal irregularities capes, ridges, canyons, etc., the upwelled front was uniform and a train of cyclonic-anticyclonic eddies were formed. Under some circumstances, many of these eddies pinched off and moved offshore into the fluid interior. We investigated the structure of such an eddy system and show that its structure falls within the category of two-dimensional andor geostrophic turbulence. This in turn suggests that the eddy field contains many turbulent jets or rivers that are responsible for the transport of the passive material and cold, upwelled fluid across the eddy field. To demonstrate this, we released a passive marker near the front and noted that it was immediately transported offshore by the turbulent jets, and filamentary structures, similar to those seen in the satellite images, have evolved. When coastal irregularities were included into the system many more eddies were generated and injected into the eddy system.
- Physical and Dynamic Oceanography
- Fluid Mechanics