Collaborative Research: Dye Tracer and Modeling Investigations of Cross-Shelf Circulation during Coastal Upwelling

Oregon State University, Corvallis OR

Investigators

Abstract

Dale 0136900 Field and simulation studies will be used to determine where upwelled water originates, i.e. solely from the bottom boundary layer (BBL) or from a thicker region of the lower layer fluid, and where the displaced surface water goes, e.g. offshore in the the surface layer or, through subduction, to intermediate layers. Five dye studies, using fluorescene and rhodamine-WT, are proposed for the upwelling region over the Oregon shelf. Releases will occur in three different locations - beneath and inshore of the upwelling jet, in the BBL beneath the jet where onshore movement is expected, and inshore of the jet, just beneath the mixed layer but still in the Ekman layer, where offshore movement and possible subduction is expected. Dye will be tracked for 72 hours. The background environment will be defined by GLOBEC cruises, at least during the first field year. Three releases from the R/V Elakha will be traced during the first year. The second year will involve two larger releases from the R/V Wecoma. A version of the Princeton Ocean Model, configured for the region, will be run for comparison. Particle tracing techniques will be used to model the initial, small-scale dispersion. Both idealized situations and realistic modeling will be attempted. A 2-D ocean-going model will be used, in conjunction with buoyed GPS drifters, to track the subsurface dye patch after release. The results of the study will be a set of Lagrangian observations of cross-shelf transport pathways during upwelling. These will lead to improved understanding of circulation and mixing.