Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6388721 | Progress in Oceanography | 2013 | 12 Pages |
Abstract
The role played by inertial motions in horizontal dispersion within the thermocline of a broad, mid-latitude shelf sea is examined through the analysis of a deliberately released dye tracer. Our analysis is of the horizontal and vertical evolution over 40Â h of a dye tracer injected into the seasonally stratified thermocline of the Celtic Sea on the NW European Shelf. The inferred diapycnal diffusivity was 1.3-1.5Â ÃÂ 10â5Â m2Â sâ1, and the radial horizontal diffusivities of the depth integrated dye patch ranged from 1.9 to 4.0Â m2Â sâ1. The inferred vertical diffusivity is in agreement with microstructure based estimates, and the depth integrated horizontal diffusivity is broadly in agreement with previous dye release derived estimates made over similar scales and time periods. Asymmetry in the horizontal evolution of the dye patch was evident. We argue that mean shear dispersion was responsible for lateral elongation of the dye patch, particularly between hours 23 and 35 after release, during which time horizontal diffusivity along the major axis, Ka, exceeded that along the minor axis, Kb, by more than a factor of 10. We further show that along-patch shear was predominantly a result of differential advection between a deep residual flow to the south-east and an oscillating wind-driven surface Ekman layer. In this region of strong low frequency (inertial) shear a time dependent model of shear dispersion (Young et al., 1982) was able to account for the observed rate of horizontal dispersion calculated on the target isopycnal surface.
Related Topics
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Authors
Mark E. Inall, Dmitry Aleynik, Clare Neil,