The effect of submarine canyon width and stratification on coastal circulation and across shelf exchange

A 3-D ocean circulation model is used to investigate the effect of the width of a submarine canyon and stratification on adjacent coastal circulation and across shelf exchange. Upwelling winds for 20 d drive circulation over six canyons of varying widths (8--60 km), two escarpments to represent infinitely wide canyons, and a generic shelf-slope without a canyon. Also six stratifications whose first internal Rossby radii (a) range over 2--18 km were applied to two canyons (20 and 40 km) to see the effect of stratification. All simulations adjust to the canyon after 5 days spinup and reach an approximate steady state after two weeks. Cyclonic circulation, continuous onshore transport and upwelling occur within the canyons. All canyons can be classified as narrow, intermediate or wide by the ratio of the internal deformation radius to the canyon width. A canyon with a width of about 2a, which is the size of cyclone over wide canyon, separates wide from narrow canyons. Alongshore transport upstream of canyon and onshore transport within the canyon has a relationship of power function which has different parameters before and after the adjustment. The geometric effect of a narrow canyon is very strong based on the onshore transport per unit width and tracer moving speed within the canyon, even though wider canyons have larger onshore transport. Canyon drag decreases as the canyon narrows and stratification increases, which produces large alongshore transport for strong stratification and large onshore transport for weak stratification.