Volume 25, Issue 15 p. 2761-2764
Free Access

Secondary circulation associated with a shelfbreak front

John A. Barth

John A. Barth

College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis, Oregon

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Darek Bogucki

Darek Bogucki

College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis, Oregon

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Stephen D. Pierce

Stephen D. Pierce

College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis, Oregon

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P. Michael Kosro

P. Michael Kosro

College of Oceanic & Atmospheric Sciences, Oregon State University, Corvallis, Oregon

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First published: 01 August 1998
Citations: 62

Abstract

Evidence for secondary circulation associated with a shelfbreak front is obtained from a high-resolution, cross-shelf section of hydrographic, optical and velocity fields. Convergence in the bottom boundary layer on the inshore side of the front and subsequent upwelling into the interior is evident by a mid-water region of suspended bottom material emanating from the foot of the front and extending to within 35 m of the surface, 80 m above bottom. Downwelling on the offshore side of the front in the upper water column is inferred from a 20-m downward bend of the subsurface phytoplankton layer. These observations are in agreement with recent model predictions for secondary circulation near an idealized shelfbreak front. Convergence in measured cross-shelf velocity at the foot of the front is consistent with upwelling of bottom material detected there. An estimate of 9±2 m day−1 of upwelling on the inshore side of the shelfbreak front is obtained, implying a transit time from the bottom to the surface of 10–16 days.