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Shelf-slope exchanges associated with a steep submarine canyon off Calvi (Corsica, NW Mediterranean Sea): A modeling approach

Shelf-slope exchanges associated with a steep submarine canyon off Calvi (Corsica, NW Mediterranean Sea): A modeling approach
Shelf-slope exchanges associated with a steep submarine canyon off Calvi (Corsica, NW Mediterranean Sea): A modeling approach
A three-dimensional, unsteady, nonlinear, high-resolution model is used to investigate the impact of the Calvi Canyon (NW Corsica) steep topography on the shelf-slope exchanges as well as on the circulation in the Calvi Bay in homogeneous winter and early spring conditions. A double ? coordinate system is considered in order to represent adequately the high depth gradients within the canyon. The studied region is under the influence of the West Corsica Current flowing northeastward along the NW Corsican coast (right-bounded flow). Model results show that the circulation in the Calvi Bay is determined by flow modifications in the canyon area. The mean horizontal flow is deviated southwestward upstream of the canyon to form an anticyclonic gyre in the western part of the Calvi Bay. Within the canyon the circulation is cyclonic leading to an offshore flow downstream of the canyon. Around the canyon rim, the cross-shelf currents become important, indicating that this region acts as a transition zone of high exchange between nearshore and offshore areas. Furthermore, the canyon topography generates high downwelling (upwelling) and downsloping (upsloping) velocities responsible for an intense vertical transport of material in the area. Numerical runs are performed for typical prevailing wind conditions. The wind is responsible for a drastic increase of cross-shore transports between the bay and the canyon area (3–4 times larger than in the no-wind case). SW winds induce a further enhancement of cross-shelf exchanges, whereas the effect of N-NE winds is to reduce exchange at the shelf break apart from the canyon head where an intense offshore flow occurs. Within the canyon, high vertical velocities are shown to be associated with high cyclonic vorticity which is enhanced (reduced) by the N-NE (SW) wind event. A comparison between model results and measured distributions of nitrate and chlorophyll a concentrations in the area shows the role played by this specific hydrodynamics as a strong constraint on the coastal pelagic ecosystem.
0148-0227
19883-19901
Skliris, N.
07af7484-2e14-49aa-9cd3-1979ea9b064e
Goffart, A.
35c08b9c-5376-4173-bccf-d77d279f3d45
Hecq, J.H.
089d8ea1-eb46-4102-b33a-6b6a28c81df8
Djenidi, S.
0c0f008b-5712-4d8e-aa58-d10ccf3a57b1
Skliris, N.
07af7484-2e14-49aa-9cd3-1979ea9b064e
Goffart, A.
35c08b9c-5376-4173-bccf-d77d279f3d45
Hecq, J.H.
089d8ea1-eb46-4102-b33a-6b6a28c81df8
Djenidi, S.
0c0f008b-5712-4d8e-aa58-d10ccf3a57b1

Skliris, N., Goffart, A., Hecq, J.H. and Djenidi, S. (2001) Shelf-slope exchanges associated with a steep submarine canyon off Calvi (Corsica, NW Mediterranean Sea): A modeling approach. Journal of Geophysical Research, 106 (C9), 19883-19901. (doi:10.1029/2000JC000534).

Record type: Article

Abstract

A three-dimensional, unsteady, nonlinear, high-resolution model is used to investigate the impact of the Calvi Canyon (NW Corsica) steep topography on the shelf-slope exchanges as well as on the circulation in the Calvi Bay in homogeneous winter and early spring conditions. A double ? coordinate system is considered in order to represent adequately the high depth gradients within the canyon. The studied region is under the influence of the West Corsica Current flowing northeastward along the NW Corsican coast (right-bounded flow). Model results show that the circulation in the Calvi Bay is determined by flow modifications in the canyon area. The mean horizontal flow is deviated southwestward upstream of the canyon to form an anticyclonic gyre in the western part of the Calvi Bay. Within the canyon the circulation is cyclonic leading to an offshore flow downstream of the canyon. Around the canyon rim, the cross-shelf currents become important, indicating that this region acts as a transition zone of high exchange between nearshore and offshore areas. Furthermore, the canyon topography generates high downwelling (upwelling) and downsloping (upsloping) velocities responsible for an intense vertical transport of material in the area. Numerical runs are performed for typical prevailing wind conditions. The wind is responsible for a drastic increase of cross-shore transports between the bay and the canyon area (3–4 times larger than in the no-wind case). SW winds induce a further enhancement of cross-shelf exchanges, whereas the effect of N-NE winds is to reduce exchange at the shelf break apart from the canyon head where an intense offshore flow occurs. Within the canyon, high vertical velocities are shown to be associated with high cyclonic vorticity which is enhanced (reduced) by the N-NE (SW) wind event. A comparison between model results and measured distributions of nitrate and chlorophyll a concentrations in the area shows the role played by this specific hydrodynamics as a strong constraint on the coastal pelagic ecosystem.

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Published date: 15 September 2001
Organisations: Physical Oceanography

Identifiers

Local EPrints ID: 365223
URI: http://eprints.soton.ac.uk/id/eprint/365223
ISSN: 0148-0227
PURE UUID: 192d74c1-e9b0-4f02-9b82-894a592c5752
ORCID for N. Skliris: ORCID iD orcid.org/0000-0002-2473-2586

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Date deposited: 28 May 2014 09:45
Last modified: 15 Mar 2024 03:39

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Author: N. Skliris ORCID iD
Author: A. Goffart
Author: J.H. Hecq
Author: S. Djenidi

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