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Steady Coastal Circulation on a Narrow Irregular Shelf

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  • 1 University of New South Wales, University College, Australian Defence Force Academy, Canberra, Australia
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Abstract

An analytical model for the continental shelf water level and current response to external forcing (wind or ocean sea level) is presented. Similar analytical models, called arrested topographical waves, have been developed for many geometries, but usually with constant shelf section along the coastline. The model described here is an extension for shelf plans of varying form, the only restriction being that the cross-sectional profile must scale with the shelf width. Cross-sectional profiles of linear, parabolic, and exponential shape and alongshore forcing profiles of harmonic and constant form are included. The shelf response behavior is similar to that demonstrated by the models with constant section except for across-shelf penetration of the forcing condition, which is markedly affected by local shelf width. In particular, large variations in alongshore currents can occur with modest variations in shelf width.

Application of the irregular planform model to the New South Wales (Australia) shelf demonstrates that some of the observed long-term features can be accounted for by forcing at the shelf edge associated with gradients in the East Australian Current. Shelf-edge profiles can he found that provide a match of coastal gradients, measured nearshore currents, and reported shelf-edge currents.

Abstract

An analytical model for the continental shelf water level and current response to external forcing (wind or ocean sea level) is presented. Similar analytical models, called arrested topographical waves, have been developed for many geometries, but usually with constant shelf section along the coastline. The model described here is an extension for shelf plans of varying form, the only restriction being that the cross-sectional profile must scale with the shelf width. Cross-sectional profiles of linear, parabolic, and exponential shape and alongshore forcing profiles of harmonic and constant form are included. The shelf response behavior is similar to that demonstrated by the models with constant section except for across-shelf penetration of the forcing condition, which is markedly affected by local shelf width. In particular, large variations in alongshore currents can occur with modest variations in shelf width.

Application of the irregular planform model to the New South Wales (Australia) shelf demonstrates that some of the observed long-term features can be accounted for by forcing at the shelf edge associated with gradients in the East Australian Current. Shelf-edge profiles can he found that provide a match of coastal gradients, measured nearshore currents, and reported shelf-edge currents.

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