Abstract
We studied shocks in a coastal boundary current with zero potential vorticity. By coastal boundary current, we mean a semigeostrophic light fluid flow over an infinitely deep dense fluid and along a coast on its right hand side, with its lower interface exposed to the ocean surface at some finite distance from the coast. The shocks are assumed to conserve mass and momentum. It is found that the shocks can be classified into two categories, “coastal shocks” and “frontal shocks”, by the signs of the upper layer flux relative to the shocks. Coastal shocks, for which the relative upper layer flux is negative, always propagate downstream. The upper layer at the coast is thicker on the upstream sides of coastal shocks than on the downstream sides. Frontal shocks, for which the relative upper layer flux is positive, propagate upstream as well as downstream. In most cases, the current is wider on the downstream sides of frontal shocks than on the upstream sides. However, under the circumstances that the current is nearly separated from the coast, the current is wider on the upstream sides of frontal shocks. Coastal and frontal shocks both dissipate energy of the current. We also demonstrate that special shocks with no light fluid on the downstream sides cannot exist irrespective of the potential vorticity distribution.
Similar content being viewed by others
References
Benjamin, T. B. (1968): Gravity currents and related phenomena.J. Fluid Mech.,31, 209–248.
Griffiths, R. W. and E. J. Hopfinger (1983): Gravity currents moving along a lateral boundary in a rotating fluid.J. Fluid Mech.,134, 357–399.
Kubokawa, A. and K. Hanawa (1984a): A theory of semigeostrophic gravity waves and its application to the intrusion of a density current along a coast. Part 1. Semigeostrophic gravity waves.J. Oceanogr. Soc. Japan,40, 247–259.
Kubokawa, A. and K. Hanawa (1984b): A theory of semigeostrophic gravity waves and its application to the intrusion of a density current along a coast. Part 2. Intrusion of a density current along a coast in a rotating fluid.J. Oceanogr. Soc. Japan,40, 260–270.
Landau, L. D. and E. M. Lifshitz (1987):Fluid Mechanics. Pergamon, 532 pp.
Long, R. R. (1954): Some aspects of the flow of stratified fluids. II. Experiments with a two-fluid system.Tellus,6, 97–115.
Nof, D. (1984): Shock waves in currents and outflows.J. Phys. Oceanogr.,14, 1683–1702.
Nof, D. (1987): Penetrating outflows and the dam-breaking problem.J. Mar. Res.,45, 557–577
Pratt, L. J. (1983): On inertial flow over topography. Part 1. Semigeostrophic adjustment to an obstacle.J. Fluid Mech.,131, 195–218.
Pratt, L. J. (1987): Rotating shocks in a separated laboratory channel flow.J. Phys. Oceanogr.,17, 483–491.
Røed, L. P. (1980): Curvature effects on hydraulically driven inertial boundary currents.J. Fluid Mechn.,96, 395–412.
Stern, M. E. (1980): Geostrophic fronts, bores, breaking and blocking waves.J. Fluid Mech.,99, 687–703.
Stern, M. E., J. A. Whitehead and B. L. Hua (1982) The intrusion of a density current along the coast of a rotating fluid.J. Fluid Mech.,123, 237–265.
Whitham, G. B. (1974):Linear and Nonlinear Waves. Wiley & Sons, 636 pp.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Maruyama, K. Shocks in a coastal boundary current. J Oceanogr 52, 139–169 (1996). https://doi.org/10.1007/BF02235667
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02235667