Effects of longshore shelf variations on barotropic continental shelf waves,slope currents and ocean modes |
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| Institution: | 1. Institut de Ciències del Mar (ICM-CSIC), Barcelona, Spain;2. TRAGSATEC-Secretaria General de Pesca, Madrid, Spain;3. Marine Geoscience National Oceanography Centre (NOC), Southampton, United Kingdom;4. Universitat Autònoma de Barcelona (UAB), Bellaterra, Spain;5. Oceans Institute and School of Physics, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;6. School of Natural Sciences and Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, WA, Australia;7. Instituto Español de Oceanografía (IEO), Madrid, Spain;1. Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA;2. U.S. Geological Survey, New Jersey Water Science Center, Lawrenceville, NJ 08648, USA;3. Department of Ecology, Evolution, & Natural Resources, Rutgers University, New Brunswick, NJ 08901, USA;4. Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14850, USA;5. Department of Statistics, Columbia University, New York, NY 10027, USA;6. Department of Statistics, University of Chicago, Chicago, IL 60637, USA |
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| Abstract: | Effects of continental shelf bends, converging depth contours and changing depth profiles are discussed. Some analysis is carried out for previously unstudied cases. Separate oceanic interior and shelf flow problems are formulated for a sufficiently narrow shelf. The ocean interior ‘sees’ only an integrated shelf effect, typically increasing shelf-edge amplitudes, retarding longshore Kelvin-wave propagation and increasing natural mode periods by 0 (10%). On the local shelf, the flow matches to the ocean interior and is nondivergent. Effects on shelf waves and slope currents depend subtly on the nature of the longshore variations. Curvature and contour convergence do not per se imply scaterring or generation of shelf waves. Indeed, any depth h(ξ) where ▽2 ξ(x,y) = 0 (a condition approximating longshelf uniformity in the topography's convexity) supports essentially the same shelf waves as do straight depth contours (DAVIS, 1983), and slope currents follow depth contours. Scattering results rather from breaks in analyticity of the depth profile. Hence calculations for small isolated features (necessarily highly convex or concave) may overestimate scattering, and superposition for realistic topography may lead to much self-cancellation among scattered waves. Otherwise, examples show a strong preference for scattering into adjacent mode numbers and into any shelf wave mode near to its maximum frequency. A shelf sector, where the maximum shelf wave frequency maxω is less than the frequency ω of an incident shelf wave, causes substantial scattering unless maxω and ω are very close. Adjustment of slope currents to changed conditions takes place through (and over the decay distance of) scattered shelf waves. |
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