Lookup NU author(s): Emeritus Professor Robin Johnson
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© 2018 Elsevier Ltd The ideas and methods typically associated with classical fluid mechanics are briefly introduced and then applied to some problems in physical oceanography. The main thrust is to show that this approach is surprisingly successful, avoiding the need to invoke any modelling (based, for example, on physical principles without an accompanying derivation) or to implement numerical methods. The governing equations in a spherical, rotating coordinate system are presented, together with a suitable non-dimensionalisation, leading to a discussion of the available asymptotic approximations. The tangent plane, and f- and β-plane approximations, are also mentioned. A number of examples (inviscid), taken from the recent literature, are described, with the emphasis on the formulation and methods employed. The first, used as an introduction to the ideas, is based on the β-plane approximation and describes the slow evolution of the flow along the Pacific Equator (the EUC); a fully three-dimensional, nonlinear flow structure is constructed. The next pair of examples (which are quite closely related) are exact solutions of the full set of governing equations; one relates to the velocity profile typical of the EUC, and the other to the jet-like flow structures that contribute to the Antarctic Circumpolar Current. The final example shows how a theory for (nonlinear) large gyres, rotating in the thin ocean layer on the surface of a sphere, can be constructed. A few general comments and observations are made in conclusion.
Author(s): Johnson RS
Publication type: Article
Publication status: Published
Journal: Deep-Sea Research Part II: Topical Studies in Oceanography
Issue: ePub ahead of Print
Online publication date: 03/09/2018
Acceptance date: 02/04/2018
ISSN (print): 0967-0645
ISSN (electronic): 1879-0100
Publisher: Elsevier Ltd
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