Continental-shelf-scale model of the Leeuwin Current
Abstract:A simple model is presented for the poleward eastern boundary current (the Leeuwin Current) off Western Australia. For continental-shelf length-scales and seasonal time-scales, the advective and time-derivative terms are small, and water flows onto the shelf until a sufficient cross-shelf pressure gradient is set up to push the same flux back. In a rotating system, the return flux takes place in a frictional (Ekman) layer at the bottom, and is synonymous with a near-bottom longshore current B, from
−CD|B|B = ∫O−H 1/ ∂p/∂y dz + u2∗,
which is equatorward close to shore, but poleward past the 40 m isobath. If the mixed layer is deep enough, there is no upwelling, despite the upwelling-favorable winds. The light surface water is pushed down, causing a baroclinic shear enhancing the poleward current. Advection causes an intense sloping density, salinity, and tracers front. Observed u2∗ and Py from Western Australia predict B to be poleward in early winter at about 0.2 m s−l, and near zero in summer. The sea-level-slope gy correlates highly (r = 0.9) with the wind-stress u2∗ with a regression of (100 m)−1, both along Western Australia and western North America.
Document Type: Research Article
Publication date: 1987-11-01
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