We investigate a wind-driven subtropical gyre in a two-layer quasigeostrophic model with weak interfacial and bottom friction. Asymptotic analysis shows that the steady lower-layer flow in the pool of closed geostrophic contours is of higher order with respect to eddy momentum transfer than the barotropic flow, so that the pool circulation including a narrow northward current is determined by a local forcing-dissipation balance with flow paths being prescribed. Since the geostrophic contours are blocked west of the pool, the inner western boundary layer is an analogue of Welander's layer which can be matched with the interior and hence cannot be active. It is also shown that there exist steady states in which the lower-layer potential vorticity in the pool becomes substantially uniform. The homogenization process is dominated by advection and thus completed within a single passage through the gyre. This is because an O(1) anomaly of potential vorticity that is comparable to the value at the pool boundary can be produced in the boundary layer by westward intensification of gyre-scale vorticity inputs via friction, however weak it may be, and is then transported to the interior by the characteristic flow to fill the pool. This style of homogenization occurs if the ratio of the friction coefficients, which determines the strength of the initial anomaly and deviations from downgradient diffusion, falls into specific ranges.
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