A source-Sink laboratory model of the ocean circulation

Abstract

Abstract A two gyre circulation and inertial western boundary currents have been observed in a sloping bottom laboratory model of a barotropic ocean circulation. Water of viscosity v is contained in a rotating (angular velocity ω), square basin of side L (30 cm) with a flat top and a bottom slope (tan θ) such that the depth (H) varies from 12 to 15 cm. The flow is driven by a distributed source and sink at the upper surface, a plate drilled with 342 holes. The hole distribution and size is arranged so that the average imposed vertical velocity, w = w 0 sin (2πy′/30), models the Ekman divergence from a two gyre zonal wind stress. Fluid flow is observed with the thymol blue technique over the ranges of Rossby numbers (w 0/2ωL tan θ) from 1.44 × 10−3 to 1.41 × 10−2 and Ekman numbers (v/2ωH 2) from 2.13 × 10−5 to 2.10 × 10−3. At the largest Rossby numbers the flow pattern changes markedly, but the non-uniformity of the imposed vertical velocity also penetrates deep into the fluid in this regime.