Advanced Ocean Modelling: Using Open-Source Software

122 4 2.5D Vertical Slice Modellingwind-stress forcing imposed creates low-amplitude internal waves at the pycnocline.Baroclinic compensation is evident from the weakening of geostrophic flows belowthe pycnocline.In the real situation and away from the western boundaries of ocean basins, thedivergence of transports in the surface Ekman layer is compensated by a convergenceof geostrophic flow owing to meridional variation of the Coriolis parameter;that is, the so-called β effect. The configuration of this exercise does not reproducethis balance, known as the Sverdrup balance. Nevertheless, the principal mechanisminherent with the baroclinic compensation process is the same.4.6.5 Results: Scenario 2The wind-stress forcing displayed in Fig. 4.17b creates a convergence of surfaceEkman-layer transports such that the sea level rises in the middle of the modeldomain (Fig. 4.21). In equilibrium, this surface convergence is compensated by adivergence of lateral flow in the bottom Ekman layer, inducing a downward displacementof the pycnocline. As in Scenario 1, modulation of the internal densityfield leads to a weakening of the geostrophic flow below the pycnocline.Again, the geostrophic surface flow runs largely into the same direction as thewind (Fig. 4.22). The following exercise will demonstrate that this is not a generalrule.Fig. 4.21 Exercise 19. Same as Fig. 4.19, but for Scenario 2