Equilibrium states of rotating turbulence in a closed basin with topography

A combined experimental and numerical investigation of equilibrium states arising from quasi-two-dimensional turbulent flows in a rotating quadrangular basin with a central flat region and steep slopes adjacent to the sidewalls is presented. The study examines freely decaying and continuously forced regimes. Laboratory experiments show that decaying turbulence consistently evolves into a robust equilibrium state characterised by: (i) a boundary current around the basin along the topographic contours, and (ii) a central anticyclone – features accurately reproduced by shallow-water numerical simulations at laboratory scale. Additional simulations using a mesoscale basin suggest the relevance of these findings to oceanic regimes for different initial conditions and topographic parameters. In the case of continuously forced flows, time-averaged fields reveal qualitatively similar structures, despite the randomness of the applied forcing and the consequent absence of a strict equilibrium. These results demonstrate the emergence of robust flow patterns with implications for the modelling and understanding of semi-permanent flows that are often found in statistical theories of geophysical turbulence.