The effect of numerical parameters on eddies in oceanic overflows: a laboratory and numerical study

Overflows in the ocean occur when dense water flows down a continental slope into less dense ambient water. It is important to study idealized and small-scale models, which allow for confidence and control of parameters. The work presented here is a direct qualitative and quantitative comparison between physical laboratory experiments and lab-scale numerical simulations. Physical parameters are varied, including the Coriolis parameter, the inflow density, and the inflow volumetric flow rate. Laboratory experiments are conducted using a rotating square tank and high-resolution camera mounted on the table in the rotating reference frame. Video results are digitized in order to compare directly to numerical simulations. The MIT General Circulation Model (MITgcm), a three-dimensional ocean model, is used for the direct numerical simulations corresponding to the specific laboratory experiments. It was found that the MITgcm was not a good match to laboratory experiments when physical parameters fell within the high eddy activity regime. However, a more extensive resolution study is needed to understand this fully. The MITgcm simulations did provide a good qualitative and quantitative match to laboratory experiments run in a low eddy activity regime. In all cases, the MITgcm simulations had more eddy activity than the laboratory experiments.