What is Required to Model the Global Ocean Circulation?

Simulating and forecasting the circulation of the global ocean is a difficult task. The present generation of high-resolution ocean circulation models, with horizontal resolution of 110, appears to be deficient in kinetic energy when compared with long-term observations. A series of near-twin experiments, using the global HYbrid Coordinate Ocean Model HYCOM with identical atmospheric forcing, but varying in horizontal resolution and assimilation of altimetric steric height anomalies, show significant improvement with a better representation of mesoscale eddies when compared to observations. For a 112.5 9 km global model, the eddy kinetic energy EKE at the surface and abyss is low by 21 and 24, respectively, compared to surface drifting buoys and deep current meters. Increasing the model resolution to 125 4.4 km or injecting mesoscale eddies through the assimilation of surface observations in a 112.5 model increases the surface and abyssal EKE to levels consistent with observations.