Impacts of the ocean lateral diffusion on the El Niño/Southern Oscillation-like variability of a global coupled General Circulation Model

A global coupled General Circulation Model is used to investigate effects of the lateral ocean mixing on the amplitude and spectral characteristics of the ENSO-like variability. Three 40-year coupled simulations are analysed. They only differ by the lateral ocean physics parametrized: a horizontal diffusion scheme; an isopycnal scheme ; isopycnal scheme with an Eddy Induced Velocity (EIV) term. The Multichannel Singular Spectrum Analysis is used to extract linear modes of variability from each simulation and from observations. The strength of the variability, close to that observed in the horizontal and only-isopycnal simulations, is stronger in the two isopycnal configurations, and more especially when the EIV is added. The dominant periods of the variability, also close to those observed, are also affected by the lateral diffusion: the time scale becomes slightly longer as the complexity of the lateral physics increases.