The twin assimilation experiments indicate that the effectiveness of a data assimilation method depends on initial perturbation.

For the imperfect initial condition case in which the T/S fields are perturbed, the EnKF works efficiently in restoring the true ocean state (RMS errors reduce by 75% over a time scale of ~10 days).

For imperfect model configuration case in which the wind and heat flux fields are perturbed, the EnKF is constrained more by wind field than heat flux. In winter, the wind dominates the effectiveness,while in summer, both wind and heat flux seem equally important.

Since the data assimilation works only under small e values,  it is more important to improve the accuracy of the forcing driving the model before the data assimilation is used.
Major results of OSSEs