Atmospherically forced, high-frequency oceanic variability is investigated using different configurations of an ocean general circulation model. At periods less than 20 days, the dynamic response of the sea surface to pressure loading exceeds that due to wind stress, and is mostly barotropic. Energy at these periods aliases into satellite altimeter measurements of sea surface height (SSHT). The global variance of collinear (≈10 day) differences of this modelled aliased SSHT is between (2 cm)2 and (3.5 cm)2, depending on the model configuration used. The local variance can reach (14 cm)2 at some high latitude locations. We use the ocean model predictions to remove the high-frequency signals from TOPEX/Poseidon (T/P) observations. We obtain a global variance reduction in collinear differences of up to (2 cm)2, about 7% of the T/P signal. Our model has difficulty in predicting the variability at periods less than 5 days. ¿ 2000 American Geophysical Union