[1] The sub-monthly portion of a recent daily-resolution GRACE data set (ITG-Grace2010) is evaluated over the ocean by comparing with the high-frequency component of sea level variability measured by satellite altimetry. The current Atmosphere and Ocean De-aliasing (AOD) model used to remove the high-frequency non-tidal ocean mass variations in GRACE data processing is also assessed. We demonstrate that the OMCT-based AOD model does not adequately represent the true sub-monthly variability in non-tidal ocean mass variability, but that ITG-Grace2010 does. The differences are not small, and indicate that a new model, or a data set derived from sub-monthly GRACE information, should be considered for de-aliasing in future GRACE processing.