General circulation models offer a way to estimate the impact of mass redistributions on the Earth's time-varying gravity field. In this way, the prospects for detecting climate signals in the gravity field by dedicated satellite gravity missions, such as Gravity Recovery and Climate Experiment (GRACE), can be assessed. Using monthly averaged fluid mass diagnostics from a coupled atmosphere-ocean model developed at the Goddard Institute for Space Studies (GISS), we have estimated geoid variations from the fundamental model mass components. From these estimates the seasonal geoid signals from sea level, snow, soil moisture, water vapor, and atmospheric mass can be compared to the estimated errors for GRACE. All of these seasonal mass flows from the GISS model are well above the preliminary GRACE measurement errors. In addition, mass flows with significant secular trends attributable to the model's simulated increase of greenhouse gases would, in principle, be detectable by GRACE. However, the interannual variability of mass flows may require longer time series of gravity data, pattern analysis, or modeling improvements in order to detect trends.