Closure of the Sea Surface Height Budget with a Stokes Offset

The sea surface height budget, obtained by integrating hydrostatic balance over the water column, relates sea surface height variations to variations of the seafloor pressure, density in the water column, and atmospheric surface pressure. This budget is crucial for calibrating and interpreting satellite altimetry measurements. It only holds once nonhydrostatic surface gravity waves are averaged out, however, which complicates an observational closure of the budget. Using data from the California Current System, this study demonstrates that the budget closes to within understood uncertainties if GPS buoy measurements of surface height are interpreted as Lagrangian measurements. The buoy largely follows wave motion and spends slightly more time near wave crests than troughs. The associated Stokes offset, which reaches a maximum of 16 cm in these observations, must be accounted for in the Eulerian sea surface height budget.