Closure of the sea surface height budget with a Stokes offset

TL;DR

This paper demonstrates that the sea surface height budget can be closed using GPS buoy data by accounting for the Stokes offset caused by non-hydrostatic waves, with implications for satellite altimetry calibration.

Contribution

It shows that interpreting GPS buoy measurements as Lagrangian allows for closure of the sea surface height budget by including the Stokes offset.

Findings

The sea surface height budget closes within uncertainties when using GPS buoy data.

The Stokes offset can reach up to 16 cm in observed conditions.

Accounting for the Stokes offset improves the accuracy of sea surface height measurements.

Abstract

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 non-hydrostatic 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.