The mean seasonal cycle in relative sea level from satellite altimetry

Satellite altimetry is used to determine themean seasonal cycle in relative2 sea level, a quantity relevant to coastal flooding and related applications. The main3 harmonics (annual, semiannual, terannual) are estimated from 25 years of gridded4 altimetry, while several conventional altimeter ‘corrections’ (gravitational tide, pole5 tide, and inverted barometer) are restored. To transform from absolute to relative6 sea levels, a model of vertical land motion is developed from a high-resolution7 seasonal mass inversion estimated from satellite gravimetry. An adjustment for8 annual geocenter motion accounts for use of a center-of-mass reference frame9 in satellite orbit determination. A set of test tide gauges, from which seasonal harmonics have been estimated from hourly measurements, is used to assess how11 accurately each adjustment to the altimeter data helps converge the results to true12 relative sea levels.