Since the Earth's gravitational field is relatively stable on decadal to centennial timescales, ocean circulation plays a more significant role in the observed variation of SSH. Across the seasonal cycle changes in patterns of warming, cooling and surface wind forcing affect circulation and influence SSH. Variations in SSH can be measured by satellitealtimetry (e.g. TOPEX/Poseidon) and used to calculate determine sea level rise and properties such as ocean heat storage.