Long term changes of altimeter range and geophysical corrections at altimetry calibration sites

Long term changes in the routinely applied TOPEX/Jason corrections as well as their changes in coastal regions are investigated at four altimetry calibration sites: Bass Strait, Corsica, Gavdos and platform Harvest. Furthermore, alternative corrections are tested to investigate if the use of a different set of corrections will lead to different local and regional sea level changes at those sites. The results show that no significant linear trends in the sum of range corrections are found for the calibrations sites both for local scales (within 50 km around the selected site) and for regional scales (within 300 km). However, the geophysical corrections accounting for atmospheric pressure loading and high frequency sea level variations (dynamic atmosphere correction) that is frequently applied to in situ gauge and the altimeter observations should be considered with care for calibration with in situ observations. Over the 18 years (1993-2010), the dynamic atmosphere correction shows a regional trend close to 1 mm/year at both Mediterranean sites (Corsica and Gavdos).