[G04-3] Earth rotation and geodynamics III

[G04-3-04] Constraining vertical land motion of tide gauges (IAG JWG 3.2): combination of velocity fields

^○Alvaro Santamaria-Gomez¹, Matt King², Tilo Schone³, Tonie van Dam⁴, Guy Woppelmann⁵ (1.Universite de Toulouse, GET, OMP, Toulouse, France, 2.University of Tasmania, School of Land and Food, Hobart, Australia, 3.Helmholtz Centre Potsdam GFZ, Potsdam, Germany, 4.University of Luxembourg, Faculte des Sciences, de la Technologie et de la Communication, Luxembourg, 5.LIENSs, Universite de La Rochelle/CNRS, La Rochelle, France)

The Joint Working Group 3.2 of the International Association of Geodesy aims at providing contrasted vertical land motion estimates at tide gauges commonly used for long-term sea-level change and for calibration/validation of satellite altimeters.

We present the combination and comparison of available global vertical velocity solutions from GPS and DORIS techniques. Up to 20 individual and 4 combined solutions have been compiled; they include solutions using different GPS processing approaches (differenced and undifferenced), different time series lengths and different approaches to assess velocity uncertainty. The combined vertical velocity solution contains 1132 stations for which at least 3 different estimates were available. After aligning and weighting the solutions, the repeatability of the vertical velocity estimates varies among the stations between 0.1 mm/yr and more than 1 mm/yr, with a median station repeatability of 0.3 mm/yr. These velocity repeatability estimates represent an empirical approach to assess velocity uncertainty and their median value is in agreement with uncertainty assessments accounting for the auto-correlation of the time series.