ALTIGAPS: a Global Synthesis of Multisatellite Altimetry, Tide Gauge and GPS

Abstract:

We present the global database ALTIGAPS. Multisatellite altimetry is combined with tide gauges and Global Positioning System (GPS) measurements to close the sea level budget at coasts. The technical characteristics of ALTIGAPS are given: vertical land motions and sea level variations are estimated simultaneously for a network of 886 ground stations, with accuracies better than 1.7 mm/yr. Examples of the applications empowered by ALTIGAPS are discussed. In particular, the role of vertical land motions in relative sea level variations is explored to better understand the natural hazards associated with sea level rise in coastal areas. Global evidence for the local variability in vertical land motions is provided, which may either amplify or attenuate the apparent rise of the sea at the coast. A set of 182 potential vulnerable localities are identified by large coastal subsidence which increases by several times the effects of climate-induced sea level rise. Finally the benefit and limitations of ALTIGAPS are reviewed, and guidance for future improvement is given.