HR: 1340h
AN: G53A-0105    [Abstracts]
TI: Absolute local sea surface in the Vanuatu Archipelago from GPS, satellite altimetry and pressure gauge data
AU: * Cheng, K K
EM: cheng.168@osu.edu
AF: Departement of Civil and Environmental Engineering and Geodetic Science, the Ohio State University, 2070 Neil Ave, Columbus, OH 43210 United States
AU: Ballu, V
EM: ballu@ipgp.jussieu.fr
AF: D‚partement de G‚ophysique Spatiale et Plan‚taire, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75252 France
AU: Bouin, M
EM: bouin@ensg.ign.fr
AF: LAREG/ENSG, Cite Descartes 6-8 av Blaise Pascal, Marne la Vallee, 77455 France
AU: Calmant, S
EM: stephane.calmant@cnes.fr
AF: Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales, CNES-CNRS-IRD-UPS, Observatoire de Midi-Pyrenees, 18, Avenue Edouard Belin, Toulouse, 31401 France
AU: Shum, C
EM: ckshum@osu.edu
AF: Departement of Civil and Environmental Engineering and Geodetic Science, the Ohio State University, 2070 Neil Ave, Columbus, OH 43210 United States
AB: Water height measurements provided by seafloor tide gauges are a combination of sea level variation and local ground motion. Both signals are of scientific interest, but they must be separated in order to be useful. A reliable estimation of the vertical ground motion is important in very seismically areas such as the Pacific Ocean rim. One promising method to separate the two contributions is to use satellite altimetry which gives absolute water height that is independent of the local ground motion. However, the altimeter data must be calibrated using ground truth measurements. Once different components of the signal are separated, bottom pressure gauges can be used to detect vertical movements of the seafloor. The Vanuatu Archipelago is part of the Pacific "ring of fire", where plates are quickly converging. In this area, movements are very rapid and the seismic activity is intense, which gives a good opportunity to study deformation and seismic cycle. To get an integrate picture of vertical deformation over one plate and between the two plates, one needs to be able to monitor vertical movements on both underwater and emerged areas. We conducted an experiment in this area to compare measurements from bottom pressure gauges located beneath altimetry satellite tracks with sea surface altitude measurements from GPS. Two bottom pressure gauge are immerged since Nov. 1999 in this region. In order to perform absolute calibration for multiple satellite altimeters that overfly the region, we conducted 2 campaigns of GPS measurements of instantaneous sea surface height onboard the R/V Alis and using a GPS buoy. We present results of GPS computations for the March 2003 and March 2004 campaigns. These sea level GPS measurements are compared with multiple altimeter-measured sea surface heights, and sampling differences and high frequency variations were removed using continuous pressure gauge data. The observed discrepancies are likely to be explained by local geoid variations or dynamic topography and we conducted GPS surveys to map these differences.
DE: 4294 Instruments and techniques
DE: 4556 Sea level variations
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting