HR: 1400h
AN: OS33A-03    [Abstracts]
TI: Reconstruction of past decades sea level using thermal expansion, tide gauge and satellite altimetry data
AU: * CAZENAVE, A
EM: anny.cazenave@cnes.fr
AF: LEGOS-CNES, OMP, 18 Avenue E. Belin , Toulouse, 31400, France
AU: Berge-Nguyen, M
EM: muriel.berge@cnes.fr
AF: LEGOS-CNES, OMP, 18 Avenue E. Belin , Toulouse, 31400, France
AU: Lombard, A
EM: lombard@legos.obs-mip.fr
AF: LEGOS-CNES, OMP, 18 Avenue E. Belin , Toulouse, 31400, France
AU: Cretaux, J
EM: jean-francois.cretaux@cnes.fr
AF: LEGOS-CNES, OMP, 18 Avenue E. Belin , Toulouse, 31400, France
AB: Several studies have developed methods for reconstructing past 2-D time series of oceanographic fields (e.g., sea surface temperature, sea surface height, surface pressure) by combining 2-D data of limited temporal coverage (in general available from satellite observations over the last 2 decades or less) with historical (several decades-long), sparse 1-D records. EOF spatial modes of the gridded data are fitted to the 1-D records to provide reconstructed long-term 2-D fields. An implicit assumption of the method is that spatial patterns of the EOF leading modes computed from the short-term 2-D fields are stationary. The objective of the present study is to test the influence of the temporal coverage of the 2-D fields on the reconstructed signal. For that purpose we use global grids of steric sea level data, available over the last 53 years. Global sea level trends computed over that period are used as reference. The 50-year long reconstructed steric sea level signal is computed using different time spans (in the range 10-50 years) for the EOF decomposition. Different geographical distributions for the 1-D steric 53-year long steric sea level time series (interpolated at specific locations from the 2-D grids) are also considered. Then we determine thresholds (in terms of 2-D fields temporal coverage and 1-D records spatial distribution) for which the reconstructed 2-D fields are correctly recovered. In a second step, we apply the method for reconstructing 2-D sea level data over the past 53 years, combining sparse tide gauge records with 2-D steric sea level EOFs computed over the last 53 years. In effect, several recent studies have shown that the spatial patterns of sea level trends recovered by satellite altimetry are very similar as those of the steric sea level. We also reconstruct past sea level over 1950-2003 using 2-D grids of satellite altimetry sea level over 1993-2003. We focus on spatial patterns of reconstructed sea level trends as well as on the global mean sea level. Comparison of reconstructed sea level with tide gauge records is also performed. The two methods of past sea level reconstruction(ie, spatial covariances based on thermal expansion grids and satellite altimetry)are compared and discussed.
DE: 1222 Ocean monitoring with geodetic techniques (1225, 1641, 3010, 4532, 4556, 4560, 6959)
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1641 Sea level change (1222, 1225, 4556)
DE: 4500 OCEANOGRAPHY: PHYSICAL
DE: 4556 Sea level: variations and mean (1222, 1225, 1641)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly