HR: 14:20h
AN: OS12B-03    [PDF]
TI: Contribution of Thermal Expansion to Observed Sea Level Rise During the Past Decade
AU: * Lombard, A
EM: lombard@notos.cst.cnes.fr
AF: LEGOS / GRGS, 18 Av. E. Belin, TOULOUSE, 31400 France
AU: Cazenave, A
EM: cazenave@cnes.fr
AF: LEGOS / GRGS, 18 Av. E. Belin, TOULOUSE, 31400 France
AU: Letraon, P
EM: Pierre-Yves.Letraon@cls.fr
AF: CLS, 8-10 rue Hermes Parc Technologique du Canal, Ramonville Saint-Agn, 31526 France
AB: Recent studies by Cabanes et al. (2001) and Cabanes (2003) have suggested that thermal expansion of the oceans is likely to be the main cause of observed sea level rise during the recent years. These results were based on a single ocean temperature data set (Levitus et al., 2000) and the comparison with the Topex/Poseidon global mean sea level rise was limited to a 6-year period (1993-1998). In this study, we have compared 3 different ocean temperature data sets to investigate more precisely the steric contribution to sea level rise : the Levitus et al.'s (2000) and Ishii et al.'s (2003) data, which both provide $1\deg\times1\deg$ gridded temperature fields for the upper 500m over 1950-1998, and in situ hydrographic data (temperature and salinity from various sources) collected during the WOCE experiment over 1993-2001. We analysed these data in terms of both temporal global mean steric sea level variations and spatial steric sea level trends. Over 1993-1998 (the period of overlap with Topex/Poseidon observations), computed steric sea level trends based on Ishii et al. and Levitus et al. data show similar spatial patterns. However the Ishii et al.'s map appears smoother, showing less high-frequency signal than Levitus et al.'s trend map. In addition, significant difference between temporal global mean sea level curves is observed, reflecting possible differences in both analysis schemes. When such a comparison is extended over the 1950-1998 time span, less difference is noticed between the two data sets prior to 1990. Inclusion of numerous in situ data over the central Pacific during the 1990s in the Ishii et al.' objective analysis may be the cause of the discrepancy observed with Levitus et al's data set. In another analysis, we compared both data sets with in situ hydrographic data from WOCE, by interpolating the Ishii and Levitus grids at the locations of the in situ temperature measurements on their overlapping period 1993 -1998. A very good agreement was found between steric sea level curves based on WOCE data and Levitus data. Finally we computed the steric contribution over 1993-2001 using the WOCE data and compared with the Topex/Poseidon sea level observations. This comparison confirmed earlier results from Cabanes (2003), i.e., during the past decade, thermal expansion appears to be the dominant contribution to the observed sea level rise.
DE: 1635 Oceans (4203)
DE: 4215 Climate and interannual variability (3309)
DE: 4556 Sea level variations
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting