Although sea level has varied very little over the last millennia (geological observations indicate that the sea level rise did not exceed about 0.1 mm/yr in the last 3000 years), tide gauge records report a rate of sea level rise of 1.5 - 2mm/yr since the beginning of the 20th century.
Recent re estimates of the rise in sea level for the period 1950-2000, using records from high-quality, historical tide gauges provide a rate of ~1.8 mm/year. Most recent results, based on satellite altimetry, indicate a rate of sea level rise of 3.3 mm/yr for 1993-2005. The GOHS team is involved in measuring sea level from altimetry observations from the Topex/Poseidon and Jason-1 missions.
Figure 1 shows the global mean sea level curve based on Topex/Poseidon data since 1993 and Jason-1 data since 2001. The mean rise observed between January 2003 and mid-2005 is 3.0±0.4 mm/yr. After correction of the post-glacial rebound effect (due to crust and mantle readjustment since last deglaciation) gives a rate of a sea level rise of ~3.3 mm/yr for the last 13 years (Cazenave and Nerem, 2004).
Figure 1 :Mean sea level curve from satellite altimetry (1993-2006)
(Topex/Poseidon et Jason-1)
Regional sea level trend distribution mapping is available thanks to the global coverage of altimetry data (Figure 2). In some regions (Western Pacific and Eastern Indian Ocean), sea level has been rising up to 5-10 times faster than average over the 1993-2006 period. In other regions (Eastern Pacific and Western Indian Ocean), the sea level has dropped over this period. The geographical distribution of sea level trends appears quite stable over the 14-year analysis period.
Figure 2 : Geographical distribution of sea level trends (1993-2006)
d'après Topex/Poseidon et Jason-1
Figure 3 : Carte de la distribution géographique des vitesses de variation du niveau de la mer (1993-2006)
based on Topex/Poseidon data and Jason-1