A 20th century acceleration in sea level rise and decadal impact on GMSL of volcanic eruptions
John Church(1) and Neil White(1)
CSIRO Marine and Atmospheric Research,
GPO Box 1538,
Multi-century sea-level records and climate models indicate an acceleration of sea-level rise, but no 20th century acceleration has been detected. A reconstruction of global sea level using tide-gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea-level rise but no significant acceleration over this period. We extend the reconstruction of global mean sea level back to 1870 and find a sea-level rise over the period January 1870 to December 2004 of 195 mm, a 20th century rate of sea-level rise of 1.7 +/- 0.3 mm yr^-1 and a significant acceleration of sea-level rise of 0.013 +/- 0.006 mm yr^-2. This acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed. If this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm, consistent with projections in the IPCC TAR.
From 1960 to 2000, volcanic eruptions contribute to the interannual variations in the rate of sea-level rise. Ocean observations and a set of climate simulations show that large volcanic eruptions result in rapid decreases in ocean heat content and global mean sea level (about 3 x 10^22 J and 5 mm for the Mt Pinatubo eruption). The recovery of sea level following the Mt Pinatubo (1991) eruption contributes significantly to the difference between the 1950 to 2000 rate of sea-level rise (1.8 mm yr^-1) and the higher rate estimated for the modern satellite altimeter era (3.2 mm yr^-1 for 1993-2000).