Estimates of the Regional Distribution of Sea Level Rise over the 1950 to 2000 Period

Abstract

TOPEX/Poseidon satellite altimeter data are used to estimate global empirical orthogonal functions that are then combined with historical tide gauge data to estimate monthly distributions of large-scale sea level vafiability and change over the period 1950-2000. The reconstruction is an attempt to narrow the current broad range of sea level rise estimates, to identify any pattern of regional sea level rise, and to determine any variation in the rate of sea level rise over the 51-yr period. The computed rate of global-averaged sea level rise from the reconstructed monthly time series is 1.8 ∓ 0.3 mm yr-1. With the decadal variability in the computed global mean sea level, it is not possible to detect a significant increase in the rate of sea level rise over the period 1950-2000. A regional pattern of sea level rise is identified. The maximum sea level rise is in the eastern off-equatorial Pacific and there is a minimum along the equator, in the western Pacific, and in the eastern Indian Ocean. A greater rate of sea level rise on the eastern North American coast compared with the United Kingdom and the Scandinavian peninsula is also found. The major sources of uncertainty are the inadequate historical distribution of tide gauges, particularly in the Southern Hemisphere, inadequate information on tide gauge signals from processes such as postglacial rebound and tectonic activity, and the short satellite altimeter record available to estimate global sea level covariance functions. The results demonstrate that tide gauge records will continue to complement satellite altimeter records for observing and understanding sea level change.