Sea level changes from Topex-Poseidon altimetry and tide gauges, and vertical crustal motions from DORIS

Sea level difference (Topex-Poseidon minus tide gauge) time series have been computed over 1993-1997 at 53 selected gauges sites. Comparison of these sea level differences with vertical crustal motions derived from the DORIS space geodesy system at 6 colocated sites shows good consistency. At one site (the Socorro volcanic island), a striking correlation is reported between sea level differences and DORIS height time series. The observed trend likely reflects a post eruptive deformation associated with a volcanic eruption that occurred in early 1993. At several other gauge sites, the sea level differences present large linear trends possibly bearing evidence of land motion. This may be the case at Rabaul (Papua New Guinea) where a volcanic eruption took place in autumn of 1994. The sea level differences at Rabaul show a negative trend from this date, likely related to the volcanic event.