Vertical deformation and sea level changes in the coast of Chile by satellite altimetry and tide gauges

Abstract

Located at the intersection of the triple junction between the Nazca, South American, and Antarctic plates, the Chilean territory is subject to active lithospheric deformations and seismicity. Taking the difference between the satellite altimetry (ALT) data that give the absolute sea level variation and the tide gauge (TG) observations that record the relative sea level variation, we computed the absolute vertical crustal motion of the TG sites. We used 11 TG stations along the Chilean coast and altimeter measurements from multi-satellite missions (Topex, Jason-1 (A), and Jason-2) in nearby waters. The ALT-TG vertical deformations were compared with trends obtained from GPS measurements, which showed good consistency in terms of a correlation coefficient of about 0.9 (in 8 of 11 stations). Our results reveal that the behaviour of the long-term vertical deformations along the Chilean coast presented an important spatial variability. We also estimated the sea level change (SLC) through a multivariate model involving linear trend and decadal and inter-decadal climatic influence; in addition, the glacial isostatic adjustment effect was also removed. Our estimation of the SLC in the Chilean coast revealed an overall increase in sea level. The sea level in Chile does not strictly follow the global trend of the past two decades (similar to 3 mm year(-1)), but rather a slight agreement (from 1.2 to 0.6 mm year-(1)) from Arica up to Puerto Montt approximately, with the exception of PTAR and PWIL TGs, where we found a decrease of-0.9 and-0.8 mm year(-1), respectively.