Understanding Sea Level Change in the South Pacific During the Late 20th Century and Early 21st Century

Abstract

A spatially nonuniform sea level rise was observed in the South Pacific with high trends of up to 8 mm/year in the southwest subtropical Pacific and much lower values in the eastern ocean during the 1993 to 2015 altimetry data period. Negative trends were observed further south. In recent decades, these trends have been interpreted as a spin-up of subtropical gyre circulation. Here an analysis of altimetry data and data from the Coupled Model Intercomparison Project Phase 5 is presented, which attempts to separate natural climate variability from sea level changes. In order to quantify the impact of natural variability, a multiple linear regression was performed between sea level and dominant climate indices in the region, with the latter representing interannual to interdecadal climate variability. Our results indicate that the observed pattern cannot completely be explained by the climate modes but that a large residual trend remains.