Analysis of interannual and low-frequency variability in global mean sea level from altimetry and tide gauges

Abstract

Interannual and low frequency variations in global mean sea level (GMSL) are studied for the period 1950–1998 by interpolating sparse tide gauge data to a global grid using empirical orthogonal functions of sea level variability determined from TOPEX/Poseidon altimeter data. Results are based on data with long-term trends removed. The fact that the results do not have secular trends is an artifact of the analysis, and should not be interpreted as an indication that sea level is not rising. An error assessment based on comparing the reconstructed GMSL time series with other measurements suggests the accuracy of the time series is 2–4 mm. The GMSL from 1950 to 1998 is shown to be significantly correlated with El Niño/La Niña events for periods of 1–5 years if the GMSL is lagged by 3 months. GMSL at periods longer than 5 years is significantly correlated with the Pacific Decadal Oscillation if GMSL is lagged by 5 months. A wavelet analysis of the GMSL suggests a shift from dominant interannual variations at 2–3 year periods in the early record to 4–6 year periods in the later part of the record.