Reconstructing sea level using cyclostationary empirical orthogonal functions

Cyclostationary empirical orthogonal functions, derived from satellite altimetry, are combined with historical sea level measurements from tide gauges to reconstruct sea level fields from 1950 through 2009. Previous sea level reconstructions have utilized empirical orthogonal functions as basis functions, but by using cyclostationary empirical orthogonal functions and by addressing other aspects of the reconstruction procedure, an alternative sea level reconstruction can be computed. The procedure introduced here is capable of capturing the annual cycle and El Nino-Southern Oscillation (ENSO) signals back to 1950, with correlations between the reconstructed ENSO signal and common ENSO indices found to be over 0.9. The regional trends computed from the new reconstruction show good agreement with the trends obtained from the satellite altimetry, but some discrepancies are seen when comparing with previous sea level reconstructions over longer time periods. The computed rate of global mean sea level rise from the reconstructed time series is 1.97 mm/yr from 1950 to 2009 and 3.22 mm/yr from 1993 to 2009.