(1 - 2 of 2)
- Estimating rates of acceleration based on the 157-year record of sea level from San Francisco, California, U.S.A.
- Breaker, L.C. and Ruzmaikin, A., 2013. Estimating rates of acceleration based on the 157-year record of sea level from San Francisco, California, U.S.A. The question of the acceleration of global sea level rise has gained increasing attention because the present rate of sea level rise is relatively small in comparison to the rates that are predicted to occur in the near future. Recent measurements have come under scrutiny on how to correctly analyze and interpret regional estimates of acceleration. In this context, we employ the Ensemble Empirical Mode Decomposition (EEMD), a data-adaptive method developed for the analysis of nonstationary and nonlinear data to estimate acceleration over the 157-year record of sea level from San Francisco, California. We define sea level acceleration (SLA) as the mean of the second differences of the residual from an EEMD. Using the residual provides a means by which to reduce or eliminate the contaminating influence of decadal and longer-period oscillations in sea level that are folded into estimates obtained using the conventional approach. For the entire record, a value of +0.011 ± 0.003 mm/y2 was obtained for the acceleration and its uncertainty, compared with +0.013 mm/y2, using the conventional approach. The effect of record length is examined by estimating the accelerations for truncated versions of the record, one starting in 1900 and a second in 1925. The accelerations differed in each case from the conventional values, as expected, because the methods are based on different definitions of SLA. © Coastal Education & Research Foundation 2013., Cited By (since 1996):1, Oceanography, CODEN: JCRSE
- Breaker, Ruzmaikin
- The 154-year record of sea level at San Francisco: Extracting the long-term trend, recent changes, and other tidbits,
- A data adaptive method called ensemble empirical mode decomposition (EEMD) is used to examine the 154-year record of monthly sea level at San Francisco. The mode that is lowest in frequency corresponds to the long-term trend. The next highest mode corresponds to an oscillation with a period of ~100 years and may be related to solar variability. When this mode is combined with the long-term trend, the rate of increase in sea level starts to decrease by ~1980. The next lower mode corresponds to interdecadal time scales and thus includes the Pacific Decadal Oscillation. When combined with the two lower modes, sea level itself starts to decrease by the mid-1990s. These results are consistent with the most recent results from the intergovernmental panel on climate change (IPCC), and may be the first obtained from a tidal record. Prior to conducting EEMD, corrections for glacial isostatic adjustment (GIA) and the inverse barometer (IB) effect were applied. The effect of applying the GIA correction was relatively small, but the IB correction reduced the slope of the long-term trend in sea level by almost 15%. This reduction is due to a long-term increase in the variance of sea level pressure. To determine if the 10-15 year ENSO modulation cycle could be detected from the decomposition we first compared the envelope from the mode associated with ENSO, with the two adjacent modes that were lower in frequency. Spectral analysis revealed no significant maxima in the ENSO mode envelope, but a major peak in the spectrum for the two adjacent modes, with a period of 12. 8 years. This is consistent with a local response to El Niño warming for the ENSO mode, but a non-local response for the two adjacent modes. A similar analysis was performed for the Southern Oscillation Index and a spectral maximum was found between 12 and 16 years, consistent with our non-local interpretation of the previous two modes. © 2010 Springer-Verlag., Cited By (since 1996):5, Oceanography, ,
- Breaker, Ruzmaikin