June 17, 2013

The Reconstructed Sea Level dataset contains sea level anomalies derived from satellite altimetry and tide gauges.  Since 1993, satellite altimetry has provided accurate measurements of sea surface height with near-global coverage. These measurements led to the first definitive estimates of global mean sea level (GMSL) rise and have improved understanding of how sea levels are changing regionally at decadal time scales These relatively short records, however, provide no information about the state of the ocean prior to 1993, and with the modern altimetry record spanning only 20 years, the lower-frequency signals that are known to be present in the ocean are difficult or impossible to resolve. Tide gauges, on the other hand, have measured sea level over the last 200 years, with some records extending back to 1807. While providing longer records, the spatial resolution of tide gauge sampling is poor, making studies of the large-scale patterns of ocean variability and estimates of GMSL difficult. Combining the satellite altimetry with the tide gauges using a technique known as sea level reconstruction results in a dataset with the record length of the tide gauges and the near-global coverage of satellite altimetry.

The data can be obtained through the following methods:
  •  PO.DAAC Drive:  podaac-tools.jpl.nasa.gov/drive/files/allData/recon_sea_level/preview/L4/tg_recon_sea_level
  •  OPeNDAP:  opendap.jpl.nasa.gov/opendap/SeaSurfaceTopography/recon_sea_level/preview/L4/tg_recon_sea_level/contents.html
Read software and a dataset user guide can be found at:
  • Read Software: podaac-tools.jpl.nasa.gov/drive/files/allData/recon_sea_level/preview/L4/tg_recon_sea_level/sw
  • User Guide:  podaac-tools.jpl.nasa.gov/drive/files/allData/recon_sea_level/preview/L4/tg_recon_sea_level/docs

Cyclostationary empirical orthogonal functions (CSEOFs), derived from satellite altimetry, are combined with historical sea level measurements from tide gauges to create the Reconstructed Sea Level dataset spanning from 1950 through 2009. Previous sea level reconstructions have utilized empirical orthogonal functions (EOFs) as basis functions, but by using CSEOFs and by addressing other aspects of the reconstruction procedure, an alternative sea level reconstruction can be computed.  For specific information on the algorithm and how the CSEOFs are applied to the tide gauge data please see Hamlington, B. D., R. R. Leben, R. S. Nerem, W. Han, and K.-Y. Kim (2011), Reconstructing sea level using cyclostationary empirical orthogonal functions, Journal of Geophysical Research, 116, C12015, doi:10.1029/2011JC007529.

The data are provided on 0.5 degree grids with a 7 day temporal resolution.  The data are in NetCDF, and each file contains approximately 10 years worth of data.  There will be periodic updates that will extend the time series.

For more information please visit the dataset information page at:


Figure 1.:  SSHA from 3 January 1950
Figure 2.:  SSHA from 27 June 2009
Figure 3.:  Global mean sea level anomaly smoothed over 1 year.  The light blue line is the trend of sea level change from 3 January 1950 – 2 January 1986, green line is the trend from 3 January 1986 – 27 June 2009 and the dark blue line is the trend for the entire time series.