Monthly Steric Sea Level Grids
Sea level rises and falls as the temperature and salinity of the water column varies, which is known as steric sea level. Sea level also changes as the wind and ocean currents redistribute water mass within the ocean, or as water is added by precipitation, ice melting, or river runoff, or it is removed by evaporation or conversion to ice. Satellite radar altimeters such as TOPEX/POSEIDON and JASON-1 measure the combination of both effects, while GRACE measures only the changes in gravity caused by local changes in water mass. Thus, altimetry and GRACE data can be combined in order to compute the steric sea level variations. This is an important quantity to study weather and climate: since the effect of temperature is the largest source of change in steric sea level, steric sea level to a large extent describes the heat content in the upper layers of the ocean, heat which is available to be returned to the atmosphere.
Steric Sea Level component for 2 Feb 2003, obtained by subtracting the GRACE mass estimate from the Jason-1 sea surface height estimate.
At present (5/2006) we have data between Feb 2003 and April 2005.
in jpeg format are available at ftp://podaac.jpl.nasa.gov/pub/tellus/steric/data.
These data were produced by Dr. Don Chambers, of the Center for Space Research, U. Texas-Austin. Details on the computation can be found here.
Units and format:
The data files are here. They are plain ASCII files, compressed with the widely available gzip algorithm.
- the units are cm of water thickness
- the grids have 360 longitudes (0.5 to 359.5 in 1 degree increments) and 134 latitudes (-65.5 to +65.5 in 1 degree increments). However, points with undefined values are not included in the table, so the number of points is lower than 360*134.
- The format is a simple ASCII list of longitude, latitude, value.
When using these data, please acknowledge this website, and cite:
Chambers, D.P., 2006: Observing seasonal steric sea level variations with GRACE and satellite altimetry. J. Geophys. Research, vol 111, C03010, doi:10.1029/2005JC002914
Also, please read the more detailed document linked above, under "Details on the computation", as it is has much useful material that cannot be easily included in a refereed publication.
LAST UPDATE: 2007-05-01 V.Zlotnicki