Relative Sea Level Trends
The sea level trends measured by tide gauges that are presented here are local relative sea level (RSL) trends as opposed to the global sea level trend. Tide gauge measurements are made with respect to a local fixed reference on land. RSL is a combination of the sea level rise and the local vertical land motion. The global sea level trend has been recorded by satellite altimeters since 1992 and the latest global trend can be obtained from NOAA's Laboratory for Satellite Altimetry, with maps of the regional variation in the trend. The University of Colorado's Sea Level Research Group compares global sea level rates calculated by different research organizations and discusses some of the issues involved.
| Relative Sea Level Trends mm/yr (feet/century) |
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 |
Above 9 (Above 3) |
 |
6 to 9 (2 to 3) |
 |
3 to 6 (1 to 2) |
 |
>0 to 3 (0 to 1) |
 |
-3 to 0 (-1 to 0) |
 |
-6 to -3 (-2 to -1) |
 |
-9 to -6 (-3 to -2) |
 |
Below -9 (Below -3) |
The Center for Operational Oceanographic Products and Services has been measuring sea level for over 150 years, with tide stations of the National Water Level Observation Network operating on all U.S. coasts. Changes in RSL, either a rise or fall, have been computed at 142 long-term water level stations using a minimum span of 30 years of observations at each location. These measurements have been averaged by month which removes the effect of higher frequency phenomena in order to compute an accurate linear sea level trend. The trend analysis has also been extended to 240 global tide stations using data from the Permanent Service for Mean Sea Level (PSMSL). This work is funded in partnership with the NOAA OAR Climate Observation Division.
Frequently Asked Questions:
What is Sea Level?
Why does Sea Level change over time?
What does Sea Level have to do with Climate?
What are the differences between historical and new sea Level trends and confidence intervals?
Data and Resources
- NOAA Technical Report NOS CO-OPS 86, "Patterns and Projections of High Tide Flooding Along the U.S. Coastline Using a Common Impact Threshold"
- NOAA Technical Report NOS CO-OPS 86, Data: Patterns and Projections of High Tide Flooding (CSV)
- NOAA Technical Report NOS CO-OPS 83, "Global and Regional SLR Scenarios for the U.S."
- NOAA Technical Report NOS CO-OPS 83, Data: Global and Regional SLR Scenarios for the U.S. (CSV)
- " Sea Level Rise " Sweet, et al. Climate Science Special Report: Fourth National Climate Assessment, Volume I
- "Incorporating Sea Level Change Scenarios at the Local Level" Marcy, D., et al., NOAA Coastal Services Center, 2012.
- NOAA Technical Report NOS CO-OPS 53, "Sea Level Variations of the United States 1854-2006"
- NOAA Technical Report NOS CO-OPS 36, "Sea Level Variations of the United States 1854-1999"