FAQ
What is MSL?
Mean Sea Level (MSL) is the average water level over a 19-year tidal epoch. Current measurements reference the 1983-2001 National Tidal Datum Epoch.
How often is data updated?
NOAA stations report water level every 6 minutes, typically available within an hour. Our cache refreshes every 5 minutes.
What causes sea level variation?
Tides (gravitational), storm surges (wind/pressure), seasonal thermal expansion, and long-term sea level rise. Local factors include land subsidence and coastal engineering.
How much has sea level risen?
Global mean sea level has risen about 21 cm since 1880. The current rate is approximately 3.6 mm/year and accelerating.