Global vs. Local Sea Level



Rising global sea level is one of the most commonly cited consequences of climate change, but it’s often unclear how it might affect people living on the coasts. 

First, let’s take a look at why sea level changes.  A rise in global sea level occurs due to the warming of the ocean and the addition of fresh water into the ocean basins from melting ice on land. Local sea level, known as relative sea level change, is affected by global sea level fluctuations, changes in land elevation, winds, and ocean circulation.

Satellite data indicates that since 1992, there has been an average rise of about 3 millimeters per year in global sea level.  That may not sound like much, but it adds up quickly.  And remember – sea level rise isn’t uniform across the globe. For instance, tide gauge measurements show that sea level is rising almost 10 mm/yr in Louisiana because the land is sinking. In other coastal areas, sea level trends are falling. For example, in southeast Alaska, local sea level trends are falling up to 17 mm/yr because the land is rising.

What do all these numbers mean?  Well, NOAA’s Sea Level Rise & Coastal Flooding Impacts Viewer gives a visual representation of how U.S. coastlines could be impacted by sea level rise, from current sea level to up to six feet higher.  This tool also shows areas currently subject to coastal flooding, as well as projected frequency and duration of flood events at hypothetical sea level rise scenarios.

Additionally, it also incorporates social and economic data to give a general idea of how vulnerable populations and local economies might be affected by sea level rise.

You can go online and use this tool to see how your area might be affected.

NOAA will continue to enhance its products and services to provide critical information on local and global sea level trends as we monitor the effects of climate change on our planet.