NOAA and partners develop new regional sea level scenarios to help U.S. communities prepare for risks

The National Oceanic and Atmospheric Administration (NOAA) and its partners have developed new regional sea level scenarios for the United States to give coastal communities better and more localized data to help them plan for and adapt to the risks of rising sea levels to their economies and infrastructure.

Sea level rise is occurring worldwide, but not at the same rate everywhere, NOAA noted in a statement on Thursday. “Differences will also likely continue in the future, so decision-makers need local information to assess their community’s vulnerability,” the statement said. “These new scenarios integrate updated global sea level rise scenarios with regional factors, such as changes in land elevations and ocean circulation, that influence sea level regionally.”

William Sweet, a NOAA oceanographer and lead author of the report detailing the scenarios, explained that the “ocean is not rising like water would in a bathtub. For example, in some scenarios sea levels in the Pacific Northwest are expected to rise slower than the global average, but in the Northeast they are expected to rise faster. These scenarios will help communities better understand local trends and make decisions about adaptation that are best for them.”

In the report, titled Global and Regional Sea Level Rise Scenarios for the United States, the researchers relied on the “latest published and peer reviewed science” to refine six global sea level rise scenarios (low, intermediate low, intermediate, intermediate high, high, and extreme) decade by decade for this century. The report helps communities track a range of scenarios that they may fall under for each of the timeframes, and assess their risk of experiencing impacts under the scenario. The researchers scaled these scenarios down to a one-degree gridded resolution, or roughly 70 miles. “This allows a coastal manager in Miami and one in Mobile, Alabama, using the same scenario to prepare for different outcomes,” the statement explained.

Among the report’s key findings:

• Along regions of the Northeast Atlantic (Virginia coast and northward) and the western Gulf of Mexico coasts, relative sea level (RSL) is projected to be greater than the global average for almost all future global mean sea level (GMSL) rise scenarios (for example, 0.3-0.5 metres or more RSL rise by the year 2100 than GMSL rise under the intermediate scenario);
• Along much of the Pacific Northwest and Alaska coasts, RSL is projected to be less than the global average under the low-to-intermediate scenarios (e.g. 0.1-1 metre or less RSL rise by the year 2100 than GMSL rise under the intermediate scenario); and
• Along almost all U.S. coasts outside Alaska, RSL is projected to be higher than the global average under the intermediate high, high and extreme scenarios (e.g. 0.3-1 metre or more RSL rise by the year 2100 than GMSL rise under the high scenario).

NOAA added in the statement that a similar method is already being used in state planning in the mid-Atlantic and Gulf of Mexico and has been previously used to assess risk to worldwide U.S. military installations in an interagency report prepared for the U.S. Department of Defense in 2016.

A joint public- and private-sector group developed the report for the Sea Level Rise and Coastal Flood Hazard Scenarios and Tools Interagency Task Force, which was convened by the U.S. Global Change Research Program and National Ocean Council in 2015. Researchers from NOAA, Rutgers University, the Environmental Protection Agency, South Florida Water Management District, Columbia University, and U.S. Geological Survey co-authored the report.