Sea level rise will affect each area of the planet in a unique way, but new projections are helping researchers and lawmakers in Washington state identify which coastal communities are most vulnerable.
A new report published earlier this month by the National Oceanic and Atmospheric Administration says sea levels will rise 10 to 12 inches in the contiguous U.S. by 2050 — with regional variations — which scientists say would trigger a “profound increase” in coastal flooding.
The Washington coast could see as much sea level rise — 4 to 6 inches — in the next three decades as it did in the previous century.
By the end of the century, the state could see nearly 3 feet in average sea level rise, according to the new projections, a jump from 2 feet in past studies.
The state has many vulnerable places, including coastal and low-lying areas in and around Neah Bay, Port Angeles, Seattle and Cherry Point.
The new report is “sobering,” King County Climate Preparedness Program Manager Lara Whitely Binder said in an email.
The NOAA report “reaffirms the importance of planning for sea level rise in King County,” she said. “The new report increases my confidence that we are planning for the right amount of sea level rise — based on what we know now.”
According to projections from 2018 by the Washington Coastal Resilience Project, King County is expecting 2 to 3 feet of sea level rise — and up to 5 feet — by 2100.
While the East and Gulf coasts are expected to see the most sea level rise, experts say the preparedness of coastal communities — not so much the amount or frequency of environmental change — will determine how much damage they suffer.
“The impacts associated with sea level rise in a coastal community, and the vulnerability of a coastal community to those impacts, aren’t directly tied to the magnitude of change,” said Ian Miller, a coastal hazards specialist with Washington Sea Grant of the University of Washington.
Miller works with coastal communities on the Olympic Peninsula to help them prepare for tsunamis, erosion, flooding and other natural risks exacerbated by climate change.
“What this [NOAA] report doesn’t do is evaluate the impacts of 9 inches of sea level rise here versus 15 on the Gulf Coast,” he said. “It’s not inconceivable that the impacts we may experience might be more despite the fact that the sea level rise we’re seeing is less.”
Depending on topography, ocean behavior and infrastructure, increases in sea level can lead to increases in flooding, storm surges, permanent submergence of low-lying areas, erosion, saltwater corrosion and habitat loss.
Seattle has seen more than 9 inches in sea level rise since 1899 based on measurements by a NOAA tide gauge located at Colman Dock, according to King County.
The new report estimates it will see about that much rise by 2050.
While variables make it difficult to predict exactly how much levels will rise, especially past 2050, improvements in technology and sampling data will help scientists narrow down the margin of possible scenarios.
The local impacts of rising seas are many.
Previous reports predicted an uptick in flooding across low-lying areas in Seattle, Tacoma and Olympia. In addition, nearly 70% of Washington’s tidal wetlands could disappear by 2100 and historic flooding that has occurred every century could become more frequent and more devastating.
In 2020, King County updated its comprehensive plan to establish a sea level rise risk area on Vashon and Maury islands.
Washington lawmakers are urging for more.
“Coastal communities in Washington state are extremely vulnerable to sea level rise and coastal hazards and that’s why we must continue to push forward to help communities construct climate resilient infrastructure and habitat,” Sen. Maria Cantwell. D-Wash., said in a statement. “We have to ensure that our coastal communities have the tools and resources to prepare and adapt to climate change and sea level rise.”
NOAA pushes for local changes
The damage caused by a rising sea will be costly, said Nicole LeBoeuf, director of NOAA’s National Ocean Service, adding that 40% of U.S. residents live along the coast.
“By 2050, the expected relative sea level will cause tide and storm surge heights to increase and will lead to a shift in U.S. coastal flood regimes, with major and moderate high tide flood events occurring as frequently as moderate and minor high tide flood events occur today,” the report states. “Without additional risk-reduction measures, U.S. coastal infrastructure, communities, and ecosystems will face significant consequences.”
And yet, scientists believe the worst won’t come until after 2100 when glacial melting near Antarctica and Greenland are predicted to begin affecting long-term sea level rise.
Estimates in the report, however, are “driven by uncertainty in future emissions pathways and the response of the underlying physical processes.”
The research led by NOAA provided a current projection of expected sea level rise — in relation to sea level in 2000 — in the U.S. coastline for every decade until 2150.
“This is a global wake-up call and gives Americans the information needed to act now to best position ourselves for the future,” NOAA Administrator Rick Spinrad said. “These updated data can inform coastal communities and others about current and future vulnerabilities in the face of climate change and help them make smart decisions to keep people and property safe over the long run.”
NASA’s Sea Level Change Team helped create the updated report by building upon a 2017 study using data from the Sixth Assessment Report of the United Nations Intergovernmental Panel on Climate Change released in August 2021.
Still, many things remain uncertain. The disintegration of ice shelves, ground uplift and the trajectory of greenhouse gas emissions over the next several decades, among many other things, will largely determine sea level rise.
The elephant in the room, said Guillaume Mauger of the UW Climate Impacts Group, is when, how and to what degree glaciers in Antarctica and Greenland melt.
While sea level rise until 2050 is effectively locked in because of past emissions, what happens after that will be influenced by efforts to reduce carbon emissions.
“Even if we could magically turn off greenhouse gases tomorrow, we’re kind of stuck with what we’re going to get by 2050,” Mauger said. “What we see at the end of the century … is strongly dependent on how much we emit between now and then.”