Rising sea levels, largely caused by climate change, could disrupt the lives of millions of Americans in the coming decades.
The U.S.'s extensive coastline, which is densely populated, will be vulnerable to more frequent and intense flooding, coastal erosion, and the loss of critical infrastructure.
These changes will profoundly impact American life—displacing communities, reshaping coastlines, and causing widespread economic disruption.
"Generally, sea levels are going up globally due to increased ocean temperature, which actually expands as it gets warmer, and then contributions from glaciers, mostly the big continental glaciers," Doug Marcy, a Senior Coastal Hazard Specialist with the National Oceanic and Atmospheric Administration's (NOAA) Office for Coastal Management told Newsweek.
"As we go farther out, CO2 emissions will become more and more important, if we reduce them or not," he explained.
Carbon dioxide emissions trap heat, which in turn causes oceans to warm and expand, ice sheets to melt, and sea levels to rise.
Sea level along the U.S. coastline is projected to rise, on average, around 10 to 12 inches by 2050, according to projections from NOAA. That's as much as the total rise measured over the entire last century, between 1920 and 2020.
The projections vary, based on how ice sheets will melt—whether gradually, or all at once—and most importantly, based on whether global emissions are reduced, Marcy said.
What sea level rise will look like
Not all states on the coastline will be impacted equally by sea level rise. Some areas will be hit harder due to what Marcy describes as a "double whammy" of rising sea levels combined with sinking land.
The sinking land problem, known as land subsidence, is particularly affecting states on the East Coast. It happens partly due to natural geological processes and also from human activities such as the extraction of groundwater from deep in the earth.
Overall, states on the East Coast and Gulf Coast are likely to be worst impacted by sea level rise, such as Florida, Virginia, North Carolina and Louisiana.
"People living on low-lying coastal land, like river mouths, are already facing higher flood risks because of the 20-40 cm [7.9—15.7 inches] of sea level rise measured along U.S. coasts over the past few decades. Their communities can expect the worst of the impacts as water levels continue to climb," Peter Girard, the spokesperson for nonprofit organization Climate Central, told Newsweek.
NOAA has created an interactive map, which uses projections to allow users to visualize how different parts of the United States would be affected if sea levels rose by various amounts.
As sea levels rise, the U.S.'s coast will slowly be inundated with water, with some low-lying areas becoming submerged entirely.
Nuisance flooding, also known as tidal flooding or sunny day flooding, will become typical. This refers to flooding that occurs even on clear days due to high tides exceeding normal levels.
Another thing that will happen is big storms will be worse. Higher water levels mean there will be higher storm surges, leading to more devastating coastal flooding during hurricanes and other major storms.
There are many other ways coastal areas could be affected. Groundwater table rise creates saltwater intrusion into lands which affects agriculture and makes it difficult to obtain clean drinking water. Rising water tables can also overwhelm wastewater systems, leading to potential health hazards.
Economic impact
Around 129 million people, or around 40 percent of the country's population, live in coastal areas, according to NOAA's Office for Coastal Management.
It also holds a significant percentage of the nation's economy. If the coastal counties were an individual country, it would rank third in the world in gross domestic product, behind the entire U.S. and China.
Rising sea levels will also have widespread economic impacts across the country, Margaret Walls, director of Climate Risks and Resilience Program at nonprofit Resources for the Future, told Newsweek.
This could be things as simple as local workers being unable to reach their place of work because of flooding, or retail businesses suffering if customers are unable to reach, along with the risks of damage to roads and buildings.
"It's not that businesses, especially big businesses, can't figure out a way to adapt. But there's all the folks who live and work in those locations who might not be able to still live and work in those locations. How are we going to deal with that?" Walls said.
Sea level rise could also lead to people being displaced and migrating within the country, which would have major impacts on the coastal economies they leave behind, as well as potentially putting pressure on infrastructure and social services where they migrate to.
Flood damage is also expensive. According to Girard of Climate Central, more than $8 billion of the flood damage caused by Hurricane Sandy in the New York area, which equates to roughly 13 percent of the total, could be attributed directly to sea level rise.
"Governments, businesses, and ultimately residents will be forced to pay increasingly higher costs to recover from disasters like this, and also to finance investments in coastal defenses and the protection of critical infrastructure, housing, and tourism economies," he said.
How the country is preparing
There are many ways in which states are adapting and preparing for sea level rise.
These preparations are very location specific, and include building sea walls, storm barriers and improving stormwater drainage systems. States have also elevated roads and critical infrastructure to make them more resilient to flooding, and implemented land-use planning strategies.
The adaptations are not cheap, and often will come at a cost to taxpayers.
The 2021 Bipartisan Infrastructure Law was touted by the White House as the "largest investment in the resilience of physical and natural systems in American history," investing more than $50 billion to protect against droughts, heat, and floods.
But one sea wall proposed to the New York-New Jersey Harbor Estuary from storm surges is estimated to cost $119 billion, highlighting the immense challenge of protecting the country's entire coastline with limited resources.
"In big cities, you know, we're not going to let New York City or Miami decline too much. There's too much at stake. So I think there'll be a lot of adaptation to keep those economies afloat," Walls said.
"In my opinion, I think the sort of smaller cities, smaller towns, the places where they don't have the resources to invest and they want to keep their economies viable, how is that going to happen?"
Another particular challenge will be for local governments to assess the risks and judge when and where to make adaptations.
For example, in some areas, the adaptations might simply be stopgap measures, as eventually sea levels will rise to the point that those adaptations are rendered obsolete.
"So do we invest? How much do we invest? When do we invest? And when do we retreat? Those are kind of really tricky kind of questions that I see as a kind of a timing/investment payoff kind of calculation that communities have to make," Walls said.
While sea level rise cannot be stopped, even in the most optimistic projections, it can be prepared for and possibly slowed.
"Ultimately, the only way to slow the rate of sea level rise is to cut carbon pollution. As long as the blanket of greenhouse gasses in our atmosphere grows thicker, global temperatures will climb and our oceans will rise in response," Girard said.
Newsweek