U.S. Could See a Century’s Worth of Sea Level Rise in Just 30 Years

The seas lapping against America’s coastlines are rising ever faster and will be 10 to 12 inches higher by the year 2050, with major Eastern cities hit regularly with costly floods even on sunny days, a government report says.

The National Oceanic and Atmospheric Administration and six other federal agencies issued a 111-page report Tuesday that warns of “significant consequences” from rising seas in the next few decades, with parts of Louisiana and Texas projected to see waters a foot and a half (0.45 meters) higher.

However, the worst of the long-term sea level rise from the melting of ice sheets in Antarctica and Greenland probably won’t kick in until after 2100, the study’s lead author said.
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Because of climate change, the nation’s coastlines on average will see as much sea level rise in the next 30 years as they did in the previous century, said lead author William Sweet, an oceanographer for NOAA’s National Ocean Service.

Warmer water expands and melting glaciers and ice sheet add more water to oceans around the globe.

The report “is the equivalent of NOAA sending a red flag up” about accelerating the rise in sea levels, said University of Wisconsin-Madison geoscientist Andrea Dutton, a specialist in sea level rise who wasn’t part of the federal report. The coastal flooding the U.S. is seeing now “will get taken to a whole new level in just a couple of decades.”

“We can see this freight train coming from more than a mile away,” Dutton said in an email. “The question is whether we continue to let houses slide into the ocean.”

Some areas see sea levels rise more than others due to sinking soil, currents, and water from melting ice. The United States will experience slightly higher sea levels than the global average. Sweet explained that the U.S. Coasts with the greatest sea level rise will be the Gulf and East Coasts. Hawaii’s West Coast and West Coasts will suffer a smaller increase than the average.

The report stated that between now 2060 and almost 25 inches (0.63 meters), sea level will rise nearly 2 inches (0.6 meters) in Galveston, Texas and less than 2 in St. Petersburg, Florida. It is just 9 inches (0.23 inch) in Seattle, but 14 inches (0.36 metres) in Los Angeles.

Higher seas can cause more damage to the coastline when hurricanes or other severe storms strike, but they’re becoming an issue even on sunny days.

Cities such as Miami Beach, Florida; Annapolis, Maryland; and Norfolk, Virginia, already get a few minor “nuisance” floods a year during high tides, but those will be replaced by several “moderate” floods a year by mid-century, ones that cause property damage, the researchers said.

“It’s going to be areas that haven’t been flooding that are starting to flood,” Sweet said in an interview. “Many of our major metropolitan areas on the East Coast are going to be increasingly at risk.”

The western Gulf of Mexico coast, should get hit the most with the highest sea level rise — 16 to 18 inches (0.4 to 0.45 meters) — by 2050, the report said. And that means more than 10 moderate property-damaging sunny-day floods and one “major” high tide flood event a year.

In the Gulf of Mexico, expect to see 14 to 16 inches (0.35 – 0.4 metres) of sea level increase by 2050. There will also be three light sunny-day floods each year. Mid-century should see the Southeast coast get between 0.3 and 0.35 meters of sea rise, four sunday-day moderate floods per year, and 10 to 10.5 inches for the Northeast coast (0.25 to0.3 meters) sea rise, and six mild sunny-day floods each year.

The Hawaiian Islands, Southwestern coast and Southwestern coast can expect 6-8 inches (0.15-0.2 meters) sea level rise before mid-century. Northwest coast will see only 4-6 inches (0.15-1.15 meters). While the Pacific coast will experience more than 10 sunshiny-day flooding incidents per year, it is only one of those that causes minor inconvenience and can be considered a moderate flood. Hawaii gets even less.

And that’s just until 2050. The report is projecting an average of about 2 feet of sea level rise in the United States—more in the East, less in the West—by the end of the century.


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