Sea Level Rise Will Affect Major US Cities

New research which has focused solely on the continental United States of America has found that by 2100, 9 percent of the land within 180 coastal cities could be threatened by rising sea levels.

Such a rise means that the Gulf and southern Atlantic coasts would be particularly hard hit, seeing cities like Miami, New Orleans, Tampa and Virginia Beach losing 10 percent of their land area by 2100.

This is the first analysis that looks at every coastal city in the lower 48 states with a population of 50,000 or more, and one of the most detailed studies, using data that allowed the researchers to view into very high resolution images of coastal regions.

Current scientific predictions indicate that by 2100 the ocean levels will have risen about 1 meter, and could see continuing sea level rise of a meter per century if the current rate of global warming continues apace.

“According to the most recent sea-level-rise science, that’s where we’re heading,” said lead researcher Jeremy L. Weiss, a senior research specialist in the UA’s department of geosciences. “Impacts from sea-level rise could be erosion, temporary flooding and permanent inundation.”

“With the current rate of greenhouse gas emissions, the projections are that the global average temperature will be 8 degrees Fahrenheit warmer than present by 2100,” said Weiss, who is also a UA doctoral candidate in geosciences.

“That amount of warming will likely lock us into at least 4 to 6 meters of sea-level rise in subsequent centuries, because parts of the Greenland and Antarctic ice sheets will slowly melt away like a block of ice on the sidewalk in the summertime.”

“Our work should help people plan with more certainty and to make decisions about what level of sea-level rise, and by implication, what level of global warming, is acceptable to their communities and neighbors,” said co-author Jonathan T. Overpeck, a UA professor of geosciences and of atmospheric sciences and co-director of UA’s Institute of the Environment.

Weiss, Overpeck, and others, looked at how much land area from the 180 municipalities could be affected if the sea levels rose 1 to 6 meters. At 3 meters (almost 10 feet), on average more than 20 percent of land in those cities could be affected. Nine large cities, including Boston and New York, would have more than 10 percent of their current land area threatened. By 6 meters (about 20 feet), about one-third of the land area in U.S. coastal cities could be affected.

“Ours is the first national-scale data set that delineates these low-lying coastal areas for the entire lower 48 at this degree of spatial resolution,” Weiss said.

The NED data set has some uncertainty, particularly for estimating elevation changes of 1 meter or less. That means the researchers’ ability to identify the threat to any particular small piece of land is better for larger amounts of sea-level rise than for smaller amounts of sea-level rise, Weiss said.

“As better digital elevation models become available, we’ll be using those,” Weiss said. “The USGS is always improving the digital elevation models for the U.S.”

Overpeck said, “The main point of our work is to give people in our coastal towns and cities more information to work with as they decide how to deal with the growing problem of sea-level rise.”

Source: The University of Arizona

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