It’s no secret that sea levels along the East Coast of the United States are rising. But what’s less known is that the water isn’t rising at the same rate everywhere. As the climate continues to change, some cities may remain dry while others struggle to keep water out.
During the 20th century, sea levels rose about 18 inches near Cape Hatteras in North Carolina and along the Chesapeake Bay in Virginia. During that same time period, New York City and Miami experienced a 12 inch sea level rise, while the waters near Portland, Maine only rose 6 inches. According to a study recently published in the journal Nature, there’s an explanation for this.
The variation is a result of a phenomenon called “post-glacial rebound.” During the last ice age, huge sheets of ice once covered land areas in the Northern Hemisphere, including parts of the Northeast U.S. The weight of the ice weighted down the land like a boulder on a trampoline. At the same time, peripheral lands such as the U.S. mid-Atlantic coast rose up. As the ice melted, the previously weighted-down regions rebounded while the peripheral lands began to sink. While these ice sheets disappeared some 7,000 years ago, this see-sawing of post-glacial rebound continues to this day.
Researchers combined data from GPS satellites, tide gauges, and fossils in sediment with complex geophysical models to produce this comprehensive view of sea level change since 1900. While post-glacial rebound accounts for most of the sea level variation along the East Coast, researchers noted that when that factor is stripped away, “sea level trends increased steadily from Maine all the way down to Florida.”
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Why is sea level rising faster in some places along the US East Coast than others?
Photo, posted August 24, 2014, courtesy of Bill Dickinson via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio.
