Atolls and other low-lying islands in the Pacific Ocean may not slip under the waves but they will likely become uninhabitable due to overwashing waves

By Julia Pyper and ClimateWire

U.S. protectorates like the Republic of the Marshall Islands and the Federated States of Micronesia can also expect to become increasingly uninhabitable. Pictured: Kwajalein Atoll, Marshall Islands. Image: Flickr/Matt Kieffer

As ice caps melt and sea levels rise, islands around the world could eventually become completely submerged, like real-world cities of Atlantis.

Scientists have determined that the tides could consume low-lying islands in the next 50 to 150 years. But they'll become uninhabitable well before they're underwater, and that day might not be in the too distant future.

A study by the U.S. Geological Survey released yesterday finds that the two northwestern Hawaiian atolls of Midway and Laysan and Pacific islands like them could become inundated and unfit to live on during this century.

A fierce storm in 2008 drew researchers' attention to the issue of overwash, where ocean water comes ashore, damages property and natural resources but doesn't permanently submerge the island. On islands that are less than a thousand feet long and where fresh water turns brackish less than a dozen feet deep, overwash can have a crippling effect.

"If you have an overwash event, all of a sudden, you're salinating that fresh water; you basically kill the agriculture due to salt loading, and if you get [salt concentrations] over a few parts per thousand, it's no longer fit for human consumption," said Curt Storlazzi, a research oceanographer at the USGS Pacific Coastal and Marine Science Center and lead author of the study.

"You may have an island, but without fresh water and agriculture, you can't live there, anyway," he added. "It's like, do you care that in 100 years your house will be underwater? Or do you care that in 20 or 30 years ocean water is going to come through the side of your house a couple times every year?"

Not drowned, but uninhabitable To measure sea-level rise, scientists have historically used passive "bathtub" models that flood a given area in a concentric range. To better understand the effects of overwash, USGS used dynamic modeling that takes into account storm winds and wave activity coupled with sea-level rise of between 0.5 and 2 meters (1.6 and 6.5 feet).

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Storm Surges, Rising Seas Could Doom Pacific Islands This Century