Surface waters in parts of the Arctic Ocean could become so acid that they could threaten the capability of marine animals to create and preserve their shells, scientists warn.

Such levels could occur by 2030 in the Chukchi and Beaufort Seas, and the Bering Sea could reach similar acidity levels by around 2045, researchers from NOAA, the Woods Hole Oceanographic Institution and the University of Alaska say.

"Our research shows that within 15 years, the chemistry of these waters may no longer be saturated with enough calcium carbonate for a number of animals from tiny sea snails to Alaska King crabs to construct and maintain their shells at certain times of the year," says NOAA oceanographer Jeremy Mathis, lead author of a study appearing in the journal Oceanography.

Because of its vulnerability to ocean acidification, the Pacific-Arctic region is providing early warning of the global effect of increased human-caused emissions of carbon dioxide, which are being absorbed by the world's oceans and causing them to become increasingly acidic, he explains.

"This change due to ocean acidification would not only affect shell-building animals but could ripple through the marine ecosystem," Mathis says.

Aboard a Coast Guard cutter conducting research cruises in 2011 and 2012, the researchers collected data on water temperatures, salinity and levels of dissolved carbon in the Bering, Beaufort and Chukchi Seas.

This allowed them to create a computer model to predict upcoming changes in the levels of calcium and carbonate ions that are dissolved in ocean waters, considered an important measure of ocean acidification.

Marine animals use a particular form of calcium carbonate known as aragonite to create their shells, but when concentrations of calcium and carbonate ions fall below certain levels, the aragonite-based shells can start to dissolve, especially in the early stages of life of marine animals, when the shells are newly-formed and often fragile, the researchers say.

Both shell-building creatures and the fish species that depend on them as a food source would likely be affected, they note.

That's a concern because the Pacific-Arctic region is one of the U.S.'s most valuable commercial fishery regions, with almost 60 percent of the nation's commercial fisheries haul by weight coming from Alaskan waters, NOAA says.

The continental shelf areas of the Chukchi, Beaufort and Bering Seas are particularly vulnerable to ocean acidification since, in addition to absorption of human-caused carbon dioxide emissions, glacial melting and upwelling of carbon-dioxide-rich deeper waters are also driving the phenomenon, the scientists say.

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