One byproduct of rising carbon-dioxide levels is increasing ocean acidity — a phenomenon that scientists have termed an existential threat to marine life. The waters of the Arctic and the far-north Pacific are particularly prone to acidification as a result of several natural factors, so scientists regard the region as the proverbial canary in the coal mine for the rest of the world's oceans. A new study shows that within just fifteen years these waters may be too acidic for a range of marine animals to build and maintain their shells year round.

One byproduct of rising carbon-dioxide levels is increasing ocean acidity — a phenomenon that scientists have termed an existential threat to marine life. The waters of the Arctic and the far-north Pacific are particularly prone to acidification as a result of several natural factors, so scientists regard the region as the proverbial canary in the coal mine for the rest of the world's oceans. A new study shows that within just fifteen years these waters may be too acidic for a range of marine animals to build and maintain their shells year round.

Ocean acidification works like this: The top layer of the ocean comes into contact with atmospheric gases, gradually dissolving them. Carbon dioxide forms carbonic acid when dissolved in water, increasing the ocean's acidity. As ocean water acidifies, it eventually loses its ability to maintain levels of calcium carbonate minerals that many marine organisms, from tiny plankton at the bottom of the food chain to clams and crabs, require to build their shells.

The new study, published in the journal Oceanography, notes that already, "[t]he rapid accumulation of carbon dioxide in the upper thousand meters of the ocean has fundamentally altered the chemistry of seawater, making the ocean on average ~30% more acidic."

To identify how long it would take for Pacific-Arctic waters to reach critical thresholds beyond which shelled animals would not be able to reproduce or survive, researchers from the US National Oceanic and Atmospheric Administration (NOAA), the University of Alaska Fairbanks, and Woods Hole Oceanographic Institution spent a month on the US Coast Guard cutter Healy in the Bering, Chukchi, and Beaufort Seas off Alaska.

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Arctic ocean image via Shutterstock.