Climate: Researchers report startling rate of acidification in parts of the Arctic Ocean

‘Nowhere on Earth have we documented such large scale, rapid ocean acidification’

Researchers with the
Researchers with the NASA-funded ICESCAPE Mission explore freshwater melt ponds in the Arctic. Photo courtesy NASA Earth Observatory.

By Summit Voice

FRISCO — The steady decline of Arctic sea is speeding ocean acidification, researchers reported this week in PLoS One, describing their findings after extensive water sampling in the region.

“A remarkable 20 percent of the Canadian Basin has become more corrosive to carbonate minerals in an unprecedented short period of time. Nowhere on Earth have we documented such large scale, rapid ocean acidification,” said lead researcher and ocean acidification project chief, U.S. Geological Survey oceanographer Lisa Robbins.

The research showed that the rapid pace of sea ice decline may be contributing directly to increasing acidification by exposing more of the ocean to atmospheric carbon dioxide. The impacts are intensified further by the diluting effect of melting ice. The freshwater further lowers pH levels and reducing the concentrations of calcium and carbonate, which may impact the growth of organisms that many species rely on for food.

Ocean acidification occurs as seawater absorbs more carbon dioxide, causing a drop in the pH level, making the water more acidic. Numerous studies have shown that more acidic water makes it harder for many organisms to build their shells or skeletons. In some cases, the water is directly corrosive to shells, as shown by a recent British Antarctic Survey study that documented impacts to sea snails in the Southern Ocean around Antarctica. These changes, in species ranging from corals to shrimp, have the potential to impact species up and down the food web.

The new research shows that acidification in surface waters of the Arctic Ocean is rapidly expanding into areas that were previously isolated from contact with the atmosphere due to the former widespread ice cover.

Globally, Earth’s ocean surface is becoming acidified due to absorption of man-made carbon dioxide. Ocean acidification models show that with increasing atmospheric carbon dioxide, the Arctic Ocean will have crucially low concentrations of dissolved carbonate minerals, such as aragonite, in the next decade.

“In the Arctic, where multi-year sea ice has been receding, we see that the dilution of seawater with melted sea ice adds fuel to the fire of ocean acidification” said co-author and co-project chief, Jonathan Wynn, a geologist from the University of the South Florida. “Not only is the ice cover removed leaving the surface water exposed to man-made carbon dioxide, the surface layer of frigid waters is now fresher, and this means less calcium and carbonate ions are available for organisms.”

Researchers were able to investigate seawater chemistry at high spatial resolution during three years of research cruises in the Arctic, alongside joint U.S.-Canada research efforts aimed at mapping the seafloor as part of the U.S. Extended Continental Shelf program. In addition to the NOAA supported ECS ship time, the ocean acidification researchers were funded by the USGS, National Science Foundation, and National Oceanic and Atmospheric Administration.

Compared to other oceans, the Arctic Ocean has been rather lightly sampled.

“It’s a beautiful but challenging place to work,” said Robert Byrne, a USF marine chemist. Using new automated instruments, the scientists were able to make 34,000 water-chemistry measurements from the U.S. Coast Guard icebreaker. “This unusually large data set, in combination with earlier studies, not only documents remarkable changes in Arctic seawater chemistry but also provides a much-needed baseline against which future measurements can be compared.” Byrne credits scientists and engineers at the USF College of Marine Science with developing much of the new technology.


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