Ocean acidification is increasing at a rapid pace in the western Arctic Ocean — both with regard to area and also depth — new research from an international group of collaborators has found.
To be more specific, the researchers found that “between the 1990s and 2010, acidified waters expanded northward approximately 300 nautical miles from the Chukchi slope off the coast of northwestern Alaska to just below the North Pole.”
In addition, it was found that the depth of acidified water increased during this same period of time from around 325 feet to more than 800 feet (~100 meters to ~250 meters).
“The Arctic Ocean is the first ocean where we see such a rapid and large-scale increase in acidification, at least twice as fast as that observed in the Pacific or Atlantic oceans,” commented University of Delaware professor Wei-Jun Cai, the US lead principal investigator on the project.
A senior NOAA scientist who co-authored the new study by the name of Richard Feely noted: “The rapid spread of ocean acidification in the western Arctic has implications for marine life, particularly clams, mussels, and tiny sea snails that may have difficulty building or maintaining their shells in increasingly acidified waters.”
This matters because many of these animals, pteropod sea snails in particular, form the base of the region’s food chains/web. Salmon and herring fisheries, for instance, would very likely collapse with major changes to pteropod quantity and/or distribution. Crab fisheries, of course, would be directly affected.
The press release provides more:
The researchers studied water samples taken during cruises by Chinese ice breaker XueLong (meaning ‘snow dragon’) in summer 2008 and 2010 from the upper ocean of the Arctic’s marginal seas to the basins as far north as 88 degrees latitude, just below the North Pole, as well as data from three other cruises.
Scientists measured dissolved inorganic carbon and alkalinity which allows them to calculate pH and the saturation state for aragonite, a carbonate mineral that marine organisms need to build their shells.
Data collected by ship and model simulations suggest that increased Pacific Winter Water (PWW), driven by circulation patterns and retreating sea ice in the summer season, is primarily responsible for this OA expansion, according to Di Qi, the paper’s lead author and a doctoral student of Chen.
PWW comes from the Pacific Ocean through the Bering Strait and shelf of the Chukchi Sea and into the Arctic basin. In recent years, melting sea ice has allowed more of the Pacific water to flow through the Bering Strait into the Arctic Ocean. Pacific Ocean water is already high in carbon dioxide and has higher acidity. As the ocean mass moves north, it absorbs additional carbon dioxide from decomposing organic matter in the water and sediments, increasing acidity.
The melting and retreating of Arctic sea ice in the summer months also has allowed PWW to move further north than in the past when currents pushed it westward toward the Canadian archipelago.
Also, the meltwater from summer sea ice melting is now being found deeper and deeper than was the case previously.
“It’s like a melting pond floating on the Arctic Ocean. It’s a thin water mass that exchanges carbon dioxide rapidly with the atmosphere above, causing carbon dioxide and acidity to increase in the meltwater on top of the seawater,” explained Cai. “When the ice forms in winter, acidified waters below the ice become dense and sink down into the water column, spreading into deeper waters.”
So … the primary real-world implication of this work is that ocean acidification is looking fairly likely to cause a collapse of important Arctic fisheries within the lifetimes of those reading this (even if potential overfishing and growing levels of pollution weren’t looking likely to lead to a similar state of things).
The new research was published in the journal Nature Climate Change.
Images via University of Delaware
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