An international team of researchers found that ocean acidification is spreading quickly in the western Arctic Ocean. The findings have been published in the Nature Climate Change.
It turns out that acidified waters spread northward or 300 nautical miles from the Chukchi slope off the coast of northwestern Alaska to the North Pole between the 1990s and 2010. Meanwhile, the depth has worsened from 325 feet to 800 feet.
“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,” said study co-author Richard Feely, NOAA senior scientist.
Sea snails called pteropods are an essential part of the food web in the Arctic and they could be affected by ocean acidification. It their population declines, its effects will be felt in the larger marine ecosystem. Shrimp, crabs and salmons would also get affected.
The team, which also included researchers from Sweden and China, took water samples in the upper ocean of the Arctic, just below the North Pole. This was done in the summer of 2008 and 2010.
They measured dissolved inorganic carbon and alkalinity in the samples. This allowed them to determine the pH and the saturation state for aragonite, which is a carbonate mineral that marine organisms use to create their shells.
The researchers realized that the expansion of ocean acidification was largely because of the increased Pacific Winter Water (PWW) brought by circulation patterns and retreating sea ice during the summer. PWW is from the Pacific Ocean, which is high in carbon dioxide and more acidic. As it moves, it also absorbs more carbon from dead organisms in the sediments and water.
Due to the melting of Arctic sea ice during the summer, PWW has been permitted to travel further north. Previously, the ice melt during the summer was only found at depths no more than 200 meters but now, it became worse.
“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,” added University of Delaware professor Wei-Jun 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.”