Warmer climate causing acidification of the Arctic Ocean

As early as the expedition in 2014 with the icebreaker Oden, the researchers could see that the sea ice coverage was greatly reduced in the Arctic. Photo: Jorien Vonk

By comparing data from a long list of Arctic expeditions, researchers have been able to see how the pH of the ocean north of Alaska and Siberia has decreased rapidly. In recent decades, the rate of acidification of the Arctic Ocean has been 3–4 times faster than in other oceans. This is because more carbon dioxide is taken up by the sea water when the surface is in direct contact with the atmosphere without a barrier of ice. In the past, the sea ice has kept the sea water close to the North Pole from being saturated with carbon dioxide.

“The time-series of pH measurements made in the Arctic Ocean is long. The oldest are from an expedition in 1994, when the ice sheet was extensive and thick, and measurements were taken in the leads between the ice floes. On the expedition in 2014, the icebreaker Oden was able to travel in open water half way from Siberia to the North Pole,” says Leif Anderson, researcher in marine chemistry at the University of Gothenburg and one of the authors of the study.

The measured acidification over the last 30 years corresponds to about 0.1 on the pH scale. The researchers estimate that the pH value will decrease a further 0.3 by the next turn of the century if carbon dioxide levels continue to rise in the atmosphere as they are today. The impact will be greatest in the coldest oceans. Water temperature determines how much carbon dioxide can be dissolved in the ocean. More freshwater from melted sea ice also result in a larger acidification effect by the uptake of carbon dioxide from the atmosphere due to changes in the seawater chemistry.

Article in Science: Climate change drives rapid decadal acidification in the Arctic Ocean from 1994 to 2020

Leif Anderson, University of Gothenburg, 19 October 2022. Press release.

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