The acidification of the world's oceans—literally, becoming more acidic—is a concerning trend that's closely watched by scientists. Indeed, acidification kills wildlife and has been implicated in past mass extinctions on Earth. In a new study, scientists have found that acidification in the western Arctic Ocean is occurring at a rate three to four times higher than in other oceans due to climate change—a finding that could spell trouble for global oceans as well.
This study found that the Arctic Ocean’s acidification rate is correlated to the speed of sea-ice loss, which is driven by climate change. The Arctic Ocean’s rapidly melting sea ice results in waters that are more exposed to the atmosphere and thus more easily absorb the air’s increased levels of carbon dioxide, which causes acidification. Scientists say that if sea ice continues to melt at its current rate, the rapid acidification of the ocean will intensify in the next few decades until there is no sea ice left in the Arctic Ocean. When carbon dioxide dissolves in seawater, it becomes carbonic acid, which dissociates into hydrogen and bicarbonate ions. The addition of excess hydrogen ions lowers the ocean’s pH level, which means it becomes more acidic and harms organisms sensitive to acidity. The increase in bicarbonate ions reduces the amount of carbonate in water, which affects marine organisms such as coral whose exoskeletons are made of carbonate combined with calcium.
In addition to weakening coral reefs, acidification is killing sea snails in the Pacific and the biggest extinction event in planetary history, known as The Great Extinction, was potentially caused by ocean acidification. The new study, written by scientists Wei-Jun Cai—the Chair of Earth, Ocean, and Environment Studies at the University of Delaware—and Liqi Chen, a professor at China's Third Institute of Oceanography, focuses on acidification’s impact specifically on the Arctic’s ecosystem using rates measured between 1994 and 2020. “Ocean acidification is really more than just how that affects the carbonate-building organisms,” Cai told Motherboard. “There are a bunch of chemical processes in the ecosystem that will all be affected." For example, he said, some toxic trace metals could be more widespread with a lower pH level. "Our study will bring some attention [to the fact] that people need to really look at Arctic acidification as a consequence on the biological system," Cai said. The consequences of the rapid acidification of the Arctic Ocean will be felt globally because it flows into both the Pacific and the Atlantic oceans. The Arctic’s disproportionately high acidification also helps magnify the impact of carbon dioxide on all of our oceans, which will likely face a similar fate.
According to Cai, the rapid rate of acidification in the Arctic could "showcase what the lower latitude oceans may be for the future."
The study's co-authors discovered the role of sea ice loss in acidification because they found that when the ocean’s ice begins to melt in the spring, the carbon dioxide under the ice is lower than the amount in the atmosphere. But by the time the ice melts completely in the summer, the amount of carbon dioxide in the surface waters nearly matches the amount in the atmosphere. This shows that the carbon dioxide increase in the water occurs when ice is unable to create a barrier between the water and the atmosphere. The freshwater from ice that mixes with ocean water also decreases the seawater’s alkalinity, which is the ability for water to resist acidification. Cai pointed to the human impact that is driving ice-melt and acidification rates, specifically citing the “human use of fossil fuels and deforestation and cement production” to Motherboard. “The ultimate solution would be to remove fossil fuels from the atmosphere, to reduce the emissions, and also try to remove CO2 activity from the atmosphere,” Cai said. One way to do this, he says, is through Carbon Dioxide Removal (CDR), which includes reforestation, soil carbon sequestration, and ocean-based CDR like seaweed farming. CDR, however, does not directly address fossil fuels or industrial emissions. “The rate of warming in the Arctic is twice the global average, so the melting is very dramatic and we see [that] the rate of acidification is very much regulated by the ice-melt rate. So reducing global warming, reducing CO2 emissions looks the way to go,” Cai said.
Sign up for Motherboard’s daily newsletter for a regular dose of our original reporting, plus behind-the-scenes content about our biggest stories.