While global oceans have been exposed to rising CO2 levels in the atmosphere for several decades and thus began absorbing parts of that additional CO2 – leading to increasing ocean acidification, which among other effects has had a detrimental impact on coral reefs – sea ice had somewhat shielded the Arctic Ocean.
“We found that, under partially or newly ice-free conditions, [waters with low absorbed CO2] that were originally under the ice were exposed to higher atmospheric [CO2] and rapidly took up CO2 through air-sea gas exchange. In other words, the initial CO2 deficit resulted in a CO2 increase “boost” over that time period,” the study explains.
Leading to more absorption
In addition to acidification as the result of the protective “blanket” of sea ice being removed, the dilution of sea water with melting sea ice also further enhances the Arctic Ocean’s ability to absorb CO2. Sea ice that melts and enters the ocean reduces “the buffering capacity of the water” or its ability to resist acidification.
This results in additional uptake of the gas from the atmosphere.
Around half of the total CO2 absorption comes as a result of fresh “unsaturated” sea water entering the ocean as the ice melts. “The indirect effect of dilution on the seawater carbonate system through the promotion of CO2 uptake is an important factor driving acidification.”
The study concludes that acidification will be greatly amplified during summer months, when large swaths of the Arctic Ocean are no longer covered by sea ice, and during times of greatest sea ice decline.
The trend of “ice melt–driven CO2acidification” is likely to continue and become more pronounced over the next few decades until summer sea ice has disappeared completely.
As to what the impact of rapid acidification on marine life in the Arctic Ocean will be, the study’s authors call on their colleagues in related fields to begin investigating the issue.
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