Climate Change Reducing Ocean's Ability to Absorb Carbon Dioxide

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An oil and gas platform on fire in the ocean.

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Warmer temperatures is impacting how the ocean is able to absorb CO2 from the atmosphere. While the ocean acts as a natural carbon sink, global climate change is slowing its ability to suck up CO2 in large swaths of the subtropical North Atlantic, University of Wisconsin-Madison assistant professor Galen McKinley has shown in a new study. The ocean struggling to absorb CO2, and even slowing its absorption is something researchers realized a few years ago, but the reasons may be even more clear after this recent study.

University of Wisconsin Study

Looking outside of a plane at the ocean.

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University of Wisconsin-Madison reports, "Working with nearly three decades of data, the researchers were able to cut through the variability [that has caused conflicting results in previous studies] and identify underlying trends in the surface CO2 throughout the North Atlantic. During the past three decades, increases in atmospheric carbon dioxide have largely been matched by corresponding increases in dissolved carbon dioxide in the seawater...But the researchers found that rising temperatures are slowing the carbon absorption across a large portion of the subtropical North Atlantic. Warmer water cannot hold as much carbon dioxide, so the ocean's carbon capacity is decreasing as it warms."

Changing Ocean Chemistry

Buildings in Honolulu right beside the ocean with a plane wing in the foreground.

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Because the ocean has been absorbing more and more of the CO2 humans release into the atmosphere -- about a third of the planet's CO2 is taken in by the ocean -- the ocean has been becoming more acidic. Primary concerns of researchers have been both how to get the ocean to absorb ever more CO2 to help reduce what is in the atmosphere, and deal with the changing chemistry of the ocean which is impacting much of the flora and fauna. However, the results of this study show that as the ocean warms along with the planet, at least some parts of it will be less and less able to absorb CO2 from the atmosphere.

"More likely [than seeing the ocean's carbon levels surpass that of the atmosphere] what we're going to see is that the ocean will keep its equilibration but it doesn't have to take up as much carbon to do it because it's getting warmer at the same time," she says. "We are already seeing this in the North Atlantic subtropical gyre, and this is some of the first evidence for climate damping the ocean's ability to take up carbon from the atmosphere."

McKinley found these results after looking at data from 1981 to 2009 taken from broad samplings. She stresses that the same level of analysis needs to be extended to other areas beyond the North Atlantic to discover how other parts of the ocean are responding to carbon emissions and warming. This kind of information can be critical to the accuracy of carbon and climate modeling for future scenarios of global warming.