Climate change affects oceans’ ability to sequester carbon dioxide

Research sponsored by the US Department of Energy has found that climate change has a big impact on the oceans’ ability to store excess carbon dioxide, with some oceans better able to sequester than others.

Scientists from the University of Illinois, Urbana-Champaign, admit that carbon sequestration in the deep ocean is at best a “technique to buy time”. However, they have found that the Atlantic Ocean’s ability to sequester carbon dioxide is particularly affected by climate change. Climate change would affect the ocean circulation, and therefore affect the retention time of carbon dioxide injected into the deep ocean, explains Atul Jain, a professor of atmospheric sciences at the University.

“Where you inject the carbon dioxide turns out to be a very important issue,” Jain added. He has developed an atmosphere-ocean, climate-carbon cycle model, which he has used to study the effectiveness of sequestration by the direct injection of carbon dioxide at a number of locations and depths.

When the model was run without climate feedback mechanisms affecting the oceans, the Pacific Ocean held the most carbon dioxide for the longest time. However, the addition of feedback mechanisms meant that the Atlantic Ocean was far superior. “Based on our initial results, injecting carbon dioxide into the Atlantic Ocean would be more effective than injecting it at the same depth in either the Pacific Ocean or the Indian Ocean,” said Jain.

According to the research, climate change affects both the uptake of the gas, and circulation patterns. As sea surface temperatures increase, the density of the water decreases, slowing down the ocean thermohaline circulation and decreasing the absorption of carbon dioxide. But at the same time, the reduced ocean circulation will decrease the ocean mixing, which decreases the ventilation to the atmosphere of carbon injected into the deep ocean.

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