The injection, or sequestration, of the greenhouse gas carbon dioxide into the ocean floor is commonly suggested as a possible way to slow the effects of climate change by preventing its escape into the atmosphere, but the UI research has shown the atmosphere interacts with the oceans, making sequestration capacity and net uptake of carbon dioxide subject to the effects of climate change.

"Through a number of physical and chemical interactive mechanisms, the ocean circulation could change and affect the retention time of carbon dioxide injected into the deep ocean, thereby indirectly altering oceanic carbon storage and atmospheric carbon dioxide concentration," said team leader Atul Jain.

"Where the carbon dioxide is injected turns out to be a very important issue."

The team's Integrated Science Assessment Model is described in the September issue of the Journal of Geophysical Research (Oceans) as a composite climate-ocean-terrestrial biosphere-carbon cycle modelling system that explores physical and chemical interactions among individual components, including carbon cycle, climate change and ocean circulation.

"A good understanding of climate change, ocean circulation, the ocean carbon cycle and feedback mechanisms is crucial for a reliable projection of atmospheric carbon dioxide concentration and resultant climate change," Jain said.

Using its model, the team were able to study the effectiveness of oceanic carbon sequestration by assessing the results of direct carbon dioxide injection at different locations and depths, finding that climate change would dramatically affect the oceans' ability to store carbon dioxide, particularly in the Atlantic Ocean.

"When we ran the model without the climate feedback mechanisms, the Pacific Ocean held more carbon dioxide for a longer time," team member Long Cao said.

"When we added the feedback mechanisms, however, the retention time in the Atlantic Ocean proved far superior. 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."

Although initial findings showed positive results for the Atlantic, increasing surface temperatures due to climate change would decrease water density, slowing ocean thermohaline circulation and decreasing the absorption of carbon dioxide.

"The reduced ocean circulation will decrease the ocean mixing, which decreases the ventilation to the atmosphere of carbon injected into the deep ocean," said Jain.

"Our model results show that this effect is more dramatic in the Atlantic Ocean."

According to the data collected by the team, sequestering carbon in the ocean is only likely to provide a temporary solution to climate change.

"Carbon dioxide dumped in the oceans won't stay there forever," Jain said.

"Eventually it will percolate to the surface and into the atmosphere."

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