With that in mind, a team from Colorado State University and Scripps Institution of Oceanography, both in the US, has modelled the uptake and circulation of carbon in the Southern Ocean at high resolution.
"The atmosphere overlying the Southern Ocean is undergoing significant climate change, namely the positive trend in the southern annular mode," Taka Ito of Colarado State told environmentalresearchweb. "Due to ozone depletion and global warming, this climate trend is likely to continue for the decades to come. We are concerned about its impact on the ocean currents, sea ice, ecosystem and the rate of carbon uptake."
The researchers combined an ocean-circulation model with a carbon-cycle model, focusing on the period from January 2005 to December 2006.
"For the first time, my research group and collaborators at Massachusetts Institute of Technology successfully simulated the carbon cycle of the Southern Ocean at a very high resolution using one of the world’s most powerful computers at NASA," said Ito. "The Southern Ocean is filled with chaotic eddies that are equivalent of weather system in the atmosphere. Simulating these features requires massive computational power."
The uptake of carbon peaked at the Antarctic polar front, the researchers discovered. The carbon was then transported away by the ocean circulation, with Ekman flow – water motion caused by the wind – acting as the main mechanism.
"We found that there is an intimate connection between climate variability and carbon uptake of the Southern Ocean," said Ito. "The model calculation demonstrated that changing atmospheric winds indeed control the transport of carbon dioxide within the ocean and so the rate of oceanic carbon uptake."
Westerly winds in the Southern Ocean region have become stronger in recent years. This could increase uptake of manmade carbon dioxide from the atmosphere and boost its transport to waters further north. But it’s not clear how the ocean’s eddy fluxes will respond. And stronger winds could also cause more upwelling of deep waters, resulting in the release of natural carbon dioxide to the atmosphere.
"It is not yet clear how this effect alters climate prediction for this century, as there are many other factors that influence atmospheric carbon dioxide," said Ito. "Our result implies that climate change can significantly influence the global carbon cycle. Changes in oceanic carbon sink, in turn, affect the atmospheric carbon dioxide and climate. This circular argument – carbon dioxide is the cause and consequence of climate change – indicates complex interplay which governs the long-term evolution of our planet."
The researchers reported their work in Nature.