Princeton Study - Southern Ocean Current May Hold Key To CO2 Levels

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Circulation in the waters near the Antarctic coast may be one of the planet's critical means of regulating levels of carbon dioxide in the Earth's atmosphere, according to Princeton researchers.

Though climate scientists have long debated the reasons behind the variation in atmospheric levels of carbon dioxide that occur over lengthy periods in Earth's history, the Princeton team may have found a clue to where the answer can be found. In a new research paper, the team reveals that the waters in the Southern Ocean below 60 degrees south latitude, the region that hugs the continent of Antarctica, play a far more significant role than was previously thought in regulating atmospheric carbon, and -- in contrast to past theories -- the waters north of this region do comparably little to regulate it.

"Cold water that wells up regularly from the depths of the Southern Ocean spreads out on the ocean's surface along both sides of this dividing line, and we have found that the water performs two very different functions depending on which side of the line it flows toward," said Irina Marinov, the study's lead author. "While the water north of the line generally spreads nutrients throughout the world's oceans, the second, southward-flowing stream soaks up carbon dioxide, a greenhouse gas, from the air. Such a sharply-defined difference in function has surprised us. It could mean that a change to one side of the cycle might not affect the other as much as we once suspected." The research team, which also includes Princeton's Jorge Sarmiento as well as the National Oceanic and Atmospheric Administration's Anand Gnanadesikan and Robbie Toggweiler, will publish their results in today's (June 22) issue of the scientific journal, Nature. Marinov, who led the study while working in Sarmiento's lab, is currently pursuing postdoctoral research at the Massachusetts Institute of Technology as a NOAA Fellow in Climate and Global Change.

The Southern Ocean has long been of interest to scientists, who have found that it influences the rest of the planet in many ways. Two years ago, Sarmiento's research team discovered that the nutrients in the world's oceans were dependent on the Southern Ocean's circulation pattern, but had not realized how the pattern affected the atmospheric carbon cycle.

Scientists have also been aware that cold Antarctic waters have the ability to absorb atmospheric carbon dioxide, which could make the region one of the planet's lines of defense against rising greenhouse gas levels. These and other effects the Southern Ocean has on the Earth are not themselves new to science, but distinctions between one effect and another have been difficult to draw. "The new paper shows that carbon dioxide and nutrient flow are separated quite dramatically," said Sarmiento, a professor of geosciences. "What we are trying to do is understand better the balance of forces that help our planet maintain a steady environmental state, so we can anticipate what might cause that state to change. This paper helps us clarify how those forces interact."

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