Nature & Environment
Antarctic Ice Sheet First Grew with Decreasing CO2 in the Ancient Past
Catherine Griffin
First Posted: Jul 31, 2014 08:43 AM EDT
Scientists have managed to overturn a 40-year-old theory about the Antarctic glaciation that occurred 34 million years ago. It turns out that this increase in ice was caused by decreased carbon dioxide levels, which could shed a bit more light on current climate shifts.
In the past, researchers believed in a theory called the "Southern Ocean gateway opening," which occurred during the Eocene-Oligocene transition. Yet it appears that this theory may not be as solid as once believed.
"The Eocene-Oligocene transition was a major event in the history of the planet and our results really flip the whole story on its head," said Matthew Huber, one of the researchers, in a news release. "The textbook version has been that gateway opening, in which Australia pulled away from Antarctica, isolated the polar continent from warm tropical currents, and changed temperature gradients and circulation patterns in the ocean around Antarctica, which in turn began to generate the ice sheet. We've shown that, instead, CO2-driven cooling initiated the ice sheet and that this altered ocean circulation."
So how did the researchers find out that CO2 drove this cooling? The scientists modeled the Eocene-Oligocene world as if it contained an Antarctic ice sheet of near-modern size and shape. Then, they explored the results within the same kind of coupled ocean-atmosphere model used to project future climate change and across a range of CO2 values that are likely to occur in the next 100 years.
"One of the things we were always missing with our CO2 studies, and it had been missing in everybody's work, is if conditions are such to make an ice sheet form, perhaps the ice sheet itself is affecting ocean currents and the climate system-that once you start getting an ice sheet to form, maybe it becomes a really active part of the climate system and not just a passive player," said Huber.
While it's apparent that a drawdown of CO2 caused this cooling, researchers are unsure what caused the drawdown in the first place. These findings, though, do have implications for future climate models as we release more and more of this gas into our atmosphere.
The findings are published in the journal Nature.
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First Posted: Jul 31, 2014 08:43 AM EDT
Scientists have managed to overturn a 40-year-old theory about the Antarctic glaciation that occurred 34 million years ago. It turns out that this increase in ice was caused by decreased carbon dioxide levels, which could shed a bit more light on current climate shifts.
In the past, researchers believed in a theory called the "Southern Ocean gateway opening," which occurred during the Eocene-Oligocene transition. Yet it appears that this theory may not be as solid as once believed.
"The Eocene-Oligocene transition was a major event in the history of the planet and our results really flip the whole story on its head," said Matthew Huber, one of the researchers, in a news release. "The textbook version has been that gateway opening, in which Australia pulled away from Antarctica, isolated the polar continent from warm tropical currents, and changed temperature gradients and circulation patterns in the ocean around Antarctica, which in turn began to generate the ice sheet. We've shown that, instead, CO2-driven cooling initiated the ice sheet and that this altered ocean circulation."
So how did the researchers find out that CO2 drove this cooling? The scientists modeled the Eocene-Oligocene world as if it contained an Antarctic ice sheet of near-modern size and shape. Then, they explored the results within the same kind of coupled ocean-atmosphere model used to project future climate change and across a range of CO2 values that are likely to occur in the next 100 years.
"One of the things we were always missing with our CO2 studies, and it had been missing in everybody's work, is if conditions are such to make an ice sheet form, perhaps the ice sheet itself is affecting ocean currents and the climate system-that once you start getting an ice sheet to form, maybe it becomes a really active part of the climate system and not just a passive player," said Huber.
While it's apparent that a drawdown of CO2 caused this cooling, researchers are unsure what caused the drawdown in the first place. These findings, though, do have implications for future climate models as we release more and more of this gas into our atmosphere.
The findings are published in the journal Nature.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone