Climate modelers from the University of New Hampshire have shown that the most likely explanation for the initiation of Antarctic glaciation during a major climate shift 34 million years ago was decreased carbon dioxide (CO2) levels. The finding counters a 40-year-old theory suggesting massive rearrangements of Earth's continents caused global cooling and the abrupt formation of the Antarctic ice sheet. It will provide scientists insight into the climate change implications of current rising global CO2 levels.
In a paper published today in Nature, Matthew Huber of the UNH Institute for the Study of Earth, Oceans, and Space and department of Earth sciences provides evidence that the long-held, prevailing theory known as "Southern Ocean gateway opening" is not the best explanation for the climate shift that occurred during the Eocene-Oligocene transition when Earth's polar regions were ice-free.
"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," says Huber. "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."
Oh, that nefarious Azolla. Wiped out an entire continent's worth of terrestrial ecosystem.