Thirty-four million years ago the Antarctic glaciated, forming an ice sheet rather abruptly. For the past 40 years, the textbook theory for this formation was that shifting continents induced a worldwide cooling phenomenon and the ice sheet took shape.
Researchers at the University of New Hampshire are proponents of a different theory of Antarctic ice sheet formation--the CO2 reduction theory. While many have supported the idea that declining atmospheric levels of CO2 during the Eocone-Oligocene transition caused the ice sheet to form, there hasn't been enough evidence to back the theory and convince naysayers, until now.
To "flip the whole story on its head", UNH climate scientists led by Matthew Huber modeled the formation of the ice sheet under varying levels of CO2. They set up the environment in which ice sheet formed from low CO2 levels and found that the formation itself would have influenced ocean currents and climate patterns, furthering the glaciation.
Previous research supporting the opposing, continental theory argued that the effects of continental rearrangement--mainly the opening of the Southern Ocean "gateway" when Australia shifted away from Antarctica--affected climate patterns to the point of ice sheet formation. Proponents of this theory explain that isolating the polar continent, leaving it bereft of warm tropical waters, changed the climate and circulation patterns so drastically that it induced a glacial period. Huber and colleagues, however, believe that previous research overlooked the actual formation of the ice sheet as a major player in further glaciation and ignored its effects on the climate system.
Huber does, however, acknowledge that continental rearrangment, by opening up the Southern Ocean gateway, may have contributed to the decline of CO2, but it most likely did not directly affect the climate the way the CO2 drawdown and initial formation of the ice sheet did. The reorganization of the continents may have created regions of nutrient-rich waters saturated with plankton that died and sank to the bottom of the ocean, taking with them massive amounts of carbon.
"It should be clear that resolving these two very different conceptual models for what caused this huge transformation of the Earth's surface is really important because today as a global society we are, as I refer to it, dialing up the big red knob of carbon dioxide but we're not moving continents around," said Huber.