April 5, 2012
Rising Carbon Dioxide Levels Aided End Of Ice Age
A new study published in the journal Nature provides evidence that rising carbon dioxide levels brought an end to the last Ice Age.
The researchers analyzed prehistoric global warming and found that permafrost released massive amounts of carbon dioxide that was stored in frozen soil in Polar Regions.
This resulted in climate change and increased global temperatures and ocean acidifications, ending the Ice Age.
Lead author Jeremy Shakun said the key to understanding the role of carbon dioxide it to reconstruct globally averaged temperature changes during the end of the last Ice Age.
"Carbon dioxide has been suspected as an important factor in ending the last Ice Age, but its exact role has always been unclear because rising temperatures reflected in Antarctic ice cores came before rising levels of CO2," Shakun, who is a National Oceanic and Atmospheric Administration (NOAA) Post-doctoral Fellow at Harvard University and Columbia University, said in a press release.
The team believes that small changes in the Earth's orbit around the sun affected the amount of sunlight striking the northern hemisphere, which caused the ice to melt in Canada and Europe.
This ice turned into fresh water, which flowed off of the continent and into the Atlantic Ocean, where it formed a lid cover the sinking end of the Atlantic Meridional Overturning Circulation. This area is part of a global network of currents that brings warm water up from the tropics and keeps Europe temperate despite its high latitudes.
The researchers said when the fresh water draining off the continent at the end of the Ice Age entered the North Atlantic, it essentially put the brakes on the current and disrupted the delivery of heat to the northern latitudes.
"When the heat transport stops, it cools the north and heat builds up in the Southern Hemisphere," Shakun said in the press release. "The Antarctic would have warmed rapidly, much faster than the time it takes to get CO2 out of the deep sea, where it was likely stored.
"The warming of the Southern Ocean may have shifted the winds as well as melted sea ice, and eventually drawn the CO2 out of the deep water, and released it into the atmosphere," Shakun said. "That, in turn, would have amplified warming on a global scale."
The team found that the average temperature around the Earth at the end of the Ice Age correlated with rising levels of carbon dioxide.
Peter Clark, an Oregon State University scientist and co-author on the paper, said the changes in solar radiation was the likely culprit behind the effects that followed.
The researchers said they now want to determine how human-generated carbon dioxide will affect the planet when there is not an ice age.
"CO2 was a big part of bringing the world out of the last Ice Age," Shakun said, "and it took about 10,000 years to do it. Now CO2 levels are rising again, but this time an equivalent increase in CO2 has occurred in only about 200 years, and there are clear signs that the planet is already beginning to respond."
"While many of the details of future climate change remain to be figured out, our study bolsters the consensus view that rising CO2 will lead to more global warming," Shakun added.