Scientists Piece Together the Puzzle of Earth's Last Ice Age

It seems blatantly obvious that an extremely cold climate spurred Earth's last Ice Age - officially known as the "Last Glacial Maximum" (LGM) - but scientists have long suspected that other factors were at play, and are just now piecing together the rest of the puzzle.

"We have all these scattered pieces of information about changes in the ocean, atmosphere, and ice cover," Raffaele Ferrari, the Breene M. Kerr Professor of Physical Oceanography in MIT's Department of Earth, Atmospheric and Planetary Sciences, said in a statement, "and what we really want to see is how they all fit together."

Ice ages, like the one that occurred 21,000 years ago, are set in motion as the Earth slowly transits around the Sun. Researchers agree that this solar-energy decrease alone wasn't enough to cause this glacial state - they have since looked to the oceans for the answer.

Oceans are powerful regulators of the Earth's climate and can store vast amounts of carbon for thousands of years, preventing it from turning into harmful carbon dioxide (CO2) emissions.

Although the ocean's ability to trap carbon is a positive attribute considering the current concern for climate change, oceans do need to "breathe" carbon in and out.

In this study, researchers focused on the Southern Ocean that encircles Antarctica. It is a critical part of the carbon cycle because it provides a connection between the atmosphere and the deep ocean abyss. The Southern Ocean, helped along by whipping winds that mix waters, is one of the only places where the deepest carbon-rich waters ever rise to the surface, to "breathe" CO2 in and out.

But during the LGM, sea ice stretched great distances over the Southern Ocean, limiting its ability to exchange CO2 with the atmosphere. The Southern Ocean was literally being suffocated by the ice, and forced to harbor CO2 in its waters, causing the drastic drop in CO2 levels during the last Ice Age.

The findings were reported in the journal Proceedings of the National Academy of Sciences.