Upside-down "rivers" of warm ocean water may be one of the causes of Antarctica's ice shelves breaking up, leading to a rise in sea levels. But a new study suggests an increase in sea ice may lead to a much more devastating change in the Earth's climate — another ice age.

Using computer simulations, the research suggests that an increase in sea ice could significantly alter the circulation of the ocean, ultimately leading to a reverse greenhouse effect as carbon dioxide levels in the ocean increase and levels in the air decrease.

"One key question in the field is still what caused the Earth to periodically cycle in and out of ice ages," University of Chicago professor and the study's co-author, Malte Jansen, said in a statement. "We are pretty confident that the carbon balance between the atmosphere and ocean must have changed, but we don't quite know how or why."

The last major ice age ended at the end of the Pleistocene era, about 2.5 million years ago, as glaciers have periodically grown and then gotten smaller. Researchers believe that changes to the Earth's orbit may be partly responsible for some of the Earth's cooling, but additional factors have likely played a part, Jensen added.