Oceans hid CO2 during last ice age

Processes in the ocean are responsible for rises in carbon dioxide (CO2) since the most recent ice age, says a study led by scientists at Bern University.

An international team of glaciologists found that the close connection between CO2 and temperature has existed over the past 800,000 years: with low CO2 concentrations during the ice ages and higher CO2 values during warm periods.

They then tried to work out where the carbon dioxide was hidden during the ice ages and how it got back into the atmosphere when they ended.

“We’ve been able to identify processes in the ocean which are connected to the observed rise in CO2,” said Jochen Schmitt, researcher at the Oeschger Centre for Climate Change Research at Bern University and lead author of the study, published in the scientific journal Science.

According to Schmitt, during the ice age more and more carbon dioxide accumulated in the deep ocean, causing the concentration of atmospheric CO2 to drop. Only at the end of the ice age was this stored CO2 transported back to the sea surface through changing ocean circulation and thus emitted back into the atmosphere.

“In addition to the scientific curiosity about how our Earth functioned in the past, the main question to be asked is how the Earth will develop under the influence of man,” Schmitt said.

These are important scenarios for the future because the CO2 content in the atmosphere has never been anywhere near as high over the past 800,000 years as today, he added.