Although conditions at the end of the last ice age were very different to today, this study highlights the importance that dynamic features such as sea ice have on regulating the climate system.
- Jenny Roberts
A new study reconstructing conditions at the end of the last ice age suggests that as the Antarctic sea ice melted, massive amounts of carbon dioxide that had been trapped in the ocean were released into the atmosphere.
The study includes the first detailed reconstruction of the Southern Ocean density of the period and identified how it changed as the Earth warmed. It suggests a massive reorganisation of ocean temperature and salinity, but finds that this was not the driver of increased concentration of carbon dioxide in the atmosphere. The study, led by researchers from the University of Cambridge, is published in the journal Proceedings of the National Academy of Sciences.
The ocean is made up of different layers of varying densities and chemical compositions. During the last ice age, it was thought that the deepest part of the ocean was made up of very salty, dense water, which was capable of trapping a lot of CO2. Scientists believed that a decrease in the density of this deep water resulted in the release of CO2 from the deep ocean to the atmosphere.
However, the new findings suggest that although a decrease in the density of the deep ocean did occur, it happened much later than the rise in atmospheric CO2, suggesting that other mechanisms must be responsible for the release of CO2 from the oceans at the end of the last ice age.
“We set out to test the idea that a decrease in ocean density resulted in a rise in CO2 by reconstructing how it changed across time periods when the Earth was warming,” said the paper’s lead author Jenny Roberts, a PhD student in Cambridge’s Department of Earth Sciences who is also a member of the British Antarctic Survey. “However what we found was not what we were expecting to see.”
Read the full story
Image: Foraminifera
Credit: Jenny Roberts
Reproduced courtesy of the University of Cambridge
____________________________________________