A Massive Ice 'Lid' in the Antarctic Melted and Released a Massive Amount of CO2

At the end of the last ice age, something strange and fantastic may have happened. Scientists have found that during this period, the melting of a massive ice "lid" in the Antarctic released a massive amount of carbon dioxide that had been trapped in the ocean.

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.

New findings, though, 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.

In this latest study, the researchers studied the chemical composition of microscopic shelled animals that had been buried in ocean sediment since the end of the last ice age. This revealed that during the cold glacial periods, the deepest water was significantly denser than it is today. However, what was unexpected was the timing of the reduction in the deep ocean density, which happened about 5,000 years after the initial increase in CO2, which means that the density decrease couldn't be responsible for releasing CO2 to the atmosphere.

So what happened? The researchers believe that like a bottle of wine with a cork, sea ice prevented CO2 rich water from releasing its CO2 to the atmosphere. The expansion of sea ice during the last ice age acted as a "lid" on the Southern Ocean. When that ice melted, CO2 escaped.

"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, and emphasizes the need for improved understanding and prediction as we head into our ever warming world," said Jenny Roberts, one of the researchers, in a news release.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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