Climate Change: Extinction of Ice-Free Antarctic Polynyas Due to Trapped Ocean Heat

Scientists have discovered that heat from the depths of the ocean is being trapped under the Antarctic ice shelf because of climate change.

Researchers from the McGill University and University of Pennsylvania have found evidence to show climate change is the main reason for the disappearance of ice-free regions, known as polynyas.

In the 1970s, scientists studied a large, open body of water within the Southern Ocean's Weddell Sea. The phenomenon of polynya was thought to be rare, but recent research has discovered they may disappear entirely because climate change is trapping heated water beneath the ocean, which stops the ice-free regions forming.

Eric Galbraith told CTVNews.ca: "The fact that we can still have a surprise like this after studying the climate system for decades shows just how complex and dangerous [climate change] is."

Researchers analysed data from robot ships that have sailed around the area for the last 60 years. Increased precipitation in the Southern Ocean and the melting of glaciers in Antarctica has filled the ocean with large amounts of freshwater, preventing the warm water underneath from rising to the top.

Beneath the freshwater, deep ocean heat has been unable to escape and melt the Antarctic ice pack that forms in the winter.

Gailbraith added the deep ocean is like the "basement of the climate system". Without polynya, there is a "trapped door" to this system.

He added: "Just like fish in a fish tank that rely on an aerator, deep-sea fish need oxygen to be supplied from the air above. It will take many decades for the oxygen to get used up, but eventually it will make it hard for the deep sea fish to breathe."

The study was published in the journal Nature Climate Change.

As reported by Headlines and Global News, Casimir de Lavergne, the lead author of the study, said: "Deep ocean waters only mix directly to the surface in a few small regions of the global ocean. So this has effectively shut one of the main conduits for deep ocean heat to escape."

The research also revealed evidence of a predicted increase in the amount of precipitation over the Southern Ocean, as well as a rise in levels of atmospheric carbon dioxide.

Professor Jaime Palter, co-author of the study, said in a statement: "This agrees with the observations, and fits with a well-accepted principle that a warming planet will see dryer regions become dryer and wetter regions become wetter."

She added: "True to form, the polar Southern Ocean - as a wet place - has indeed become wetter. And in response to the surface ocean freshening, the polynyas simulated by the models also disappeared."