The impacts of climate change are being felt at even the deepest depths of the Antarctic ocean, a new study has found, in a discovery that may explain a 40 year old mystery.
In the mid-1970s, the first satellite images to be studied of Antarctica during the polar winter discovered a strange phenomenon. In the Weddell Sea, researchers noticed a huge ice-free region – known as a polynia – that remained open for three winters.
Scientists found that the polynia was kept open by warm waters that prevented ice from forming, but strangely, the event hasn’t reoccurred since and scientists assumed what they had witnessed was a rare event.
Now, a new study has suggested that such polynias used to be a commonly occurring phenomenon in the Antarctic, but have since been suppressed by the effects of climate change.
Researcher’s studied measurements gathered from the Antarctic ocean over a 60-year period, and found that the surface has been getting less salty since the 1950s as a result of melting glaciers and increased levels of precipitation.
This layer of fresher, less dense water on the surface prevents cold water currents from forming underneath. The scientists say that this has meant the warm waters from the deep ocean have been unable to rise and cause new polynias.
“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,” says Casimir de Lavergne, lead author of the paper.
The researchers also hypothesize that their findings could explain the slower rates of warming detected in the Antarctic region.
“If the warm waters aren’t able to release their heat to the atmosphere, then the heat is waiting in the deep ocean instead,” de Lavergne told LiveScience.
“This could have slowed the rate of warming in the Southern Hemisphere.”
The team adds that it is possible, though unlikely, that the Weddell Sea polynia will return, warning that if it does, it will release a pulse of decades-worth of heat and carbon from the deep ocean.