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article imageResearchers find new source of melting ice in Antarctic

By Karen Graham     Apr 19, 2018 in Science
A new study has revealed a previously undocumented process where melting glacial ice sheets change the ocean in a way that further accelerates the rate of ice melt and sea level rise.
Melting glaciers are just one of the symptoms of climate change, however, new research suggests they may also be a contributing factor. Scientists have discovered a previously unknown and rather vicious cycle that appears to be self-sustaining.
The researchers found that glacial meltwater makes the ocean's surface layer less salty and therefore, more buoyant, preventing any deep mixing in winter and allowing warm water in the depths to retain its heat and further melt glaciers from below.
The new research, led by Ph.D. student Alessandro Silvano with the Institute for Marine and Antarctic Studies (IMAS) at Australia's University of Tasmania, was published in the journal Science Advances on April 18, 2018.
“This process is similar to what happens when you put oil and water in a container, with the oil floating on top because it’s lighter and less dense,” said Silvano, reports Science Daily. He explains this the same thing that happens in Antarctica with fresh glacial meltwater, which stays above the warmer and saltier ocean water.
The great ocean conveyor belt
The great ocean conveyor belt
Intergovernmental Panel on Climate Change
The layer of cooler meltwater acts as an insulation blanket, shielding it from the cold Antarctic atmosphere, allowing it to further melt the glaciers from below. "We found that in this way increased glacial meltwater can cause a positive feedback, driving further melt of ice shelves and hence an increase in sea level rise," said Silvano.
Slowing of ocean current also found
Another negative aspect of this study was the finding that the meltwater is hampering the formation of denser water in certain parts of the Antarctic. These bodies of water would normally sink and help to drive ocean circulation, contributing to the absorption of heat and carbon dioxide.
However, Silvano says, "The cold glacial meltwaters flowing from the Antarctic cause a slowing of the currents which enable the ocean to draw down carbon dioxide and heat from the atmosphere. In combination, the two processes we identified feed off each other to further accelerate climate change."
Mr. Silvano points out that a similar scenario has been suggested as the reason for the rapid sea level rise of up to five meters per century at the end of the last Ice Age, around 15,000 years ago.
The edge of the Nansen Ice Shelf in Antarctica.
The edge of the Nansen Ice Shelf in Antarctica.
NASA/Christine Dow
"Our study shows that this feedback process is not only possible but is in fact already underway, and may drive further acceleration of the rate of sea level rise in the future, Silvano said.
Similar scenario in a previous study
More recently, as reported in Digital Journal, Researchers, led by University College London (UCL) and the Woods Hole Oceanographic Institution (WHOI) provided compelling evidence that the Atlantic Ocean's circulation - called Atlantic meridional overturning circulation (AMOC) - has been slowing down.
The UCL-WHOI study showed the influx of fresh water diluted the seawater, making it too light to sink to the depths of the ocean, disrupting the circulation. The research team reached this conclusion after examining sediment cores, measuring the size of sediment grains deposited by the deep-sea currents.
More about antarctic continental shelf, heat loss, brine release, Ice sheet, Sea level rise