Apr 24, 2018
Bolstering concerns that so-called "feedback loops" should be considered a legitimate and serious concern, a new study shows that a worrying hypothesis put out just three years ago about the impacts of melting Antarctic ice may already have started coming true.
In a paper published in Science Advances, researchers at the University of Tasmania and other institutions found that the melting of Antarctica's glaciers has begun to trigger a "feedback loop" in which that melting's effects on the oceans cause even more ice sheets to deteriorate, and so on.
Chris Mooney of the Washington Post described the feedback loop phenomenon as "one of the most worrisome predictions about climate change" in an article about the findings.
"What we found is not only a modeling study but is something that we observed in the real ocean," Alessandro Silvano, one of the researchers, told the Post. "Our study shows for the first time actual evidence of this mechanism. Our study shows that it is already happening."
As Common Dreams reported in 2015, NASA climate scientist James Hansen first raised concerns about the feedback loop then. As the Post reports, Hansen explained that the melting of glaciers would create fresh water, blocking cold salt water from sinking to the bottom of the ocean and protecting the ice shelves from melting:
When cold surface water no longer sinks into the depths, a deeper layer of warm ocean water can travel across the continental shelf and reach the bases of glaciers, retaining its heat as the cold waters remain above. This warmer water then rapidly melts the glaciers and the large floating ice shelves connected to them.
The continuous melting cycle could soon begin to cause rapidly-rising sea levels and destructive hurricanes and other storms.
"That would mean loss of all coastal cities, most of the world's large cities and all their history," said Hansen when his paper on the feedback loop theory was released.
Hansen told the Post that the new research "provides a nice small-scale example" of the patterns he predicted.
"If we stay on business-as-usual [greenhouse gas] emissions rates, so that global warming continues to increase, I expect that the freshwater injection rate will increase (mainly via ice faster ice shelf breakup and underwater melt) and sea ice area will increase. This experiment will be playing out over the next years and decades," said Hansen in an email to the Post.
Anders Levermann, a climate scientist at the Potsdam Institute for Climate Impact Research, noted that it was "curious" that the feedback loop "is occurring now, after 10,000 years of stability, while we are ramping up the temperature of the planet."
"Trying to dismiss the idea that it has anything to do with global warming is also very difficult," he told the Scientific American.
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