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article imageColder water is now slowing Greenland's fastest-melting glacier

By Karen Graham     Mar 26, 2019 in Environment
The fastest-shrinking glacier in Greenland has made an unexpected turn. Although it's been melting for 20 years, the Jakobshavn Glacier in West Greenland - famous for producing the iceberg that sank the Titanic - has now started growing again.
The Jakobshavn Glacier in West Greenland, the very same glacier that produced the iceberg that sank the Titanic, is growing again. While this may appear to be good news, scientists say this may be only temporary.
In a study published Monday in the journal Nature Geoscience, Ala Khazendar of NASA's Jet Propulsion Laboratory in Pasadena, California, and colleagues report the change in Jakobshavn's behavior and trace the source of the cooler water to the North Atlantic Ocean more than 600 miles (966 kilometers) south of the glacier.
The research is based on NASA's ongoing Oceans Melting Greenland (OMG) mission launched in 2015 with the express purpose of studying exactly how fast warm ocean waters are melting Greenland's glaciers from below.
An aerial view from NASA of the retreating Jakobsvahn glacier.
An aerial view from NASA of the retreating Jakobsvahn glacier.
The glacier had been retreating about 1.8 miles (3 kilometers) and thinning nearly 130 feet (almost 40 meters) annually since 2012. But about two years ago, it began growing again at the same rate, reports CTV News Canada.
According to the study, the OMG mission has recorded cold water near Jakobshavn for three years in a row. Khazendar said: "At first we didn't believe it. We had pretty much assumed that Jakobshavn would just keep going on as it had over the last 20 years."
The North Atlantic Oscillation (NAO) is probably the reason cold water was set in motion. This is because the weather circulation pattern from the NAO causes the northern Atlantic Ocean to switch slowly between warm and cold every five to 20 years.
This image taken by NASA s Operation IceBridge in Greenland shows the broad seemingly endless expans...
This image taken by NASA's Operation IceBridge in Greenland shows the broad seemingly endless expanse of the ice sheet.
NASA/Operation Ice Bridge
This particular climate pattern switched recently, driving colder waters along Greenland's southwest coast, which flowed up the west coast, eventually reaching Jakobshavn. Josh Willis of JPL, the principal investigator of OMG, explained, "Jakobshavn is getting a temporary break from this climate pattern. But in the long run, the oceans are warming. And seeing the oceans have such a huge impact on the glaciers is bad news for Greenland's ice sheet."
The water in Disko Bay, where Jakobshavn hits the ocean, is about 3.6 degrees cooler (2 degrees Celsius) than a few years ago, study authors said.
Arctic sea ice off Greenland.
Arctic sea ice off Greenland.
Good and bad news
This may seem to be good news, right now. But it is temporary. The bad news is that the retreat of the glacier will continue once the NAO cycle changes again. But more importantly, it gives scientists better insight into how ocean temperature plays a bigger part in glacier retreats and advances.
NASA climate scientist Josh Willis, a study co-author, says “In the long run we'll probably have to raise our predictions of sea level rise again."
University of Washington ice scientist Ian Joughin, who wasn't part of the study and predicted such a change seven years ago, said it would be a “grave mistake” to misinterpret the study as contradicting global warming.
What's happening, Joughin said, is “to a large extent, a temporary blip. Downturns do occur in the stock market, but overall the long term trajectory is up. This is really the same thing.”
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