Key melting Greenland glacier is growing again
But scientists believe that the growth of the Jakobshavn glacier will be short term
A major Greenland glacier that was one of the fastest-shrinking ice and snow masses on Earth is growing again, a new Nasa study has found.
In 2012, the Jakobshavn glacier was retreating about 3 kilometres and thinning nearly 40 metres a year.
But it started growing again about the same rate in the past two years, according to a study in Monday’s Nature Geoscience. Study authors and other scientists think this is temporary.
“That was kind of a surprise. We kind of got used to a runaway system,” said Professor Jason Box, an ice and climate scientist with the Geological Survey of Denmark and Greenland.
“The good news is that it’s a reminder that it’s not necessarily going that fast. But it is going.”
Prof Box, who was not part of the study, said Jakobshavn was “arguably the most important Greenland glacier because it discharges the most ice in the Northern Hemisphere. For all of Greenland, it is king.”
A natural cyclical cooling of North Atlantic waters probably caused the glacier to reverse course, said lead author Ala Khazendar, a Nasa glaciologist on the Oceans Melting Greenland project.
Dr Khazendar and colleagues say this coincides with a flip of the North Atlantic oscillation, which is a natural and temporary cooling and warming of parts of the ocean, like a distant cousin to El Nino in the Pacific.
The water in Disko Bay, where Jakobshavn hits the ocean, is about 2°C cooler than a few years ago, the study said.
This is good news on a temporary basis, but bad in the long term because it tells scientists that ocean temperature is a bigger player in glacier retreats than previously thought, said Nasa climate scientist Josh Willis, a study co-author.
Over the decades, the water has been and will be warming from man-made climate change, Mr Willis said.
He said about 90 per cent of the heat trapped by greenhouse gases goes into the oceans.
“In the long run, we’ll probably have to raise our predictions of sea level rise again,” Mr Willis said.
Think of the ocean temperatures near Greenland as an escalator rising slowly from global warming, Dr Khazendar said. The natural North Atlantic oscillation is sometimes like jumping down or jumping up a few steps.
The water can get cooler and have effects, but in the long run it is getting warmer and the melting will be worse, he said.
Four outside scientists said the study and results made sense.
University of Washington ice scientist Ian Joughin, who was not part of the study but predicted such a change seven years ago, said it would be a “grave mistake” to interpret the latest data as contradicting climate change science.
What’s happening, Mr 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".
Updated: March 26, 2019 09:26 AM