Greenland is losing so much ice that its gravity is getting weaker: researcher
Greenland is losing 30 million tonnes of ice every hour, a new study suggests
The Greenland ice cap is losing an average of 30 million tonnes of floating ice on average per hour — faster than scientists had previously estimated, according to a study published in the journal Nature.
William Colgan, who works as a senior researcher with the Geological Survey of Denmark and Greenland, said in a year, that's 40 per cent more than all of Canada's annual water use.
"The visuals are quite staggering, if you get up there," Colgan told The Current's Matt Galloway.
The loss of ice is so great that Greenland's gravity is getting weaker.
"Greenland is a relatively massive object, and it holds sort of a permanent tide of water close to it," Colgan explained.
"So as Greenland begins to get smaller, its gravity begins to get weaker, and that water that it holds tight begins to slosh away to faraway places in the world where the gravity is not weakening."
And as Colgan notes, the 30-million figure only takes into account the floating ice around the edges of the glacier. If you factor in the entire ice sheet, including below sea level, the total ice loss is around 9,000 and 10,000 tonnes a second, he estimated.
That amount of freshwater being dumped into the ocean is concerning for some scientists, including the study's lead researcher.
"The changes around Greenland are tremendous and they're happening everywhere. Almost every glacier has retreated over the past few decades," Chad Greene, at Nasa's Jet Propulsion Laboratory, told The Guardian.
Dumping freshwater into the North Atlantic Ocean weakens the Atlantic meridional overturning circulation, a system of ocean currents that circulates water within the Atlantic Ocean, bringing warm water north and cold water south.
Greene isn't sure exactly how much it's currenlly being weakened, however.
Noticeable changes
Colgan says most of the global effect of Greenland's mass ice loss is felt in the Southern Hemisphere.
"On the flip side, when Antarctica loses mass and weakens its gravity, that's when the sea level is felt in the Northern Hemisphere," he said.
There's still an impact on Canadian water levels, though — but that's felt differently between the coasts due to factors including fluctuating air and ocean currents, according to Colgan.
He said the sea level rise in Vancouver, for example, is also affected by a phenomenon called subsidence — the sinking of the ground when the earth beneath the surface shifts, either by natural processes or human activity.
"It's going in the wrong direction, versus in northern Canada, we have so much uplift that sea levels might be actually falling in relative terms; where the land is rising out of the ocean, the ocean is sort of falling off the shoreline."
Colgan says it's tough to tell what impact the meltwater from Greenland will have on species in the ocean's depths.
"There's definitely a handful of studies that suggest more meltwater means more nutrients and more upwelling of fjords" — when deep, cold water rises toward the surface — "which will generally be good for productivity or primary productivity of the ocean and help fisheries," he said.
"But then there's also some studies saying … if you get too much of this freshwater, you can start to have freshwater caps on the ocean, which reduce the vertical overturning."
Oceans are also getting more acidic as more carbon dioxide from the melted ice dissolves into them. Colgan says that's generally bad for fisheries' productivity.
"It's hard to tell because the fisheries are also highly managed human resource," he said. "So looking for the impact of a natural process on the fisheries is pretty challenging."
Colgan said he'll be back in Greenland in May to work on a big crevasse field — a massive crack in the ice sheet — in the central-western part of the region, and then again in August in northwest Greenland.
"The crevasses are phenomenally large. They're 20 metres wide and five kilometres long and quite bottomless," he said. "They weren't there 20 years ago."
"So we think they're telling us that the ice sheet is a little more sensitive dynamically to climate change than we expected. So watching this crevasse field evolve year after year is pretty profound indeed."
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Produced by Amanda Grant.
