May 16, 2013 _ The Laurentide ice sheet once entombed Canada in two kilometres of ice, but all that is left is a blob of ice on Baffin Island now shrinking at a remarkable rate.
A new study says glaciers around the world are contributing almost as much to the rise of the world’s oceans as the Greenland and Antarctica ice sheets combined.
“And the largest contributor of all the regions is the Canadian Arctic,” says US glaciologist Alex Gardner, at Clark University, lead author the international study to be published Friday in the journal Science.
It says the glaciers are collectively losing almost as much ice each year as the Greenland and Antarctic Ice Sheets. Between 2003 and 2009, the researchers say the smaller glaciers poured approximately 260 billion tonnes of meltwater a year into the world’s oceans.
The largest contributions came from glaciers in Arctic Canada, followed by Alaska, coastal Greenland, the southern Andes and high-mountain Asia, says the study that tracked the contribution from 19 glaciated regions around the world.
There has been debate – and controversy – for years over how much glaciers are contributing to sea level rise. Particularly problematic were the estimates based on field measurements gathered by scientists who plant poles in glaciers and return yearly to gauge how much the ice has changed. Satellites, which have been able to “see” and measure the thickness of the world’s glaciers since 2003, indicated the glaciologists on the ground were overstating the shrinkage.
To sort out what is going on Gardner and leading ice scientists in Canada, the US and Europe pulled and reviewed the data for the 2003-2009 period to ensure they were comparing “apples with apples.”
It turns out that over the years scientists have tended to focus on smaller glaciers that are shrinking faster than glaciers in more inhospitable parts of the planet.
“The choice of sites was based more on convenience and cost than it was on scientific rationale,” says study co-author Martin Sharp, at the University of Alberta, who knows first-hand the difficulties of working in remote areas. His team studies glaciers on Devon Island in the high Arctic and it is major logical and financial challenge to keep the research going, says Sharp, who spent more than $30,000 to get two researchers onto Devon this spring.
The researchers say the problems associated with focusing on smaller, more convenient glaciers were compounded when researchers extrapolating their findings to entire regions assuming all glaciers behaved in the same way.
And while the satellites do get the big picture, the new study found they have not been picking up subtle but important changes in the ice. Sharp stresses the importance of collecting data on the ground to ensure satellite data is properly interpreted.
The study provides what the scientists are calling a ”consensus” that gives a more refined picture of how the glaciers contribute to sea level rise.
It shows that central Europe is losing ice at the fastest rate – so fast that many small glaciers in the Alps could disappear by the end of this century.
But Canada’s Arctic is pouring the most water into the oceans, the study says. This is because the region is warming – summer temperatures have repeatedly shattered records in the last decade – and because Canada’s Arctic contains so many glaciers.
Gardner says the ice in Canada’s Arctic contains 3.5 times more water than the Great Lakes. “That’s how much water we are talking about,” he says, pointing to the Barnes Ice Cap on Baffin Island for perspective.
“It’s the former Laurentide ice sheet, which used to cover most of North America, and still lives today on Baffin Island,” he said.
Gardner’s work has shown the Barnes, which is now about 150 km long and half a kilometre at its thickest point, is losing close to a metre in height a year, twice the rate it was skrinking 50 years ago.
“Essentially it is a blob that is melting away now,” says Gardner. “It’s just an ice cube, but an ice cube that contains vastly more ice than all of Europe just in that one little dot in the Canadian Arctic.”
While the melt is accelerating, Gardner says the Barnes, like most of Canada’s Arctic glaciers, is not going to disappear anytime soon. He says the glaciers are so big they will be around contributing to sea level rise for hundreds of years.
Scientists say that global sea level is now rising at just over two millimeters a year. “That sounds small but that has significant impacts on low-lying communities,” Gardner says.
Researchers forecast the oceans could rise by up to a metre by the end of the century, which would drown low lying around the world that are home to millions of people.