October 5, 2007
Brain freeze: researchers puzzle over rapidly melting Arctic ice
Researcher says not enough is known to forecast the North’s future
by Michael Brown
While a recent report claiming the Arctic ice cap has shrunk to a record low has sent many among us scrambling for higher ground, one University of Alberta researcher says not enough is known about the process to be sure what exactly the future holds.
Last month the U.S. National Snow and Ice Data Center reported that Arctic sea ice, which melts back during the summer months only to return again in the winter, was reduced by more than a million square kilometres, or twice the size of Newfoundland. The summer melt exceeded the previous record set in 2005.
Although the summer brought an off-the-charts thaw, the University of Alberta’s newest import, Christian Haas, says sea ice shrinkage is a largely misunderstood process because its causes are misunderstood.
“It’s all related to global warming, but everybody is confused as to why it went so quick this year – this year wasn’t that warm,” said Haas, a professor in the Department of Earth and Atmospheric Sciences whose expertise is sea ice thickness. “There are large discrepancies in these sea ice models – they underestimate the shrinkage compared to what is really observed, and this is showing us that we still don’t understand it.”
Haas says sea ice plays an important role in the radiation balance of the Earth. When there is a lot of sea ice, the surface of the ocean is considered “white” and most of the solar radiation is reflected back into space. However, when the sea ice coverage shrinks, “dark” ocean surface is exposed to the sun, more heat is absorbed, increasing the ice melt that has led to a nine per cent decrease in the size of Arctic ice shelf per decade since records started being kept in the mid-1970s.
Haas says this is now a universally accepted theory concerning global warming, but warns about making generalizations because many of the forces that influence sea ice are misunderstood or simplified.
“For instance, ice thickness has been slightly increasing in the Antarctic,” he said. “This shows us there are two distinct climate systems. An ice mass dominates the South, while the Arctic Ocean, surrounded by land, is much more affected by warming and the currents.”
As well, Haas says simplifying global warming to a bottom line of melting discounts the role of the many individual systems, thousands of years in the making, that work together to make up the Arctic.
For instance, ocean and wind currents play a substantial part in the annual retreat of Arctic sea ice. Haas says together, they promote a lumbering sea ice drift that starts on the Siberian side of the Arctic, where the retreat is the most pronounced, and slides towards North America. These important winds are regulated by sea level pressure, which has “very much decreased over the last 20 years.”
Haas explained further that the Arctic’s delicate ecology is also at the mercy of the containment of the Gulf Stream, the current that pumps Caribbean-heated waters north, delivering relatively warm salt water (up to 2.2 C) into the Arctic. Were it not for a layer of freshwater run-off that drains into the Arctic Ocean during the summer melt – acting as both an insulator against these warm waters and an ice builder – sea ice in the North would certainly disappear.
“This interplay is dependent on where the fresh water goes from the rivers and how much fresh water comes in here,” said Haas, pointing out that what is happening inland may have a direct correlation to what is happening in the Arctic Ocean.
And that is just the tip of the iceberg. Haas said while many systems are understood, the information about some variables, such as sea ice thickness, is incomplete, rendering current climate models inaccurate.
Haas says ice thickness integrates all these processes of ice dynamics and ice motion, but it has been studied only sporadically throughout the years, leaving the body of information lacking.
Haas’s own studies began with his ice thickness observation program in the region of the North Pole back in 1991, when he was a researcher with the Alfred Wagener Polar Research Institute in Germany. With five readings in the following 13 years, Haas noted a 20 per cent decrease in ice thickness at the Pole, to just two metres in thickness. However, thickness is not a constant across the Arctic, says Haas, whose more recent tests have shown an increase in ice thickness in other areas of the Arctic, including ice measured off the coast of Ellesmere Island.
To help resolve this paradox, Haas has developed an airborne electromagnetic induction sounding technique which allows him to map large regions of ice thickness in a short time.
“I generate a low-frequency electromagnetic frequency to map the ice,” said Haas, who conducted the first of these tests in 2004 using a helicopter survey. “I would like to map it six more times at least, so I have 10 years of results and a relevant sample size.”
Haas, whose profile will be instrumental in bolstering the U of A’s Canadian Circumpolar Institute, made the move to the U of A in part because of promises of increased Arctic visits to better fill in the gaps left in his sea ice thickness studies. Whether or not there is something to measure in the coming years, Haas is hopeful, adding that although the situation is critical, there is nothing that says the process won’t reverse itself.
“If there was a summer which just wasn’t so warm, maybe with not so much cloud cover which promotes rapid melting, I think at the end of that summer the ice coverage could be much bigger, which could start a reverse feedback,” said Haas. “I think this is possible.”