LiveScience.com Yahoo News 20 Apr 11;
A glacier range the size of the state of New York surprisingly contributes 10 percent of the world's melting ice, making it a primary contributor to rising sea levels.
"The Canadian Arctic, which we previously thought wasn't contributing very much to ice loss, has actually become one of the largest contributors," said study researcher Alex Gardner at the University of Michigan. "Most of the world's fresh water is stored in these glaciers and caps, and they are one of the primary drivers of sea level change."
Researchers have been watching this glacier range in the Canadian Arctic Archipelago for decades, but because of its remote location they weren't able to get accurate readings of how much it was being affected by the gradually increasing temperatures, particularly in summer, attributed to global warming.
NASA, in making ice loss estimates in the early 1990s, had determined that the glacier had been losing volume. Gardner looked at more recent changes: during the years 2004 to 2009. Over that study period, he found, the glacier lost a volume equivalent to about 75 percent of Lake Erie, the majority of that loss happening between 2006 and 2009. In these years, the loss was four times what it had been in the late 1990s.
Studying remote glaciers
The Canadian Arctic Archipelago includes thousands of islands covering 550,000 square miles (1.4 million square kilometers), nearly the size of Alaska. It is home to one of the largest freshwater glacier ranges on Earth, which has 3½ times the volume of the combined Great Lakes.
To test how much ice these glaciers were losing, Gardner's team created a computer model and used climate data from 2004 to 2009. They noticed this dramatic loss of ice and called colleagues to confirm their findings.
A team from Trent University in Ontario, working with the ICESat, a NASA satellite that can measure elevation using a laser beam from space, confirmed Gardner's findings that the glaciers had been losing volume. A third team, working with the GRACE satellite, a joint venture between NASA and the University of Texas, also confirmed the findings.
GRACE works to measure the tiny gravity fields created by these massive blocks of ice. Over time, as the glaciers lose volume, their gravity decreases.
Slippery ice slope
With these findings, the archipelago snags third place among locations of the world's greatest ice loss, though it contains a very small portion of the world's land ice. The huge ice sheets covering Greenland and Antarctica, which contain 99 percent of the Earth's ice, also come in first and second place, respectively, in volume lost.
The archipelago — which makes up a third of the remaining 1 percent — is able to compete with these behemoths because it is in an area where a few degrees of temperature change can have a great effect on melt. Essentially it's not as cold there as it is in Antarctica and Greenland.
"The big ice sheets have large areas at high elevations and large areas that are very cold," Gardner said. "Despite their very large size, proportionally they experience less melt."
All of this water has to go somewhere, and it ends up in the oceans. "In winter these ice sheets don't melt at all, so it's very confined to summer months," Gardner said. "It's like a giant faucet turns on for two months, then shuts off." The fresh water in the glacier range is lost into the oceans and the sea level rises.
Gardner is currently working to apply his glacier melt model to go back in time, using historical climate data, to put this ice melt into a longer-term perspective on the health of the glacier.
Melting ice on Arctic islands boosts sea levels: study
Yahoo News 20 Apr 11;
PARIS (AFP) – Melting glaciers and ice caps on Canadian Arctic islands play a far greater role in sea level rise that previously suspected, according to a study published Thursday.
Between 2004 and 2009, the 30,000 snow-and-ice covered islands in the Canadian Archipelago shed 363 cubic kilometres (87 cubic miles) of water, equivalent to three-quarters of contents of Lake Erie, the study found.
During the first half of this six-year period, the average loss was 29 cubic kilometres (seven cubic miles) per year. But during the second three-year period, the average jumped to 92 cubic kilometres (22 cubic miles) annually.
Over the full six years, this added a total of one millimeter to the height of the worlds oceans, the researchers calculated.
"This is a region that we previously didn't think was contributing to sea level rise," said Alex Gardner, a researcher at the University of Michigan and lead author of the study.
"Now we realise that outside of Antarctica and Greenland, it was the largest contributor for the years 2007 through 2009. This area is highly sensitive and if temperatures continue to increase, we will see much more melting," he said in a statement.
Ninety-nine percent of all the world's land ice is trapped in the massive ice sheets of Antarctica and Greenland.
Despite their size, however, they currently only account for about half of the land-ice bleeding each year into the oceans, mainly because they are so thick and cold that ice melts only at their edges.
The other half of the ice melt contributing to sea-level rise comes from smaller mountain glaciers and ice caps such as those in the Canadian Arctic, Alaska and Patagonia.
The study's results, published in Nature, show that the impact of these regions on sea level rise has been largely overlooked.
Gardner cautioned that the relatively short time span of the study -- six years -- is not long enough to constitute a climate trend, but said the results should be taken as a warning.
"This is a big response to a small change in climate," he said. "If the warming continues and we start to see similar responses in other glaciated regions, I would say it's worrisome."
Most experts on climate change and sea levels project that the ocean watermark will rise roughly a metre by century's end.
This could be devastating for tens of millions of people living in low-lying deltas, many of which are also sinking at the same time.
Rising sea levels could poison aquifers and amplify the impacts of storm surges and tsunamis, experts say.
