UNH faculty member and glaciologist Mark Fahnestock recently made an important discovery, the end results of which are still very much unknown. Fahnestock co-authored a NASA-funded study that was published in the
Dec. 2 issue of the scientific journal "Nature." In it, he concluded that the world's fastest glacier, located in Greenland and known as the Jakobshavn Isabrae, has doubled its speed in the last six years.
The Jakobshavn Isbrae is also Greenland's largest outlet glacier, draining more than six percent of the country's total ice sheet area. As land ice is slowly pushed down toward the coasts, outlets such as the Jakobshavn Isbrae provide a passageway for it to make its way out to sea.
The importance of this outlet and his findings is that as more ice is transferred from land to sea, the overall sea level of the earth rises. Due to its recent speedup, the Jakobshavn Isbrae is now solely responsible for about four percent of the 20th century sea level rise. Because of this, the glacier is now providing important data relating to ice sheets, sea level rise and climate warming.
"We as glaciologists wouldn't expect to see this change occur so rapidly," Fahnestock said. "It tells us that big glaciers respond very quickly to a warming climate."
Fahnestock and co-authors Ian Joughin, a glaciologist at the Applied Physics Laboratory at the University of Washington, Seattle, and Waleed Abdalati, a senior scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., have been tracking the glacier since 1985.
Their research has been aided by satellites, aircraft and laser imagery from three different space agencies including NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).
According to Fahnestock, the global temperature has risen nearly two degrees since the 1980s. While this might not seem like a lot to most people, it can make all the difference in an ice-covered region such as the arctic.
"Ice acts as a reflector by bouncing back the sun's rays, which leaves very little sunlight to actually warm anything," explained Fahnestock. "But as the ice melts it opens up large areas of dark water which do absorb sunlight and as a result heat up."
Coupled with its recent acceleration is the fact that the glacier is also thinning, more than 30 feet per year since the last half of the '90s. As a result the mouth or, "tongue," of the outlet has been eroded to the point of disintegration, allowing for more icebergs to make their way out to sea.
"A lot of people thought that ice responded quite slowly to temperature change," Abdalati said. "And what this indicates is that it actually happens much quicker than expected.
"The warming that is happening to the waters there is certainly a prime contributor to the glacial thinning," he added. "It means this could certainly start to happen with other big glaciers as well."
The study's lead author, Ian Joughin, has been in Antarctica and could not be reached for comment.
With all this newly found data, however, there is still much more to be understood about glaciers and their responses to climate change before any real questions can be answered.
"We are still at the learning stages," said Fahnestock. "But we are much better than we used to be. We now know more than we ever used to because of satellites."
Nevertheless, the study illustrates that the Jakobshavn Isbrae has been doing anything but slowing down. According to their findings, the glacier went from a velocity of 4.2 miles per year in 1985, to 3.5 miles per year in 1992, and topped off most recently at 7.7 miles per year in 2003.
"In a warming arctic you would get responses like the ones we are seeing," Fahnestock said. "And the arctic is going to continue to warm up given what we already know about greenhouse gases.
"It would take thousands of years for them to melt, you would think," he said. "But if large glaciers continue to thin out like this, it is important to know what the ice sheets are going to do."
"We don't care what happens a thousand years from now," he added. "But someone will."
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