Arctic's Biggest Ice Shelf, a Sentinel of Climate Change, Cracks Apart
The breakup is apparent evidence of global warming. It also has drained a freshwater lake containing a rare ecosystem.
The Los Angeles Times, Sept. 23, 2003
The largest ice shelf in the Arctic -- an 80-foot-thick slab of ice nearly the size of Lake Tahoe -- has broken up, providing more evidence that the Earth's polar regions are responding to ongoing and accelerating rates of climatic change, researchers reported Monday.
The Ward Hunt ice shelf, located 500 miles from the North Pole on the edge of Canada's Ellesmere Island, has broken into two main parts and a series of ice islands. A massive freshwater lake long held back by the ice has drained away.
"Large blocks of ice are moving out. It's really a breakup," said Warwick Vincent, a professor of biology at Laval University in Quebec and co-author of the report, which will be published in an upcoming issue of the journal Geophysical Review Letters. "We'd been measuring incremental changes each year. Suddenly in one year, everything changed."
While far larger shelves of ice have cracked off the edges of Antarctica, this is the largest ice separation in the Arctic, occurring in an area of the eastern Arctic long thought to be more protected against the gradual warming of the planet.
"This type of catastrophic [event] is quite unprecedented," said Martin Jeffries, a professor of geophysics at the University of Alaska Fairbanks and co-author of the report.
Because of their longevity and sensitivity to temperature, ice shelves are considered "sentinels of climate change." In recent years, scientists have seen ice shelves the size of Rhode Island break off of western Antarctica as it warms and have measured glaciers' retreat in response to warmer temperatures throughout the western Arctic.
Weather data recorded at the nearby military station Alert on Ellesmere Island show that temperatures there have been warming since 1967 at the same rate as in western Antarctica: about one degree Fahrenheit per decade. The average July temperature of recent years of 34 degrees was above the temperature 32 degrees at which ice shelves are known to break up.
The researchers said they considered the weakening of the ice additional evidence of climate change in the high Arctic and said the report fit with studies that show global warming trends are connected to the human production of greenhouse gases. Those trends have been seen first and amplified in the Arctic.
But they said other factors, including ocean circulation and atmospheric patterns that can last for decades, could be contributing to the changes in the ice.
"The picture is a little murky," Jeffries said.
Jeffries, who has worked on the region's ice sheets for two decades, said the ice appears to have thinned dramatically in that time. The Ward Hunt ice shelf was measured at 150 feet thick in 1980 and now appears to be less than half that in some places.
The ice shelf has lost 90% of its area since 1907, when explorer Robert E. Peary crossed it on his way to the North Pole and complained bitterly about its undulating terrain.
Researchers were lucky to catch the breakup in such a remote and relatively unstudied area. Derek Mueller, a graduate student of Vincent's, had reached the ice shelf by helicopter last summer to study the strange microbes living there when he saw that the massive cracks extended all the way through the ice.
Using a satellite phone, he called Vincent. Canada's RADARSAT satellite then captured fresh images of the ice shelf as it was breaking up.
Vincent is very concerned about the ecosystem he and his students were studying. It has basically been flushed out to sea. The weakening and cracking of the ice shelf allowed a freshwater lake that had been dammed behind the ice to drain suddenly.
The ice shelf kept about 140 feet of freshwater pooled atop 1,200 feet of denser seawater. The layers of fresh and salty water supported an ecosystem of strange microbes, or extremophiles, that are of particular interest to scientists trying to understand the limits of life on Earth and in outer space.
"The whole lake just drained. It just disappeared entirely," Vincent said. "We're at a point where we're starting to lose these unique cryo-ecosystems of the north before we can understand them."
Other researchers are concerned about the increasing amount of fresh water pouring into the Arctic Ocean from breaking ice shelves, melting glaciers and rain-swollen rivers.
Cold, salty water in the Arctic and North Atlantic oceans plays a major role in driving ocean currents that transport heat around the globe.
One of the most important of these is the Gulf Stream, which carries warm water up the East Coast of the United States and across the Atlantic to northern Europe.
In previous geological eras, warmer climates and the release of freshwater lakes that had been dammed by ice have caused this current to slow and shut down, drastically cooling parts of Europe.
A study in the journal Science in December reported massive amounts of fresh water entering the Arctic Ocean from Russia's largest rivers, due to increases in precipitation linked to warmer temperatures.
If temperatures rise globally by several degrees in the next century, as many scientists predict, increased river runoff, melting of glaciers on Greenland and melting of ice shelves "would bring us well within the range of what models say could be a serious disruption to ocean circulation," said Bruce Peterson, a senior scientist at the Marine Biological Laboratory in Woods Hole, Mass.
While the amount of fresh water released from the breaking of the Ward Hunt ice shelf is relatively small, some scientists say it is part of a larger pattern of freshening of ocean waters that could prove dangerous in the future.
"The question is, at what point do those currents become unhappy?" said Richard Alley, a professor of geosciences at Penn State University and an expert on ice sheets and abrupt climate change. "We're just not good enough to tell right now."Largest Arctic Ice Shelf Breaks Up, Scientists Say
WASHINGTON (Reuters) - The largest ice shelf in the Arctic, a solid feature for 3,000 years, has broken up, scientists in the United States and Canada said on Monday.
They said the Ward Hunt Ice Shelf, on the north coast of Ellesmere Island in Canada's Nunavut territory, broke into two main parts, themselves cut through with fissures. A freshwater lake drained into the sea, the researchers reported.
Large ice islands also calved off from the shelf and some are large enough to be dangerous to shipping and to drilling platforms in the Beaufort Sea.
Local warming of the climate is to blame, they said -- adding that they did not have the evidence needed to link the melting ice to the steady, planet-wide climate change known as global warming.
Warwick Vincent and Derek Mueller of Laval University in Quebec City, Canada, and Martin Jeffries of the University of Alaska Fairbanks lived at the site, flew over it and used radar satellite imaging for their study.
Writing in the journal Geophysical Research Letters, Vincent's team said all of the fresh water poured out of the 20 mile long Disraeli Fjord.
This in turn has affected communities of freshwater and marine species of plankton and algae, said Mueller, a graduate student who has studied the tiny creatures.
Only 100 years ago the whole northern coast of Ellesmere Island, which is the northernmost land mass of North America, was edged by a continuous ice shelf.
About 90 percent of it is now gone, Vincent's team wrote.
The area has been getting warmer, they said. A similar trend in the Antarctic has caused the break-up of huge ice shelves there.
"There's a regional trend in warming that cycles back 150 years," Mueller said in a telephone interview. "I am not comfortable linking it to global warming. It is difficult to tease out what is due to global warming and what is due to regional warming."
Records indicate an increase of four-tenths of a degree centigrade every 10 years since 1967. The average July temperature has been 1.3 degrees Celsius or 34 degrees F -- just above the freezing point -- since 1967.
Climate change has affected ocean temperature, salinity and flow patterns, which also influence the break-up of ice shelves in the Antarctic. "It's not just as simple as it gets x degrees warmer and the ice melts this much," Mueller said.
Warmer temperatures weaken the ice, leaving it vulnerable to changed currents and other forces.
The New York Times, Sept. 23, 2003
A large ice shelf that has jutted into the Arctic Ocean from northernmost Canada for at least 3,000 years has broken up over the last two years, providing fresh evidence that the region is warming past thresholds that can produce abrupt changes, scientists said yesterday.
The scientists, from Laval University in Quebec and the University of Alaska, Fairbanks, described the changes in a paper published in the Geophysical Research Letters.
The disintegration of the ancient ice shelf the largest in the Arctic appears to have been caused both by a century-long warming trend and, more recently, by an accelerated rise in temperatures, the researchers said.
They said it was not yet possible to say whether the melting was related to rising atmospheric concentrations of heat-trapping greenhouse gases from human activities. But they added that the breakup was just one of many signs of enormous climate shifts in the Arctic that merited careful monitoring.
"It is part of a long-term process, we believe," said Dr. Warwick F. Vincent, a biologist specializing in arctic ecology at Laval University and an author of the new study. "But the most recent changes are substantial and correlate with this recent increase in warming that we've seen from the 1960's to the present. It's an example where a critical threshold has been passed."
The other authors were Derek R. Mueller of Laval and Dr. Martin O. Jeffries from the University of Alaska.
The 150-square-mile region of floating ice, called the Ward Hunt Ice Shelf, had formed a cap across the mouth of the 20-mile-long Disraeli Fjord on Ellesmere Island, in Nunavut. That caused a rare condition in which a 140-foot-thick layer of fresh water accumulated atop the denser seawater in the 1,200-foot-deep fjord, forming an isolated floating freshwater lake.
The trapped fresh water harbored a unique ecosystem of rare plankton and other life that has collapsed now that its basin has broken up and the fresh water has flowed into the Arctic Ocean, Dr. Vincent said.
The ice of the Ward Hunt shelf is up to 100 feet thick, making it far larger than the 10-foot slabs of floating sea ice that form a milling cap on the Arctic Ocean.
The pieces could persist for many years as they start to drift in Arctic waters, the authors said. For the moment, they exist as free-floating jigsaw pieces, in part held near the coast by Ward Hunt Island. The island is a popular jumping-off spot for expeditions over the sea ice to the North Pole.
It was the last large remnant of a much more extensive shelf that once fringed all of Ellesmere Island, Dr. Vincent said. Over all, he continued, that fringe has shrunk by more than 90 percent over the last century.
Ellesmere's projecting ice shelves broke off at a rapid rate through most of the last century, but the erosion essentially stopped in 1982. The breakup of the last section, around the Disraeli Fjord and Ward Hunt Island, began in 2000, the researchers said, when big new cracks were detected in satellite images.Arctic ice shelf breakup reported
The Associated Press, Sept. 22, 2003
Warming conditions pushing average temperatures above freezing are being blamed for the breakup of an ice shelf at Ellesmere Island in northern Canada.
The breakup of the Ward Hunt ice shelf between 2000 and 2002 was reported Monday by researchers from Canada and the United States.
Calving of ice shelves into giant icebergs is seen regularly from Antarctica and many scientists believe that is caused by global warming, though research continues to try and verify that.
The similar ice breakup in the Northern Hemisphere was reported by Warwick Vincent and Derek Mueller of Laval University in Quebec City, Quebec, and Martin Jeffries of the University of Alaska, Fairbanks. Their findings are scheduled to appear in an upcoming issue of Geophysical Research Letters, published by the American Geophysical Union.
The researchers studied the ice both via satellite and through visits to the scene.
They reported that the ice shelves on northern Ellesmere Island had been stable since 1982, but in April 2000 a satellite revealed the first sign of cracking.
By 2002, observations from a helicopter showed that the fracture extended widely, breaking the ice shelf into two major parts and many smaller ones.
In July and August, 2002, the researchers landed to take measurements and found cracks that separated the central part of the shelf into free floating ice blocks. That August, the northern northern edge of the ice shelf broke free, they reported.
Besides freeing the floating ice blocks, the breakup caused the loss of almost all of the freshwater from a lake which had been dammed behind the ice in a fiord.
The scientists measured the temperature on the ice shelf in 2002 and correlated that with readings from Alert, about 109 miles away. Using the Alert records, they estimated that the ice shelf had an average annual temperature of 34 degrees Fahrenheit since 1967. Studies in Antarctica have shown a temperature of 32 degrees is critical to ice shelves breaking up.
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