Radio Script
2003

Scientists say large cracks in Canada's massive Ward Hunt Ice Shelf are a sign of a warmer Arctic climate. (Courtesy Derek Mueller, Laval University, Québec, Canada)

Past Tense Ice
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INTRO: Some of the thickest and oldest ice in the Arctic Ocean is disappearing. As it melts, it's changing the Arctic environment in profound ways. Doug Schneider has more in this week's Arctic Science Journeys Radio.

STORY: Scientists in Canada and the United States announced recently that one of the largest ice shelves in the high Arctic—the Ward Hunt Ice Shelf on the north coast of Ellesmere Island in Nunavit, Canada—had quite literally cracked up, causing a large freshwater lake trapped behind it to drain into the Arctic Ocean. Martin Jeffries is a scientist at the University of Alaska Fairbanks and an author of a recent study of the ice shelf.

JEFFRIES: "We observed the formation of a series of extensive fractures in the Ward Hunt Ice Shelf. By extensive, I mean they stretch many kilometers and they extend from the top to the bottom of the ice shelf."

For the past 3,000 years, the Ward Hunt Ice Shelf has remained intact and in place. Covering an area of the Arctic Ocean about the size of Chicago, the ice shelf is about 40 meters or 120 feet thick.

	This satellite radar image shows a large fracture splitting the Ward Hunt ice shelf from roughly north to south. (Courtesy Canadian Space Agency and the University of Alaska Fairbanks Synthetic Aperture Radar Facility) Click image to view larger version.

Jeffries and Canadian colleagues Warwick Vincent and Derek Mueller of Laval University in Québec reported recently in the journal Geophysical Research Letters that the Ward Hunt Ice Shelf had split in half and calved a number of ice islands.

The fractured ice shelf is just the latest in a series of events scientists say offer tantalizing clues that a warmer Arctic climate is having real consequences on the region's fragile environment.

JEFFRIES: "It's certainly the largest and most significant ice shelf event on Elsemere Island that we've seen in 40 years. In a larger context as evidence for Arctic change, certainly I would rate it up there as one of the largest and most significant."

Martin Jeffries says that even before fractures appeared in the ice shelf, the shelf and surrounding sea ice had become steadily thinner in recent decades. Josefino Comiso is a NASA climate scientist who uses satellite data to measure the extent of ice all across the Arctic Ocean. He says the extent of so-called perennial sea ice—that's ice that doesn't melt during the warm summer months—has shrunk significantly since the late 1970s, and could be all but gone by the end of the century.

These images show decreasing thickness and extent of Arctic sea ice from January 1, 1990, and January 1, 1999, respectively. The images were created using data from the Defense Meteorological Satellite Program's Special Scanning Microwave Imager. (Courtesy NASA) Click images to view larger version.

COMISO: "If you look at the perennial ice cover alone, the extent of that total area is shrinking by almost ten percent per decade."

Comiso says the thick, year-round sea ice and ice shelves are important to the Arctic's climate. In the summer, the ice reflects the sun's warmth back into space. But if the ice melts, the solar energy would be absorbed into the ocean, warming the water that in turn would melt even more ice.

Sea ice ecologist Rolf Gradinger from the University of Alaska Fairbanks says the absence of sea ice could have impacts on everything from algae to polar bears.

GRADINGER: "For many of these Arctic species, they only exist related to ice. So when the ice environment is gone, these species will basically disappear. And these are pretty important species for the Arctic food web. When you think of the food web for the central Arctic Ocean, the main source of food for animals is produced within the ice by small micro algae. They grow within the ice and produce 50 to 60 percent of the total organic carbon in the central Arctic Ocean. There are small crustaceans, we call them amphipods, that feed on this ice algae. Amphipods are the major food source for fish species, such as arctic cod. That again is the main source of food for the ringed seal and the spotted seal, which is the major prey of polar bears."

While few scientists disagree that the Arctic has warmed several degrees in recent decades, the jury remains deadlocked as to whether natural forces or human dependence on greenhouse fuels such as gas, oil and coal are to blame. Mark Serreze is a research scientist at the University of Colorado Boulder and the National Snow and Ice Data Center.

SERREZE: "When we look at the Arctic we see that it has shown very strong warming for at least the past 30 years. But whether this is a global warming signal is not altogether clear, because much of this warming is actually due to a change in the circulation of the atmosphere."

Serreze says the changes seen in the atmosphere may or may not be the result of human activities.

This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences. I'm Doug Schneider.

Thanks to the following individuals for help preparing this script:

Josefino Comiso
NASA
Goddard Space Flight Center
Greenbelt, Maryland
Phone: 301-614-5708
Email: comiso@joey.gsfc.nasa.gov

Rolf Gradinger, Biological Oceanographer
Institute of Marine Science
University of Alaska Fairbanks
Fairbanks, AK 99775-7220
Phone: 907-474-7407
Email: rgradinger@ims.uaf.edu
Web Profile: http://www.sfos.uaf.edu/directory/faculty/gradinger/

Martin Jeffries, Research Professor
Geophysical Institute
University of Alaska Fairbanks
Fairbanks, AK 99775
Email: Martin.Jeffries@gi.alaska.edu
Phone: 907-474-5257
Web Profile: http://www.gi.alaska.edu/remsense/personal/mjeffries.htm

Mark Serreze, Research Associate
Cooperative Institute for Research in Environmental Sciences
University of Colorado at Boulder
216 UCB
Boulder, CO 80309-0216
Phone: 303-492-2963

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Related websites

NASA Earth Observatory News

"Arctic Perennial Sea Ice Could Be Gone by the End of the Century," NASA Goddard Space Flight Center

Geophysical Research Letters

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