DATE=9-30-02

TYPE=English Programs Feature

NUMBER=7-37903

TITLE=Arctic's Largest Ice Shelf Breaks

BYLINE=Rosanne Skirble

TELEPHONE=(202) 619-2806

DATELINE=Washington

EDITOR=Rob Sivak

CONTENT=

Attention: Environment

INTRO: In 2002 a massive ice shelf in Antarctica collapsed into the sea and shattered into thousands of icebergs. Scientists attributed the collapse to a rise in temperatures in the Earth's South Polar Region over the last fifty years. As VOA's Rosanne Skirble reports, similar events are taking place at the other end of the world, too.

TEXT: The Ward Hunt Ice Shelf is the largest ice shelf in the Arctic Ocean. Now it has broken and scientists who have studied the event say it is evidence of accelerating climate change in the world's North Polar Region.

The ice shelf rupture caused the immediate draining of a freshwater lake trapped behind the ice shelf. The loss has affected a unique biological ecosystem of both fresh water and marine species of plankton and microscopic animals and algae that live on the upper ice surface.

Warwick Vincent is part of a team of researchers from Laval University's Center for Northern Studies in Quebec and the University of Alaska who have documented the breakup.

He says the ancient ice shelf is an important feature of the Arctic environment.

AUDIO CUT: WARWICK VINCENT

"As a biologist I have been especially interested in the life forms that have been associated with these icy habitats. It is a fascinating place to find communities that are living right at the very edge of existence. Some of the early steps of the evolution of life are believed to have taken place at times when there were periods of major freeze up.

It is like a time machine in some respects to look at these primitive communities (with) microscopic algae, microscopic plants and even little animals.

But in fact, they produce something that is visually obvious. In these vast expanses of white and rolling terrain, suddenly there will be a huge area bright orange looking like some alien life form has appeared, but in fact it is this microbial life that has adapted to these very severe conditions.

The ice acted as a kind of a dam across a fjord. And so the surface layer was fresh water. The melt water coming in was dammed behind this ice shelf and then gradually seeped out from under this ice shelf into the ocean."

RS: "What have you observed in this region."

WV: "We've been monitoring this set of environments for about ten years, but with comparisons back in time. And, our first analysis suggested that there was not very much going on. The overall extent of the ice was about the same as the 1980s.

On the other hand when we went back into the early literature, in fact going all the way back to Commander Perry, when he did his North Pole expeditions. We found that this very thick ice, with its characteristic undulating surface was very much larger, perhaps ten times larger than it is today.

So, we started looking at changes in this ice feature. We knew that it was a feature that dated back 3,000 before the present and so any changes in this environment would indicate substantial changes in the local environment."

TEXT: Warwick Vincent says the scientists followed the decline of the ice shelf between 2000 and 2002 using site visits, RADARSAT imagery and helicopter over flights.

AUDIO CUT: WARWICK VICENT

"Essentially the ice shelf had completely broken into two with the associated fractures and the calving of large ice islands that were starting to move out into the Arctic ocean. Subsequent to that we have been looking very closed with expeditions to the region to measure down through the cracks and to determine how large they are and whether they extend to the ocean. And (we have) confirmed that substantial fragmentation has taken place."

RS: "Where is all this ice going?"

WV: "That's a good question and at the moment most of the ice is still within the original embayment. This is about 400 square kilometers of ice. But there are sections of this that are moving out, and the experience from the past is that some of that would move eventually out to the Beauford Sea, in the West Arctic region and towards Alaska. And, so from that point of view there are concerns regarding shipping, and drilling platforms, although now with these very high technology satellite systems, it will be possible to monitor even very small pieces of this ice shelf."

RS: "What caused the cracking and collapse in the ice shelf?"

WV: "Our first inclination was that this was something associated with the local temperature. We installed an automated climate station on this ice shelf. (And) we started making correlations between that ice shelf data that were around. There was a military station called 'Alert' where a very nice data record was available. From that we were able to cross correlate and really reconstruct the temperature changes, and we see in fact over the last three decades a very substantial, highly significant increase in local air temperatures in this region. (This is) in fact in the same order of the temperature increases that have been seen in west Antarctica where ice shelves are now known to be breaking up."

RS: "So, you would attribute it to global warming?"

WV: "At this stage we can't make the link directly to global warming. We see this strong correspondence with a regional warming trend, but we really just don't have the data or the mechanistic understanding of this complex phenomenon to be able to pin point this to an overall increase in temperature on a planetary scale. However it should be said that it is consistent with all the predictions of global warming which identified this northernmost region of the northern hemisphere to be the most sensitive to future change."

RS: "As you mentioned a massive ice shelf in Antarctica collapsed (March 2002) and fell into the sea and broke into thousands of icebergs. How does what is taking place in the Arctic mirror that event?"

WV: "Well I think that there are similarities and there are differences. In the Arctic the ice shelves are of a much smaller scale. This was the largest ice shelf and a substantial piece of ice, but still small relative to the vast ice shelves occurring in Antarctica. Secondly, in Antarctica the ice shelves are fed by glacier input, which gives them a little bit more reservoir of ice input and a little bit more inertia in some respects. On the other hand in Antarctica these ice shelf collapses have been identified as indicators again of regional climate change because there is so much uncertainty to link this to a global picture. But, increasingly it appears that these ice shelves both in Antarctica as well as in the north Polar region are centennials of major climate change that is taking place."

RS: "What is major take-home message? Why is the collapse significant?"

WV: "I think that the primary message is the Arctic is warming. In the past we have seen some increases in temperature in the Arctic, in the western side in Alaska, for example and changes in Siberia. We have tended to think of the Eastern Arctic as kind of apart and (that it) has really avoided these temperature changes. What we are now seeing is more of a circumpolar effect which is increasingly bringing us to the point of view that in fact the Northern Hemisphere in general is changing."

TEXT: Warwick Vincent from Laval University and colleagues will report their findings on the effects of climate change on the Arctic ice shelf in an upcoming issue of Geophysical Research Letters. (SIGNED)

NEB/RS