EUREKA, Canada — White-knuckle fliers plying the trans-polar commercial routes might be comforted to know about Eureka: This tiny Arctic scientific station and military outpost, perched on the shore of an ice-choked fiord in Canada's Northwest Territories, has a special "safety runway," long and strong enough to handle an emergency landing if a passenger jet ever got into trouble over these desolate wastes.

But the skittish air traveler might be somewhat less reassured had he witnessed a Eureka scene from the summer of 1988.

A Canadian Hercules transport plane, heavily laden with supplies for the secret military post farther north at Alert, came in for a routine refueling stop at Eureka. The gravel runway looked dry, but when the Hercules touched down, it sank up to its undercarriage in mud that appeared out of nowhere.

It turned out that the Arctic summer of 1988 was a relative scorcher, and the unusual heat had melted hidden ice deep within Eureka's soil. That left the seemingly dry "safety runway" floating precariously on an underground lake.

Unpleasant enough for the people who had to dig the huge air force plane out of the mud--but the freakish incident suggests even worse things to come.

"This sort of behavior could become more common if we have a number of summers like 1988," said Sylvia Edlund, a research scientist with the Geological Survey of Canada who happened to be studying the links between vegetation, soil dynamics and the climate near Eureka the day the plane made its belly-flop.

Many climate experts are convinced that the world is warming up, probably because of increased atmospheric levels of "greenhouse gases" given off by the burning of fossil fuels. The gases--carbon dioxide is the leading offender--trap heat close to the Earth's surface, much as windowpanes hold in a greenhouse's warmth.

If predictions of a "greenhouse effect" prove out, then global warming will hit the Arctic faster and harder than anywhere else on Earth. While the planet is widely expected to warm by about 3 to 5.5 degrees Fahrenheit by the year 2050, the Arctic is expected to warm by as much as 18 degrees Fahrenheit, particularly during the winter.

Such an Arctic thaw could devastate the fragile and little-understood ecosystems of the Far North. The undermining of gravel runways would be just one small piece of the picture. While no one can say with certainty just what an Arctic thaw would look like, scientists say it could involve anything from the demise of the mighty polar bear to a rise in sea levels and the inundation of dozens of Inuit, or Eskimo, villages that now cling to the Arctic coast.