Doug Ashbury
Northern News Services

NNSL (Jun 26/98) - Varied levels of permafrost lie beneath a quarter of the earth's surface.

But talk permafrost here and most Yellowknifers would point to something more surface-related -- our roads.

The city of Yellowknife is getting better, according to Hugh French, a leading permafrost scientist.

"I've just returned from a tour around town and it's fascinating to see how much geotechnical engineering there has been in Yellowknife in the past five to seven years put in place to combat heat," he said.

Among the example are thermosyphons and under-asphalt insulation. Thermosyphons, those tall tubes protruding from the ground -- there's one at the end of the legislature parking lot and a series alongside the Rockcliffe Apartments -- are passive heat-transfer devices which remove heat from the ground.

Carbon-dioxide gas in the above-ground portion cools and condenses in the winter, falling down the tubes to the underground portion. There it absorbs the earth's heat and rises, leaving the ground cold and preserving the permafrost.

Without the thermosyphons, building supports can sink and sag as the permafrost beneath them melts.

There are other examples of how construction techniques have resulted in deterioration of permafrost. French easily spotted a guard rail which had sunk dramatically.

The goal is to prevent heat from thawing the ground, French said. "Minimize thermal disturbance to the ground."

French was just elected president of the International Permafrost Association at the seventh International Conference on Permafrost. Conference sessions began Tuesday at the Explorer Hotel and wrap up Saturday with a tour of the BHP Ekati mine site.

The conference, held every five years, brings together permafrost researchers and engineers from around the world together to talk about the effects of ground that remains below 0 C continuously for at least two winters and a summer.

This year there are 250 delegates from 34 countries in attendance. Canada took the lead in forming the association through the National Research Council.

It is the first time the conference has been held in a city that actually has permafrost beneath its streets. Originally, when Canada won the right to hold the 1998 gathering, Ottawa was chosen as the host city, but a group of Yellowknifers successfully campaigned for a change of venue.

Permafrost research is attracting more attention today than ever, French said, thanks to climate change theories.

But when it comes to global warming, French said it is not sufficient to conclude that it means more melting.

"It's not that simple." More warming could mean more snow, he said, and more snow could insulate the ground against higher temperatures, resulting in more permafrost.

Aside from all the study, permafrost remains a financial challenge for those jurisdictions have to cope with it.