Earlier this year, the geography of the Northwest Territories was altered in a subtle and bizarre way when a small, unnamed lake northwest of Fort MacPherson breached a wall of melting permafrost - and literally fell off a cliff.

Some 30,000 cubic meters of water drained out of the lake, saturating the ground below and causing mud and debris to ooze downstream for days.

Such "thaw slumps," caused when the permafrost is exposed to air and solar radiation, are common on the Peel River Plateau, but in recent years these events have become more frequent and intense, says Dr. Steve Kokelj, a permafrost researcher with the Northwest Territories Geological Survey.

A recent slump near the Dempster Highway released about 5 million cubic meters of debris -- three times the volume of the Rogers Centre stadium in Toronto -- into a valley.

Kokelj says while warming air temperatures are having an impact on the stability of the permafrost, of greater concern is the increasingly heavy summer rainfall in the region.

"Rainfall keeps the slopes unstable so these [permafrost] disturbances can grow for decades," he says. "They are certainly a consequence of a changing climate."

Kokelj, along with a number of other geologists and ecologists, are working with local communities to get a better grasp on the pace of permafrost thaw in the region and the possible consequences to western Arctic ecosystems.

"Communication between First Nations communities, land users and scientists, in terms of understanding northern environmental change, is a critical link," he says.