'Only wooden houses built before the 1950s will survive,' predicts Tatyana Botulo, a researcher at the only centre devoted entirely to probing the vast sheet of ice lying beneath about a quarter of the world's land surface.
The prognosis is gloomy. As global warming continues, by the year 2050 Yakutsk, the capital of a region twice the size of Alaska, risks sinking.
The problem with perma-frost, they say, is that it is no longer permanent.
But how fast is it melting?
The entrance to the Perma- Frost Institute is guarded by a concrete model of a mammoth. It reminds the 120 scientists who work here of what can happen when climates change. After the Ice Age Siberia warmed, its glaciers retreated and the mammoth became extinct.
The place is still murderously cold. The Arctic town of Verkoyansk registered the lowest temperature ever recorded in a settled area: 90.4F below zero. Even the warm areas of Yakutia, Sibera's biggest region, have a negative average temperature. The result is perma-frost, which in Yakutia covers an area twice the size of India. Its thickness ranges from only a few inches in the south to a mile in the Arctic settlement of Aikhan.
'The most important question now is how perma-frost thaws,' said Ms Botulo.
'Cities built on perma-frost risk destruction. We must take steps now to try and prevent this.'
The melting itself is not new. It is part of Siberia's annual cycle. Above solid perma- frost lies a so-called 'active layer'. It freezes in winter and thaws in summer, leaving pools of mosquito-infested water as a thin layer of frozen earth and ice nearest the surface dissolves. In Yakutsk, each street bears the scars of this summer sag, when the earth gets soggy and moves: concrete pavements buckle, roads crack and wooden huts and houses twist out of shape. This is Siberia's seasonal earthquake.
So long as settlers lived in log cabins this was not a problem. The ground moved, but rarely enough to cause serious damage. But in the 20th century Moscow, desperate to get at the diamonds, oil, gold and other minerals lying beneath the snow, began a mass settlement drive, building entire new towns in the world's most inhospitable region. The concrete apartment building that had already disfigured so much of the rest of the Soviet Union came to Siberia.
Faced with the problem of seasonally sagging ground, engineers came up with a solution elegant in its simplicity: the concrete pile. Instead of resting on ordinary foundations, apartments and factories were built on stakes set deep enough into the ground to penetrate beneath the 'active layer' and into perma-frost firmly frozen all year round.
Old settlements like Yakutsk exploded into cities. Entirely new towns sprouted across the tundra. The discovery of diamonds prompted Moscow planners to create a new city from scratch in 1955 at a place now called Mirny, which means 'Peaceful'. Further north still, on the Arctic Circle, appeared Udachny ('Successful'), the world's first town built entirely on concrete stakes.
Estimating the depth of the thaw zone has always beeen difficult. How much melts depends on the vagaries of summer temperature. But experts at the Perma-Frost Institute now see the whole process accelerating because of new, and mostly man-made, variables. Adding to general climactic change is a localised warming caused by water pipes, heating systems and other by-products of large-scale settlement. The critical boundary between solid perma-frost and the active layer is shifting.
Ms Botulo estimates that instead of starting only five feet beneath the surface, as it did when much of Yakutsk was built in the 1960s and '70s, the solid perma-frost needed to anchor a building will lie 16ft deep by the year 2050. This would leave most of the city built on piles too short to avoid the summer meltdown.
One technique employed to try and keep the earth frozen is to spike the ice with long metal pipes full of kerosene. This equalises temperatures and helps to keep the top layer cold. But there are calls for more radical solutions.
Svetlana Yarasova, chief city architect in the town of Mirny, thinks it is a mistake to keep transplanting blueprints from Moscow: 'We need our own style, that does not force us to fight so hard against nature.'Reuse content