Anchorage Daily News

FAIRBANKS -- Interior Alaska's permafrost has warmed in some places to the highest level since the ice age ended 10,000 years ago, its temperature now within a degree or two of thawing.

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Earth frozen since woolly mammoths and bison wandered Interior steppes has been turning to mush. Lakes have been shrinking. Trees are stressed. Prehistoric ice has melted underground, leaving voids that collapse into sinkholes.

Largely concentrated where people have disturbed the surface, such damage can be expensive, even heartbreaking. It's happening now in Fairbanks: Toppled spruce, roller-coaster bike trails, rippled pavement, homes and buildings that sag into ruin. And the meltdown is spreading in wild areas: sinkholes, dying trees, eroding lakes.

These collapses bode ill: They are omens of what scientists fear will happen on a large scale across the Arctic if water and air continue to warm as fast as climate models predict.

"So far, we have only some local places where permafrost is thawing naturally," said expert Vladimir Romanovksy, a Russian-born geophysicist at the Geophysical Institute of the University of Alaska Fairbanks.

"But we are very, very close to this point when it (all) starts to thaw."

After record high temperatures during the summer of 2004 and last winter's deep insulating snow, Romanovsky said he expects Interior permafrost will again be significantly warmer than normal this year -- still closer to melting.

The Geophysical Institute and Romanovsky maintain the world's most extensive network of permafrost "observatories" -- basically thermometers sunk deep into the frozen earth, many along the trans-Alaska oil pipeline. What they report is disconcerting.

Permafrost is shrinking: warming on the bottom from the Earth's natural heat, warming on the top because of air temperature and deep snows.

It's like holding an ice cream sandwich in your hand on a sunny day. While the icy center stays hard, it shrinks as the top and bottom both melt.

"Our permafrost is still stable, even though it is very, very warm," Romanovsky said. "But the moment it starts to thaw, we will be able to say we are the warmest we have been the last 100,000 years."

For a glimpse of that future, look no farther than the hills north of Fairbanks, near where Romanovsky lives with his wife and two of his three sons.

In a meadow on his mother-in-law's property, weird six-foot-deep channels and holes crisscross the ground, trenches and bomb pits from what amounts to thermal warfare.

A small hole opened up in the sod a few years ago, curving down into the earth like some gopher den. This spring, his sons and other children playing near the house discovered the bottom had fallen out. The cavity was now large enough to bury a person. No one has crawled down to see where it ends.

Romanovksy discourages his sons playing in the field. "It is not safe," he said.

Maybe 100 yards away, other sinkholes have formed along the shoulder of Goldstream Road, the main travel route for residents of the rural valley. Romanovksy took photos of his sons by one hole in 2001 and matched them to another set taken this spring. In the successive snapshots, the boys grow taller, the hole grows deeper.

The newest chasm -- maybe 10 feet across -- had been filled with gravel by highway crews. But only a few weeks later, concentric cracks circled a depression. It looked like a bull's eye.

As it does every summer, the hole was collapsing again.

'FROZEN DIRT' NOW GLAMOROUS

Romanovsky is part of a small army of scientists investigating Arctic climate change. He teaches UAF college students, conducts research with the International Arctic Research Center and hopes to expand ground frost monitoring to other parts of the world with a grant from the National Science Foundation.

Since emigrating from Moscow in 1990, Romanovksy has found that Fairbanks offers a kind of paradise for a family man/permafrost scientist -- a middle-class paycheck in a small town surrounded by frozen ground.

Now 51 and a naturalized U.S. citizen, he still has a bulldog build from his days as a hockey defenseman for Moscow State University. He has two Ph.D.s, with training in mathematics, geology and the physics of how frozen dirt sheds heat.

Permafrost experts once labored in obscurity, he said. Graduate students were drawn to more glamorous topics, like glaciers and sea ice.

After all, he said, "permafrost is frozen dirt."

But the importance of permafrost as an indicator of climate change -- and the realization that its thaw could alter the northern landscape and release vast stores of greenhouse gases into the air -- has ignited huge interest.

"It's just exploded since last year," said Romanovsky, who starred in a recent New Yorker piece on global warming. "I'm going to have to stop giving interviews."

Permafrost degradation is only one element in a climate shift well under way. Overall, during the last half century, the Arctic has been warming much faster than the rest of the world. Alaska's average annual air temperature has increased 3.3 degrees between 1949 and 2003, with some areas rising almost twice as much, especially in winter and fall, according to the Arctic Climate Impact Assessment published last fall.

The most obvious signs are shrinking sea ice, melting glaciers and the thawing trend in permafrost, said Syun Akasofu, director of the Arctic research center, in a briefing this spring with Floyd DesChamps, a staffer of the U.S. Senate Commerce committee.

While warming is definitely happening, the causes remain unclear. Natural climate cycles that reach back thousands of years and greenhouse gases released by human activity both appear to be driving the warmth. But researchers still do not know which factors contribute more, Akasofu said.

Romanovsky warns that, whatever the reason, permafrost is easing closer to the thawing point across Interior Alaska. Will spruce forests transform into grassland? Will roads, buildings and pipelines collapse? Will Alaskans be forced to spend millions repairing damage?

One thing is certain, he said. "The permafrost we have was established during the last ice age, and now it's deteriorating."

TUNNEL TO THE PAST

On Alaska's North Slope, permafrost remains up to 1,000 feet thick in some places, underlying the landscape like an impermeable slab of bedrock that keeps the tundra saturated by preventing meltwater from draining off into the ground. Around Fairbanks, deteriorating permafrost has produced a different story, an underground drama of oozing and seeping, mostly invisible to people on the surface.

But there is a place where students and scientists can visit what remains of the ice age: a tunnel 10 miles north of Fairbanks that bores about 360 feet into a hillside off the Steese Highway near Fox.

Excavated in 1963-64 by U.S. Army engineers and researchers from the Cold Regions Research and Engineering Laboratory, the tunnel extends through ground that froze 20,000 to 40,000 years ago. The entrance emerges from the base of a steep, forested slope on the edge of a graveled field. Rather than a gateway to prehistory, it looks more like a weathered shack that got half-buried in an old landslide.

Visitors don hard hats because chunks can fall from the ceiling. During a spring tour, UAF geology professor Sarah Fowell instructed everyone to pick up their feet to keep from stirring the prehistoric silt that coats every surface. At the minelike portal, over the sound of refrigerator compressors, the cold airs smells like rotting flesh, like walking into a rancid meat locker. It's the bits and bones of prehistoric bison and mammoths, stuck in the walls.

"Thawing 12,000-year-old mammals -- it's not a good thing," Fowell said cheerfully. "Don't worry. You'll get used to it."

Along dusty walls stained with patches of white mold and protruding ice hang faded signs. They point out exotic highlights: a 14,000-year-old bone here, a clump of 30,700-year-old "fine fibrous organics" there.

Ice laces the ceiling. From a nearby wall, a pond that froze solid about 30,000 years ago bulges, buried by wind-blown silt. But let that pond melt and a 20-foot-deep sinkhole might collapse overhead.

WHEN THE BOTTOM FALLS OUT

Things keep sinking around Fairbanks.

When UAF crews began a parking lot for a new building behind the Geophysical Institute, Romanovsky warned them the area was undercut with voids and ice. The parking lot went in anyway. New sinkholes emerge each spring.

Bike trails ripple like roller coaster tracks. Houses have shifted, forcing a few people to move out or tear down. State officials blame rising maintenance costs throughout the Interior and Copper Basin on deteriorating permafrost and erosion, and Alaskans are already spending thousands of extra dollars on potholes and new pavement each summer. Sometimes the damage gets personal.

One sight Romanovsky visits every couple months is Ruth Macchione's sinking log cabin, with its sweeping view of Goldstream Valley and a green meadow.

Macchione's husband, Peter, built the 26-by-16 structure almost 50 years ago from birch logs cut off their homestead. Over the decades, they raised nine children, gardened, kept cattle and staked a team of sled dogs.

But at some point, the basement's foundation began to thaw previously frozen earth a few yards beneath the cabin's eastern wall. Bit by bit, the Macchione family home canted two feet off plumb. Basement windows started to submerge.

"It was getting pretty bad," Macchione said. "I had to block up everything -- block the stove, block the table, block the refrigerator."

The cabin outlived Peter, an aircraft mechanic who died in 1987 and is buried by the trees beyond the garden. Ruth stayed until 1999, then moved into a new log home on concrete piers. Water in the basement convinced her.

"It was coming from beneath," she said. "All I knew is I had to get out of there."

Romanovksy heard about Ruth's cabin a few years ago. He knocked on her door and asked if he and other scientists could visit every now and then. They talked for hours. She calls him a "mad Russian scientist."

Even after five years, she mourns the cabin built by Peter. She has no plans to tear it down. Perhaps someday, she said, her sons will put it on a new foundation. Perhaps there's a way to overcome the damage caused by the melting underfoot.

"You just get sick after doing all that work," she said.

The cabin's collapse is just a warning for other northern people, Romanovsky said -- of what might happen to pipelines, buildings and roads when the Arctic's bottom gives way.

Daily News reporter Doug O'Harra can be reached at do'harra@adn.com.