CHITINA (AP) -- Seeking clues into Alaska's climate change since prehistoric times and how it might relate to recent global warming, an international scientific team spent the past month drilling deep into ancient ice high in the St. Elias Mountains.
Working from a camp perched in a spectacular 15,000-foot-high saddle between Mount Bona and Mount Churchill, glaciologists from Byrd Polar Research Center at Ohio State University have so far extracted cores from a hole drilled more than 1,500 feet into the unnamed glacier.
''It's now more than 100 meters (330 feet) deeper than the deepest mountain glacier that they've ever drilled,'' said Anchorage-based geophysicist John Paskievitch last week.
Depending on the snowfall rate over centuries, this ice may offer a glimpse of the world more than 18,000 years ago, a time when glaciers covered much of the Northern Hemisphere.
Once analyzed in the lab, the trapped air bubbles and dust could yield unprecedented details about weather, volcanic eruptions and climate trends.
Paskievitch talks to expedition leader Lonnie Thompson once or twice a day by satellite phone. On Tuesday, after the drill had reached about 1,350 feet, Thompson was ''very excited and ecstatic about the depth,'' Paskievitch said.
The next night, Thompson reported reaching a pebbly rock layer some 1,509 feet down, possibly the deepest ice core ever drilled in a mountain glacier.
''They've bottomed out,'' Paskievitch said Thursday. ''They are collapsing camp and ... they're ready to come down.''
Using drills powered with solar panels and diesel generators, as well as hand augers, the scientists have cut several other holes, including one down to about 450 feet, Paskievitch said.
The ice cores have been sliced into hundreds of meter-long cylinders, each about 4 inches in diameter, then stored in insulated boxes buried at the site to stay frozen.
As weather permits, the cores are being flown to a freezer van parked at the state airport near Chitina, then later trucked about 4,000 miles across the continent to Columbus, Ohio, for analysis.
The goal will be to build a year-by-year timeline of temperature, snowfall, vegetation and atmospheric chemistry as written layer by layer in the ice between the two peaks.
''It's going very well,'' said Thompson, speaking during a brief, scratchy satellite phone conversation from the high camp. ''Everything has been ahead of schedule.''
But dismantling 6 tons of gear and two geodesic domes will require a daily dance around the volatile whiteout weather that can envelope 16,420-foot Bona and 15,638-foot Churchill with little warning.
Over the previous two weeks, glacier pilot Paul Claus of Ultima Thule Outfitters on the upper Chitina River was able to land at the camp only a few times in his 1,000-horsepower, single-engine, turboprop Otter. During one visit, he had to take off fast when thick clouds began to form.
''If I'd stayed five minutes longer, I'd still be there,'' Claus said a few days later.
The National Science Foundation is underwriting the roughly $450,000 project, with logistics from Veco Polar Resources. The Alaska Volcano Observatory and the National Park Service are helping out.
On mountain glaciers, each season's snowfall creates a new layer. If that deposit doesn't melt over the summer, it gets sealed in by the next winter's snow. As time passes, these deposits gradually compress into layers, like growth rings on a tree. This stratigraphic phenomena allows the layers to be dated and compared.
Thompson has spent 25 years creating a detailed climate record from the world's ice. He has led or joined 43 previous expeditions to the globe's frozen places, pioneering drilling techniques in remote camps in Peru, Kyrgyzstan, China, Africa and the Russian Arctic. His wife, Ohio State geography professor Ellen Mosley-Thompson, has led a series of her own expeditions, concentrating on the polar regions.
''He's put this really solid climate history picture together from data collected from ice cores all over the world,'' said Paskievitch, a seismologist with the Volcano Observatory who's worked on ice-coring expeditions to Antarctica. ''There are global climate issues and regional climate issues. ... To get the full global perspective, you need to get these data points around the globe.''
As a result, the OSU Ice Core Paleoclimatology Group has created a library of ancient climate. Nearly two linear miles worth of cores can be stored as cold as minus-40 degrees on racks in two giant freezers. Scientists remove the cores one at a time into sterile work rooms heated to about 14 degrees to perform sophisticated measurements.
Taken as a whole, this information may hold clues into one of the leading environmental puzzles of the age -- why Earth's atmosphere is heating up. Many scientists believe that this warming will ultimately trigger catastrophic shifts in ecosystems and agriculture.
Global average temps have warmed about 1 degree Fahrenheit since 1950. Parts of Alaska, Canada and Russia have warmed even more, about 3.6 degrees Fahrenheit, according to Thompson. Permafrost has begun to melt, and sea ice has shrunk.
Is this warming part of a natural cycle? Or has it been made worse by people burning fossil fuels that increase the concentration of greenhouse gases in the atmosphere?
Part of the answer may lie in a place known among mountaineers for its hurricane-force winds and tent-crushing blizzards: The saddle between Bona and Churchill.
They're drilling in such a difficult place because it's cold there -- so cold that it might not ever melt during the brief summer.
''They need very cold stable conditions, and they also need the stablest ice pack,'' said Paskievitch. ''So they want to go to an area where you don't get a lot of loss over the summer from the heat . . . They really don't like losing years.''
Using high-altitude helicopter and Claus' Super Otter, a 10-member team flew into the area in early May, first spending a few days acclimating at a lower elevation on the Klutlan Glacier. By the first week of May, they were on site, drilling toward a bedrock base that initial radar surveys suggested was only about 1,080 feet down.
By the last week in May, several team members had come down. The ice cores retrieved so far had been exceptionally clear, with little trace of dust or layering. But at least three faint discolorations suggesting volcanic eruptions had been found, Paskievitch said.
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