Leanne Bulger extends a plastic pipe into a hole in the ground possibly caused by thawing permafrost. The pole reached 13 feet before striking the bottom of the cavity.
Leanne Bulger recently found a new hole in the forest floor on the west end of Fairbanks. Into it, she poked a long plastic pipe.
“Thirteen feet,” she said when the pole finally hit ground she could not see.
Bulger, an undergraduate student at the University of Alaska Fairbanks, had hiked to the northeast corner of the campus’s thousand-acre wood on a late April day. Six other researchers accompanied her to check out this odd feature of the landscape.
One year ago, Bulger first visited a hole in the forest floor that seemed to be exhaling. The force and moisture content of that cold breath was so consistent during the previous winter that the hole had built its own little chimney. It looked like a snowman.
After receiving a tip from a nearby homeowner (me) who had watched the chimney grow over the winter, Bulger adopted the site as her own research project. Her project mentor, Go Iwahana of the International Arctic Research Center, insisted she follow her interest and provided her with equipment to learn more.
On the recent morning a year after her first visit, Bulger staged what she called a “geosciences jamboree” with her colleagues.
The April day was just warmer than freezing, with two sandhill cranes croaking overhead as they returned from a winter away. Earthy-smelling ground emerged in patches, but the shrinking snowpack still covered much of the landscape.
With a king-size power drill, a few of the half-dozen scientists Bulger invited extended the depth of a borehole to 15 feet beneath the ground surface. They then pushed thermistors into a plastic pipe they had slipped into that 15-foot hole.
Initial temperature readings confirmed the ground had remained unfrozen at levels deeper than the seasonal freeze of the first five feet during the past winter. That meant this landscape where permafrost existed in the recent past was now free of the frozen ground that had persisted for perhaps thousands of years.
Last September, Bulger used a portable gas analyzer in the original fist-size chimney hole. She found that the ground there was exhaling carbon dioxide at a concentration more than 50 times greater than the free air above the hole.
She visited the site all winter, twice each month hiking out with the 30-pound gas analyzer on her back and dragging a sled of supplies. Even at the darkest coldest time of the year, the readings were still 10 times higher than the air above the hole.
“It’s really strange that one small spot is pushing out so much CO2,” she said.
The stream of carbon-dioxide rich air is possibly the collective breath of microorganisms now freed from eons of being frozen. They may be feeding on the newly available carbon stores of the boreal forest floor. It is also possible that the CO2 might be leaking upward from very deep thawing permafrost deposits.
As the climate continues to warm, that exhaling CO2 scenario is playing out, invisibly, all over Alaska.
The larger picture intrigues Bulger, who has a few times presented a poster with her findings and photos of the UAF campus site.
During those presentations, people told her of sinkholes or depressions in their yards, possibly from the thawing of ground that had been frozen for thousands of years.
“People in the community seem surprised, which tells me it’s a recent development,” she said.
More and more people are now seeking Bulger out to ask about the phenomenon.
“Now I’m the ‘Hole-in-the-Ground Girl,’” she said.
On that recent day in the woods, two of her colleagues pulled a sled over the ground to measure the subsurface with ground-penetrating radar. Another inserted a camera into the original hole, finding winged insects crawling deep within the dark and CO2-rich space.
Bulger wants to return after the snow melts to fly drones over the snowless forest floor to make a precise map of how the land looks now (and how it may sink in the future). And she has applied to a graduate program at UAF, one where she may take an even deeper look into the mysterious hole in the ground that is likely one of many developing all over Alaska.
She knows one of her biggest challenges in her new graduate study will be to focus on one aspect that interests her.
“I started asking just a few questions,” she said. “But now I have about 18,000.”
Since the late 1970s, the University of Alaska Fairbanks’ Geophysical Institute has provided this column free in cooperation with the UAF research community. Ned Rozell is a science writer for the Geophysical Institute.
