Thawing Permafrost in the Arctic Will Speed Up Global Warming
There's more carbon locked up in the high north's permafrost than the combined total released into the atmosphere by humans. The big melt going on right now in the Arctic could trigger a train of catastrophic events across the world.
While Bret-Harte studies how fire changes the makeup and abundance of plant species, Adrian Rocha is exploring the carbon balance. Rocha, a physiological ecologist at the Marine Biological Laboratory, has installed equipment in severely and moderately burned areas, and in an undisturbed area, that records carbon dioxide flux, among other data. He found that the most severely burned tundra emitted roughly twice as much carbon as undisturbed tundra typically absorbs. Mack, who's also working on the fire project overseen by Shaver, calculated that the fire consumed as much as the top 20 centimeters of organic soil, and that the carbon in that material was, on average, 35 years old. Initially, the researchers thought the carbon released by the fire might have been hundreds of years old, so the fact that it had been pulled out of the atmosphere only about a quarter-century ago was surprising, says Mack. "That made me think, maybe these tundra systems are more resilient than we think."
Still, warmer, drier summers and more shrubs will likely mean more fires. And just two years after the Anaktuvuk River fire, the researchers are already witnessing major changes in the burn sites. "We're seeing all these thermokarsts out there," says Bret-Harte. "Disturbing the surface that much, as you do with a burn, and making it black and absorbing radiation, is bound to make a lot of ice start to melt."
As the Arctic heats up and permafrost thaws, nutrients are seeping into waterways. Combined with warmer, drier, longer summers, these changes could spell trouble for aquatic dwellers. Parking a 14-passenger van laden with waders and equipment to tag fish, biologist Linda Deegan hops out and exclaims, "Look, it's a glaucous gull!" pointing to an enormous white bird with perhaps a five-foot wingspan tracing the S curves of the Kuparuk River. "Maybe the grayling are here." For 20 years Deegan has been charting their spring and fall migration. Closely related to salmon, Arctic grayling winter in lakes or rivers that don't freeze solid, then head to shallower streams in the spring to spawn.
Like Shaver did with his vegetation plots, Deegan's team, starting in 1985, manipulated the aquatic ecosystem, dripping phosphate into a section of the Kuparuk. The fertilizer fostered more aquatic plants, which supported more insects and thus provided more for the grayling to feed on. So grayling could benefit from bursts of nutrients that drain into waterways after fires. But Deegan doesn't expect that to happen in the long run.
Along with fertilizer, fires and thermokarsts dump sediment into waterways, potentially smothering aquatic life. Even if insect populations grow, their hatches and grayling migration--which may be cued by light, not temperature--might be thrown out of sync, leaving the fish little to eat. And as the region heats up, water bodies will warm; if water temperatures rise too much, the cold-loving grayling "shut down," says Deegan. "They become lethargic and just settle on the bottom and won't move, even if there's food available." If droughts become more prevalent, as predicted, stream sections could dry up, stranding the fish. That happened on the Kuparuk in 2003, and the grayling population Deegan has been studying for two decades still hasn't recovered. Before the drought, in a typical two-week window during fall migration, her team would count between 3,000 and 5,000 individuals. In 2009 they counted only 315. "I think my poor grayling are in deep trouble," says Deegan.
The animals that depend on grayling could face their own crisis. Lake trout devour grayling in mountain lakes. Grizzly bears, hungry after the long winter, dine on grayling in the spring. At that time of year the fish are also a staple of Native Americans' diets. Plummeting grayling numbers could hurt fish-eating migratory birds, too, including red-throated loons and red-breasted mergansers. The grayling's plight in the Kuparuk serves as a good barometer for other Arctic populations, says Deegan. "Grayling are the dominant freshwater fish around the pole. I'm sure there are places with populations that are doing fine. But we don't think this is restricted to just the Kuparuk. We have evidence from another stream in the same region where this habitat fragmentation and separation from overwintering areas has been happening because of drought."
The vastness of the tundra is nearly overwhelming from the air. Rising from the helicopter landing pad at Toolik, I look out on the rolling hills and braided waterways. After a few minutes, any signs of human presence disappear. I'm struck by how our influences from far away are altering this remote place, and that if the warming/melting cycle continues, we'll feel the influence of the Arctic. Droughts and floods will increase, water supplies will diminish as glaciers and snow cover decline, and coasts will erode as sea level rises. Nobody knows precisely how fast permafrost will melt or how quickly it will let loose the carbon it holds. It could happen over hundreds of years, or thousands.
There's no easy fix for slowing the release of carbon from permafrost. We can't put a lid over the tundra or tinker our way out of the problem. It's a cycle we can't control. Where we can make a difference, says Bret-Harte, is at home. "In theory we can make a treaty to say let's not burn fossil fuels anymore. We can't make a treaty to stop thermokarsts and fires."
This story was titled "Smoke Signals" in Audubon's May-June 2010 issue.