Scientists are announcing a surprising find from the arctic: new permafrost is still forming. But it is unlikely to survive beyond the end of the century. That’s according to a new study out this week in the publication Geophysical Research Letters. Researchers made the discovery at a lake in Alaska’s Eastern Interior.
(Credit Martin Briggs / US Geological Survey)
Twelvemile Lake, southwest of Fort Yukon is disappearing. Over the last three decades, scientists say the lake has lost 15 feet of water.
“Across the arctic, there’s a lot of lakes that we know are getting smaller,” says Jeffrey McKenzie, a professor at McGill University in Montreal. He and fellow researchers thought that water was draining from the lake bottom. “So, if you were top image all the permafrost the Yukon flats, it almost looks like Swiss cheese and there’s a bunch of holes in the permafrost where the lakes are.”
Those ‘holes’ are called taliks. In the summer of 2011 and 2012, McKenzie joined scientists from the US Geological Survey to find out why Twelvemile Lake was shrinking.
“The initial part of the study was to think about somehow water from Twelvemile Lake was going downward through this talik, or this hole in the permafrost and somehow joining the regional groundwater system and then somewhere else, likely the Yukon River,” he said.
The team conducted surveys, probed the ground and used computer models. What they found was that despite a decrease in the water level, it wasn’t necessarily draining from the lake.
“You have this new shoreline that’s continually emerging,” says McKenzie. “Where this new shoreline is emerging, you’re getting new plants, new grasses, new ecology forming in these areas, and the particular part that’s really interesting, is that where willow shrubs started to grow in this new land, below the willow shrubs, permafrost started to form.”
McKenzie says there are a number of factors that contribute to this permafrost ‘aggradation.’
“The willow shrubs are shading the land surface, so during the summer, there’s less incoming solar radiation warming up the ground in these places. Additionally, the willows extract a lot of water from the ground so there’s less surface recharge and less snowmelt going into the ground. There’s also some thermodynamic effects as the willows actually extract the water from the ground, it helps cool the ground potentially.”
In general, permafrost can last for hundreds, even thousands of years, but McKenzie says the new stuff forming at Twelvemile Lake, and potentially elsewhere across the arctic is unlikely to last beyond the end of the century.
“An unfortunate element would be that with ongoing climate change the temperature will continue to rise, especially in central Alaska,” McKenzie explains. “They think over the next 100 or 90 years, the temperature is estimated to rise by at least three degrees Celsius and with this rise in temperature, it basically will wipe out any new permafrost that will form.”
McKenzie says in some locations on the Yukon Flats, bands of young willows could indicate the formation of new permafrost. Researchers plan to expand their study beyond Twelvemile Lake. Funding for the study comes from the US Department of Defense Strategic Environmental Research and Development Program and the USGS.
