Study reveals lakes a major source of prehistoric methaneOctober 26, 2007
Methane bubbling from arctic lakes could have been responsible for up to 87 percent of that methane spike, said UAF researcher Katey Walter, lead author of a report printed in the Oct. 26 issue of Science magazine. The findings could help scientists understand how current warming might affect atmospheric levels of methane, a gas that is thought to contribute to climate change.
"It tells us that this isn't just something that is ongoing now. It would have been a positive feedback to climate warming then, as it is today," said Walter. "We estimate that as much as 10 times the amount of methane that is currently in the atmosphere will come out of these lakes as permafrost thaws in the future. The timing of this emission is uncertain, but likely we are talking about a time frame of hundreds to thousands of years, if climate warming continues as projected."
Ice cores from Greenland and Antarctica have shown that during the early Holocene Period--about 14,000 to 11,500 years ago--the levels of methane in the atmosphere rose significantly, Walter said. "They found that an unidentified northern source (of methane) appeared during that time."
Previous hypotheses suggested that the increase came from gas hydrates or wetlands. This study's findings indicate that methane bubbling from thermokarst lakes, which are formed when permafrost thaws rapidly, is likely a third and major source.
Walter's research focused on areas of Siberia and Alaska that, during the last ice age, were dry grasslands atop ice-rich permafrost. As the climate warmed, Walter said, that permafrost thawed, forming thermokarst lakes.
"Lakes really flared up on this icy permafrost landscape, emitting huge amounts of methane," she said.
As the permafrost around and under the lakes thaws, the organic material in it--dead plants and animals--can enter the lake bottom and become food for the bacteria that produce methane.
"All that carbon that had been locked up in the ground for thousands of years is converted to potent greenhouse gases: methane and carbon dioxide," Walter said. Walter's paper hypothesizes that methane from the lakes contributed 33 to 87 percent of the early Holocene methane increase.
To arrive at the hypothesis, Walter and her colleagues traveled to Siberia and northern Alaska to examine lakes that currently release methane. In addition, they gathered samples of permafrost and thawed them in the laboratory to study how much methane permafrost soil can produce immediately after thawing.
"We found that it produced a lot very quickly," she said.
Finally, she and other researchers studied when existing lakes and lakes in the past formed and found that their formation coincided with the early Holocene Period northern methane spike.
"We came up with a new hypothesis," she said. "Thermokarst lake formation is a source of atmospheric methane today, but it was even more important during early Holocene warming. This suggests that large releases from lakes may occur again in the future with global warming."
Co-authors on the paper include Mary Edwards of the University of Southampton and the UAF College of Natural Science and Mathematics; Guido Grosse, an International Polar Year postdoctoral fellow with the UAF Geophysical Institute; Sergey Zimov of the Russian Academy of Sciences; and Terry Chapin of the UAF Institute of Arctic Biology. Funding was provided by the National Science Foundation, the Environmental Protection Agency and the National Aeronautics and Space Administration.
University of Alaska Fairbanks
Related Methane Current Events and Methane News Articles
Deep-Earth Carbon Offers Clues About Origin of Life on Earth
New findings by a Johns Hopkins University-led team reveal long unknown details about carbon deep beneath the Earth's surface and suggest ways this subterranean carbon might have influenced the history of life on the planet.
Permafrost soil: Possible source of abrupt rise in greenhouse gases at end of last Ice Age
Scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have identified a possible source of carbon dioxide (CO2) and other greenhouse gases that were abruptly released to the atmosphere in large quantities around 14,600 years ago.
U-M students complete Detroit's first comprehensive greenhouse gas inventory
Energy use in buildings accounts for nearly two-thirds of the greenhouse gas emissions generated in Detroit, while exhaust from cars, trucks and buses is responsible for about 30 percent of the total, according to a new citywide inventory compiled by University of Michigan student researchers.
Future air quality could put plants and people at risk
By combining projections of climate change, emissions reductions and changes in land use across the USA, an international research team estimate that by 2050, cumulative exposure to ozone during the summer will be high enough to damage vegetation.
Climate change: Limiting short-lived pollutants cannot buy time on CO2 mitigation
Targeting emissions of non-CO2 gases and air pollutants with climate effects might produce smaller benefits for long-term climate change than previously estimated, according to a new integrated study of the potential of air pollution and carbon dioxide mitigation.
No quick fix for global warming
When fossil fuels are burned, other climate-forcing gases are produced in addition to long-lasting carbon dioxide.
Dartmouth study finds restoring wetlands can lessen soil sinkage, greenhouse gas emissions
Restoring wetlands can help reduce or reverse soil subsidence and reduce greenhouse gas emissions, according to research in California's Sacramento-San Joaquin River Delta by Dartmouth College researchers and their colleagues.
New study shows 3 abrupt pulse of CO2 during last deglaciation
A new study shows that the rise of atmospheric carbon dioxide that contributed to the end of the last ice age more than 10,000 years ago did not occur gradually, but was characterized by three "pulses" in which C02 rose abruptly.
NIST 'combs' the atmosphere to measure greenhouse gases
By remotely "combing" the atmosphere with a custom laser-based instrument, researchers from the National Institute of Standards and Technology (NIST), in collaboration with researchers from the National Oceanic and Atmospheric Administration (NOAA), have developed a new technique that can accurately measure-over a sizeable distance-amounts of several of the major "greenhouse" gases implicated in climate change.
Organic Molecules in Titan's Atmosphere Are Intriguingly Skewed
While studying the atmosphere on Saturn's moon Titan, scientists discovered intriguing zones of organic molecules unexpectedly shifted away from its north and south poles. These misaligned features seem to defy conventional thinking about Titan's windy atmosphere, which should quickly smear out such off-axis concentrations.
More Methane Current Events and Methane News Articles