Both methane and carbon dioxide are key greenhouse gases. They absorb long-wave radiation and trap heat in the Earth’s lower atmosphere. The research team says this makes northern Russian a major player in future global warming scenarios.
“The study shows the potential role of Siberian peatlands as a major piece of the greenhouse gas puzzle, both in the past and the future,” said Glen MacDonald, chair of geography department at the University of California, Los Angeles (UCLA), and co-author of the study published today in the research journal Science.
UCLA researcher Laurence Smith led a 22-member international team to the West Siberian Lowland. The region—a flat, mosquito-infested plain of wetlands, tundra, and scattered larch forests—covers half a million square miles (1.3 million square kilometers), the largest expanse of peatlands in the world.
“If you pushed all the individual peat bogs together they themselves would cover at least 233,000 square miles [603,445 square kilometers], almost as big as Texas,” Smith said.
Radiocarbon Dating
Radiocarbon dating revealed that the bogs were 2,000 to 3,000 years older than previously thought, and researchers believe the bogs may be responsible for a huge rise in atmospheric methane levels (identified from Arctic ice core records) 9,000 to 11,500 years ago.
Previous explanations for this rise in methane gas included catastrophic releases from the seafloor and emissions from tropical rain forests. “Now we [also] suspect these peatlands,” said Smith.
Peat forms in cool, wet regions, especially at northern latitudes, where dead plant material doesn’t fully decompose. Over time, peat builds up in layers thousands of years old. Where the ground is particularly soggy and oxygen-poor, anaerobic bacteria attempts to digest organic matter, producing methane gas and a noxious odor.
Smith says the methane spurt during the early Holocene period is probably best attributed to a combination of factors, including warming temperatures and closer plant contact during the early stages of peat formation with the nutrient-rich, mineral substrate.
Core samples of the peat, which reaches depths of 33 feet (10 meters), revealed that different species typical of low wetland areas dominated at the time. The study team calculates these plants would have produced about six times more methane than today’s bog-dwelling plants such as sphagnum moss.