YELLOWSTONE NATIONAL PARK, Wyo. -- Hot springs and other thermal features at Yellowstone National Park vent millions of tons of the greenhouse gas carbon dioxide each year, more than a typical industrial power plant, researchers from Pennsylvania State University have found.
Industrial smokestacks are normally seen as the prime suspects for the increase of carbon dioxide levels, but hot spring systems like Yellowstone's produce enough carbon dioxide that they, too, should be considered when the world tallies its carbon dioxide emissions, the researchers said.
Cindy Werner, a geoscience graduate student at Penn State, spent much of last summer sampling gases emerging from thermal vents, mud pots and adjacent ground in Yellowstone's Mud Volcano area. Much of the carbon dioxide appeared to escape along fault lines running through the area.
Ms. Werner and Prof. Susan Brantley of Penn State calculate that Yellowstone's thermal regions annually vent millions of tons of carbon dioxide.
They presented their results last week in a special session on Yellowstone at the annual meeting of the American Geophysical Union in San Francisco.
Ms. Werner and her colleagues found that Yellowstone's Mud Volcano area produced about 176,300 tons of carbon dioxide each year.
Loosely expanding those figures based on the park's underlying geology, they suggest that each year the entire park may emit about 44 million tons of carbon dioxide, a colorless, odorless and incombustible gas.
By contrast, a medium-sized power plant that burns fossil fuels is estimated to release 4.4 million tons of carbon dioxide into the atmosphere each year.
"We believe that geothermal systems are significant contributors to global estimates" of carbon dioxide, Ms. Werner said.
Carbon dioxide levels in Earth's atmosphere have increased to more than 350 parts per million today from 290 parts per million in 1890. Most of the blame for the increase has focused on the burning of fossil fuels and a widespread loss of tropical forests that, when healthy, recycle the gas into oxygen.
Many scientists believe that global temperatures will rise because increasing levels of carbon dioxide will trap and retain heat from the Sun in a process similar to what happens in a greenhouse. Such a warming trend could lead to rising sea levels, cause severe drought and storms and severely disrupt Earth's biological systems.
Scientists have long known that volcanic systems like the one that drives Yellowstone emit large amounts of carbon dioxide along with their heat. But there have been few efforts to measure the gas emissions of geothermal systems not associated with volcanoes that have erupted in modern times.
The Penn State scientists focused on the Mud Volcano area because its features are primarily gas-driven. They do not produce the prodigious amounts of water that flow from the park's main hot-spring basins.
Gases emerging from vents in the area also include high levels of helium-3, a helium isotope present in Earth's mantle but not its atmosphere.
The helium-3 at Mud Volcano suggests that the heat that keeps the area simmering has taken a relatively direct course from the mantle to the surface.
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