About the Two Greenhouse Gases
The cold and wet soils of the Arctic do not decompose organic matter as fast as those in the temperate and tropical climate zones. They accumulate carbon faster than they release it. Scientists say if the Arctic gets warmer and drier, the stored carbon will be released mostly in the form of carbon dioxide gas. If the Arctic gets warmer and wetter, the stored carbon will be released mostly in the form of methane gas. On a 100 yr time scale, scientists say methane is 22x more potent than carbon dioxide as a greenhouse gas. On a shorter 20 yr time scale, it is 105x more potent. It has a high Global Warming Potential on a shorter time scale because it decays into water and carbon dioxide in about 12 yrs. Its effects are lasting, but most pronounced in the short term. If only 1% of the gases released over a short term is methane, the impact is as if 99% was carbon dioxide. A major goal of CARVE is to measure the ratio of methane to carbon dioxide being released today. This will allow for more accurate prediction tomorrow.
Flights of the C-23 Sherpa Aircraft
The CARVE mission is now in its third year. The team flew test flights in 2011. Science flights were conducted in 2012. Teams are working on the 2013 flights. April and May are finished. June flights are underway. Seven flight are planned for this year.
The two-week flights across the Alaskan Arctic are looking for seasonal variations in the carbon cycle. Thawing is in April-May. The summer growing season is in June-July. Everything refreezes and snow returns in September-October. Flights are from a base in Fairbanks. The C-23 flies about eight hours a day to sites on Alaska's North Slope, interior and Yukon River Valley. They cover tundra, permafrost, boreal forests, peatlands and wetlands. Below are three flight records from 2012. Reds and yellows show high concentrations of methane, and blues low.
The C-23 is not a very modern or stylish plane. It has a lot of utility for this mission. One person refers to it as "a UPS truck with a bad nose job." Everyone must wear noise cancellation headphones. "When you take them off, the sound is like being at a NASCAR race."
The plane gives the science teams low altitude and broad coverage access for the air sampling requirements. Most flights are at 500 ft (152 m). There are periodic ascents to higher elevations that give a check on the normal background levels of CO2 and methane. They sample the air with several instruments. One is a simulator for the Orbiting Carbon Observatory to be launched in 2014. Navigation data and scientific data are both collected and given to scientists within 12 hours of a flight.
Early Results from CARVE
The first year of science flights in 2012 are yielding results that are getting the attention of researchers.
"Some of the methane and carbon dioxide concentrations we've measured have been large, and we're seeing very different patterns from what models suggest," Miller said. "We saw large, regional-scale episodic bursts of higher-than-normal carbon dioxide and methane in interior Alaska and across the North Slope during the spring thaw, and they lasted until after the fall refreeze. To cite another example, in July 2012 we saw methane levels over swamps in the Innoko Wilderness that were 650 parts per billion higher than normal background levels. That's similar to what you might find in a large city."
Research is still ongoing. No one knows yet if a permafrost tipping point has been reached, or is near in the future. This CARVE mission is one way the researchers hope to find the answer and the specific triggers that cause it.
Other institutions participating in CARVE include City College of New York; the joint University of Colorado/National Oceanic and Atmospheric Administration's Cooperative Institute for Research in Environmental Sciences, Boulder, Colo.; San Diego State University; University of California, Irvine; California Institute of Technology, Pasadena; Harvard University, Cambridge, Mass.; University of California, Berkeley; Lawrence Berkeley National Laboratory, Berkeley, Calif.; University of California, Santa Barbara; NOAA's Earth System Research Laboratory, Boulder, Colo.; and University of Melbourne, Victoria, Australia.