Melting Permafrost | Links to Greenhouse Gases

Permafrost covers 24% of exposed land of the Northern Hemisphere.

From a NASA press release of 6-10-2013

Permafrost (perennially frozen) soils underlie much of the Arctic. Each summer, the top layers of these soils thaw. The thawed layer varies in depth from about 4 inches (10 cm) in the coldest tundra regions to several yards, or meters, in the southern boreal forests. This active soil layer at the surface provides the precarious foothold on which Arctic vegetation survives. The Arctic’s extremely cold, wet conditions prevent dead plants and animals from decomposing, so each year another layer gets added to the reservoirs of organic carbon sequestered just beneath the topsoil.

Over hundreds of millennia, Arctic permafrost soils have accumulated vast stores of organic carbon – an estimated 1,400 to 1,850 petagrams of it (a petagram is 2.2 trillion pounds, or 1 billion metric tons). That’s about half of all the estimated organic carbon stored in Earth’s soils. In comparison, about 350 petagrams of carbon have been emitted from all fossil-fuel combustion and human activities since 1850. Most of this carbon is located in thaw-vulnerable topsoils within 10 feet (3 meters) of the surface.

For an interactive book  about the frozen parts of Earth, follow this link to the publication.

Arctic air temperatures rose 1.5 – 2.5˚C in the past 30 yrs, faster than those of other regions of the globe. The permafrost layer temperatures have risen even faster at rates of 2.7 – 4.5˚C in 30 yrs. The released heat into the permafrost is likely to cause increased releases of carbon in the forms of CO2 and methane. The fear is this will alter the carbon balance of the Arctic and worsen global warming.

Scientists want to know how much of the carbon in permafrost is likely to be released and how fast. Current climate models do not account for this accurately. They need additional data to see how increased releases may affect larger regions and the globe as a whole. With this new data, the existing climate models can be modified and they may better predict the future behavior. To that end, teams from twelve institutions have joined NASA to fly low altitude missions in the Arctic. Their goal is to measure the exchanges of carbon taking place between Earth’s surface and atmosphere. The project is called CARVE – Carbon in Arctic Reservoirs Vulnerability Experiment.

Permafrost is not only in the exposed land areas. It is also common in the continental shelves of the Arctic Ocean as subsea permafrost. It was formed during the last glacial period. Sea levels were much lower then. These shelves endured very harsh conditions and accumulated large stores of organic undecayed carbon. Subsea permafrost is slowly thawing at many locations. Their extent and how they will impact global climate is lesser known.

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.

Institutions

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.

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