New analyses of stored carbon in permafrost presented at last week’s annual American Geophysical Union (AGU) meeting are causing greater concern amongst climate scientists.
One of the new analyses (Hugelius et al) of soil carbon in permafrost utilized data from both new field work and archival records, totaling over 400 sites. The analysis estimates that 1.9 trillion tons of carbon lay stored in the Northern hemisphere’s frozen soil, up to 3 meters in depth.
(Note: due to logistical constraints, and prevailing assumptions, earlier sampling of sites was limited to just the top meter of permafrost. More recently, many scientists have begun thinking that carbon trapped further down — to a depth of 3 meters — is also vulnerable to thawing and release.)
An influential 2009 study estimated this total to be 1.6 trillion metric tons but was based upon samplings of just 45 sites (at that depth).
This newest figure is more than 15% greater than the previous, highest estimates, indicating that climatologists have underestimated the impact on the climate if this carbon were to be ‘liberated’.
“What happens in the Arctic doesn’t stay in the Arctic.” – Peter Griffith, ecosystems ecologist, NASA’s Goddard Space Flight Center, Greenbelt, Maryland
Permafrost, or cryotic soil, is soil that is below the freezing point of water for 2 or more years. It spans a quarter of the Northern Hemisphere landmass — from Alaska to Canada and from Northern Scandinavia and across Siberia.
As permafrost thaws, decomposing, carbon-hungry microbes convert much of the carbon into carbon dioxide which enters the atmosphere and serves as a driver of global warming. This ‘climate forcing’ effect amplifies warming impacts and could possibly push the climate into a dangerous positive feedback loop,
Frozen soil and permafrost can contain many different materials (e.g., bedrock, sediment, detritus) including water and ice. But not all frozen ground and permafrost contains ice, or large amounts of it. Thus permafrost tends to thaw rather than melt, just as leaving the freezer door open may cause the ice to melt, but only cause thawing of the food solids.
Thawing of this frozen soil has become a growing concern for climate scientists over the past several years, but the biggest problem has been accurately estimating the total amount of carbon stored in it. These newt analyses are sounding a few alarms.
More Analysis, Another Troubling Estimate
In another analysis of 9 earlier studies, presented at the AGU meeting by soil biogeochemist Christina Schaedel (University of Florida, Gainesville), the results showed that thawed permafrost could release 20% of its stored carbon over the next 50 years. Schaedel calls this “a conservative estimate.”
According to the researchers, this amount could produce a carbon “pulse” greater than that from 2 year’s worth of human industrial emissions. This is the ‘ticking carbon bomb’ alluded to in the title.
The tricky part to any such analysis is accurately estimating how much permafrost will thaw (and thus how much of the stored carbon will be liberated) from a given amount of warming. One earlier permafrost modeling study estimated that, at current GHG emission rates, some 436 gigatons of carbon could enter the atmosphere by the end of the century.
The Current State of Things
It is crucial that environmental policy makers have accurate data and estimates to buttress their recommendations to government agencies (e,g., for mandatory, target reductions CO2)
Thawing permafrost, and the consequent release of large quantities of CO2, can accelerate the impacts from (industrial) greenhouse gas emissions.
Citing potential outcomes (from this acceleration) such as increased sea level rise, more intense droughts, and greater ocean acidification, Peter Griffith, an ecosystems ecologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, stated in a press statement: “The actual situation is worse” than policymakers realize,
Both Hugelius and Schaedel are part of a network of scientists studying the Arctic’s permafrost. Griffith is heading a new, decade-long NASA project to collect more soil carbon and ice data, of which there is currently a great lack.
Some source material (and quotes) for this article came from the Science News article: ‘Ticking Arctic Carbon Bomb May Be Bigger Than Thought’ by Eli Kintisch
Second Photo: (digging in permafrost); Nick Bonzey ; CC -By – SA 2.0
Chart:(types of permafrost) National Snow and Ice Data Center/World Data Center for Glaciology