Thursday, July 03, 2008
Permafrost Not So Permanent
While we are waiting to see the extent of this years Arctic Ocean ice melt the the National Snow and Ice Data Center has disturbing news regarding the so-called permafrost of the Arctic: it's melting also:
"The rate of climate warming over northern Alaska, Canada, and Russia could more than triple during extended episodes of rapid sea ice loss, according to a new study from the National Center for Atmospheric Research (NCAR) and the National Snow and Ice Data Center (NSIDC). The findings raise concerns about the thawing of permafrost, or permanently frozen soil, and the potential consequences for sensitive ecosystems, human infrastructure, and the release of additional greenhouse gases.
“The rapid loss of sea ice can trigger widespread changes that would be felt across the region,” said Andrew Slater, NSIDC research scientist and a co-author on the study, which was led by David Lawrence of NCAR. The findings will be published Friday in Geophysical Research Letters.
Last summer, Arctic sea ice extent shrank to a record low. From August to October last year, air temperatures over land in the western Arctic were also unusually warm, reaching more than 4 degrees Fahrenheit (2 degrees Celsius) above the 1978-2006 average. This led the researchers to question whether the unusually low sea ice extent and warm land temperatures were related.
Lawrence, Slater, and colleagues used a climate model to explore the relationship between low sea ice extent, increased air temperatures, and permafrost thawing. Previous climate change simulations identified periods of rapid sea ice loss that last 5 to 10 years. The new study shows that during such episodes, Arctic land would warm 3.5 times faster than average rates of warming predicted by global climate models for the 21st century.
The findings point to a link between rapid sea ice loss and enhanced rate of climate warming, which could penetrate as far as 900 miles inland. In areas where permafrost is already at risk, such as central Alaska, the study suggests that periods of abrupt sea ice loss can lead to rapid soil thaw.
Thawing permafrost may have a range of impacts, including buckled highways and destabilized houses, as well as changes to the delicate balance of life in the Arctic. In addition, scientists estimate that Arctic soils hold at least 30 percent of all the carbon stored in soils worldwide. While scientists are uncertain what will happen if this permafrost thaws, it has the potential to contribute substantial amounts of greenhouse gases to the atmosphere.
Funding for the research came from the National Science Foundation and the U.S. Department of Energy.
To read the full NCAR press release, visit the NCAR News Center at http://www.ucar.edu/news/."
In addition to the obvious other implications of permafrost melt include accelerated release of greenhouse gases especially methane which is far more potent than CO2. As per Kuuvik River:
"The trends for methane emissions from “not-so-perma” permafrost terrain in the Northern Hemisphere are ominous. In Siberia, a region with colossal stores of partially decomposed organic matter sealed below frozen substrate, methane flux to the atmosphere was recently documented to be occurring five times faster than estimated before. Accordingly, Russian and American scientists have calculated that methane emissions for the region have increased at least 58% since 1974. Moreover, radiocarbon dating of methane emitted from the Siberian research sites indicates that at least 40% of the methane emitted at those locations is from vegetatation that lived and froze 35,260–42,900 years ago; thus vegetation frozen since the Pleistocene epoch is now decomposing and emitting methane.
During the Pleistocene epoch most of the northern Siberian plains were unglaciated and accumulated vast volumes of organic carbon in sediments. Hence in just one part of Siberia, for instance, an area known as the Yedoma Ice Complex, the Siberian landscape is currently storing about 500Gt of near-surface carbon. This high-latitude carbon sink is vulnerable and could greatly intensify global warming via greenhouse gas emissions if northeast Siberia continues to warm in the future, as computer climate models suggest it will. Not counting future greenhouse gas emissions from everywhere else in the world, the Yedoma Ice Complex alone has the potential to release an amount of methane that is about ten times the amount now in Earth’s atmosphere. According to the Earth System scientists who have verified the accelerating Siberian emissions “the large pool of still-frozen Pleistocene-age C in Siberia is a methane time bomb” -- a time bomb ticking to emit about 100 times the amount of carbon that humans currently pollute each year via burning fossil fuels.
Permafrost is a temperature sensitive indicator of millennial climatic variability -- that fact is increasingly obvious to more and more people. With Arctic temperatures now warming and snow and ice decreasing, permafrost is melting. Which raises the logical question: how much permafrost will melt worldwide, and how soon will it happen? An American climate model run answered this question in 2005, and calculated that up to 90% of all Northern Hemisphere permafrost will melt before the year 2100. The very serious implications of this model result, incidentally, would only be further accentuated if such a climate model were to factor-in the since discovered accelerating methane flux emanating from the Yedoma Ice Complex. Simple lesson then -- we humans, via our naive meddling with the chemistry of the atmosphere that keeps us alive, have sparked unusual biogeochemical fluxes in our Earth System that are serious and seemingly irreversible."