In southern Alaska, the permafrost has gone from 0 days per year above freezing in 1987 to 139 days above freezing in 1993.
Permafrost, or permanently frozen ground, is soil, sediment, or rock that remains at or below 0°C for at least two years. It occurs both on land and beneath offshore Arctic continental shelves, and its thickness ranges from less than 1 meter to greater than 1,000 meters.
permafrost and the resulting microbial decomposition of
previously frozen organic carbon (C) is one of the most significant
potential feedbacks from terrestrial ecosystems to the
atmosphere in a changing climate... Accounting for C stored
deep in the permafrost more than doubles previous high-latitude
inventory estimates, with this new estimate equivalent to twice
the atmospheric C pool. The thawing of permafrost with warming
occurs both gradually and catastrophically, exposing organic C to
microbial decomposition. Other aspects of ecosystem dynamics
can be altered by climate change along with thawing permafrost,
such as growing season length, plant growth rates and species
composition, and ecosystem energy exchange. However, these
processes do not appear to be able to
compensate for C release from thawing permafrost, making it likely that the net effect of widespread permafrost thawing will be a positive feedback to a warming climate." -- Schuur et. al, 2008
Thawing Permafrost in Alaska
A thaw in the permafrost is a very bad thing for global warming, for when the permafrost thaws, decay of its rich peat can begin, releasing massive quantities of carbon dioxide if the decay occurs aerobically, and massive quantities of methane if the decay occurs under water.
The National Snow and Ice Data Center has collected daily soil temperatures at various depths from 1986 until funding ended in 2003 at sites in Alaska. Sites were chosen to represent different permafrost regions, for their length of record, and ongoing availability of the data. They sought to avoid sites with undue human influence, such as oil field construction. The data were obtained by remote, battery-powered, computer-controlled automatic temperature loggers. Temperatures recorded were usually in the air, at the ground surface, in the active layer, at the permafrost table, and in the permafrost.
Hogan Hil Temperature Changes
The file HH01.txt contains Air, and ground temperature
measurements for 3,618 days of observations stretching from
October 1986 through September 1996 for Hogan Hill. The
graph below shows the annual ocillations in air temperature.
We computed number of days when the temperature was above freezing for each year in which temperatures were recorded on every day. The graph below shows these results for air temperature and for the permafrost measured at a depth of 0.69 meters. A best fit line makes it easier to see the increased number of days in which the permafrost at this depth was above freezing.
Barry, R., T. Zhang, and D. Gilichinsky, compilers.2001. Russian historical soil temperature data.Boulder, CO : National Snow and Ice Data Center.Digital media.
Brown, J., O.J. Ferrians, Jr., J.A. Heginbottom, and E.S. Melnikov. 1998. Digital Circum-Arctic Map of Permafrost and Ground-Ice Conditions. In International Permafrost Association, Data and Information Working Group, comp. Circumpolar Active-Layer Permafrost System (CAPS) version 1.0. Available from NSIDC User Services.
ENN News Archive. 1999. Warm Arctic may enhance global warming. 1 March 1999. Environmental News Network.
Goulden, M.L., S.C. Wofsy, J.W. Harden, S.E. Trumbore, P.M. Crill, S.T. Gower, T. Fries, B.C. Daube, S.-M. Fan, D.J. Sutton, A. Bazzaz, and J. W. Munger. 1998. Sensitivity of boreal forest carbon balance to soil thaw. Science 279: 214-217.
Isaksen, Ketil, R.E. Benestad, C. Harris, and J.L. Sollid. 2007. Recent extreme near-surface permafrost temperatures on Svalbard in relation to future climate scenarios. Geophysical Research Letters doi:10.1029/2007GL031002.
Isaksen, Ketil and Johan Ludvig Sollid The permafrost on Svalbard and in Norway is thawing. Center for International Cliamte and Environmental Research, Oslo. http://www.cicero.uio.no/fulltext/index_e.aspx?id=2059
Lawrence, D.M., and A.G. Slater. 2005. A projection of severe near-surface permafrost degradation during the 21st century. Geophysical Research Letters doi:10.1029/2005GL025080.
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Nelson, F.E., O.A. Anisimov,
and N.I. Shiklomanov. 2001. Subsidence risk from thawing
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Osterkamp, T.E. 2007. Characteristics of the recent warming of permafrost in Alaska. Journal of Geophysical Research doi:10.1029/2006JF000578.
Schuur, Edward A. G., James Bockheim, Josep G. Canadell, Eugenie Euskirchen, Christopher B. Field, Sergey V. Goryachkin, Stefan Hagemann, Peter Kuhry, Peter M. Lafleur, Hanna Lee, Galina Mazhitova, Frederick E. Nelson, Annette Rinke, Vladimir E. Romanovsky, Nikolay Shiklomanov, Charles Tarnocai, Sergey Venevsky, Jason G. Vogel, and Sergei A. Zimov. Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle. BioScience • September 2008 / Vol. 58 No. 8. http://www.aibs.org/bioscience-press-releases/resourc es/Schuur.pdf
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Zhang, T., R.L. Armstrong, and J. Smith. 2003. Investigation of the near-surface soil freeze-thaw cycle in the contiguous United States: algorithm development and validation. Journal of Geophysical Research doi:10.1029/2003JD003530.
Zhang, T., R.G. Barry, K. Knowles, J.A. Heginbottom, and J. Brown. 1999. Statistics and characteristics of permafrost and ground ice distribution in the Northern Hemisphere. Polar Geography 23(2): 147-169.
Zhang, T., R.G. Barry, K. Knowles, F. Ling, and R.L. Armstrong. 2003. Distribution of seasonally and perennially frozen ground in the Northern Hemisphere. In Permafrost. Phillips, Springman, and Arenson, eds. Swets and Zeitlinger.
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Gilichinsky, compilers. 2001, updated 2006. Russian historical
soil temperature data. Boulder, Colorado USA: National Snow
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Other Papers in this Series
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- Thawing Permafrost In southern Alaska, the permafrost has gone from 0 days per year above freezing in 1987 to 139 days above freezing in 1993. Last revised Wednesday, January 14, 2009.
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- Trends in Snow and Ice Cover In the Northern Hemisphere, the average snow extent has decreased by 3.75 million square Km in the last 39 years. The greatest loss of snow cover has occurred in the months of June and July. In the Northern Hemisphere, the average extent of sea ice decreased by 1.5 million square Km during the period 1978-2008, from about 9.9 million square Km to about 8.4. In the Southern Hemisphere in this period, the extent of sea ice did not change significantly. Reduced snow and ice cover changes albedo, increasing the rate of warming. Last revised Friday, January 16, 2009.
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© 2009 David Stang. All rights reserved.
Dr. Stang is available for presentations on this topic. Contact him by email.
Last Revised: Wednesday, January 14, 2009