Key Facts

The city of Nome, on Alaska's Seward Peninsula, is mostly underlain by permafrost (permanently frozen ground). The region is home to many thaw ponds—composed of water from melting permafrost. Rising temperatures linked to global warming are shrinking these ponds, which may be releasing heat-trapping gases stored underneath.

• Alaska is warming at around twice the rate of the rest of the United States. The average annual air temperature has risen 6.1° F (3.4° C) in the past 50 years, while winters have warmed by 11.3° F (6.3° C).^2,3 The Nome area saw a warming trend from 1907 to 1941, and again from 1976 through early this century.⁴
• Permafrost temperatures in the state have increased since the late 1970s, and in regions where permafrost tends to be thinner—such as on the Seward Peninsula—it is more susceptible to thawing.^{2,3,4,5,6,7,8}
• Permafrost degradation is projected to increase the cost of maintaining public infrastructure in Alaska by 10-20 percent (U.S. $4 billion to $6 billion) by 2030, and another 10-12 percent ($5.6 billion to $7.6 billion) by 2080.⁹

Details

The Seward Peninsula—just below the Arctic Circle, and bordering both the Chukchi and Bering seas—is about 210 miles (330 kilometers) long, and 90-140 miles (145-225 kilometers) wide.^10,11 The peninsula was once part of the Bering land bridge—a thousand-mile swath of land that connected Siberia with Alaska during the last Ice Age when sea level was lower.^10,11 A majority of the land on the Seward Peninsula—composed mostly of vast, roadless tundra bisected by mountains and rivers—is public, and managed by various federal and state agencies.¹² Regional native corporations usually own any land that is not public.¹²

Nome, home to about 3,400 residents in 2009, sits on the southern side of the Seward Peninsula.¹³ The Nome area saw a warming trend from 1907 to 1941, and again from 1976 through early this century.⁴ As might be expected given these trends, and like much of the rest of Alaska, Nome is undergoing physical changes linked to global warming.^8,14

Permafrost, an essential component of many high-latitude landscapes, is present in about 85 percent of Alaska.^15,16 In Arctic regions, permafrost temperatures often sink to 17.6° F (-8° C) or lower.¹⁵ The permafrost layer averages 656 feet (200 meters) thick, but can grow to 2,132 feet (650 meters) thick.¹⁵ However, because Nome has a subarctic climate, the permafrost in and around the city tends to be much thinner: 49-164 feet (15-50 meters) thick.^4,7

Since the late 1970s, permafrost temperatures across the state—including on the Seward Peninsula—have risen along with increasing air temperatures.^3,5 In fact, 22 of 24 thaw (thermokarst) ponds studied near Nome shrank over the latter half of the last century, with losses in surface area ranging from 6 to 100 percent, and averaging 55 percent.^4,8

By 2030, permafrost degradation is expected to raise the costs of maintaining public infrastructure by U.S. $3.6 billion to $6.1 billion, and by another $5.6 billion to $7.6 billion by 2080.^2,9 Those figures do not include damage to private infrastructure, such as houses, which analysts have yet to calculate.⁹

Part of a Larger Pattern

Permafrost is particularly sensitive to increases in air temperature and changes in snow cover, making it especially vulnerable to climate change.^17,18 And permafrost degradation, in turn, is likely to amplify warming linked to climate change by releasing more heat-trapping gases stored in soil—often for thousands of years—to the atmosphere.

Permafrost can release both carbon dioxide and methane as it thaws, depending on moisture conditions and whether the permafrost has contact with air.^17,19 Scientists think that permafrost degradation causes a thickening of the top active layer—which thaws in the summer and freezes in the winter—enhancing the release of methane and carbon dioxide.^17,18

Thawing permafrost is also expected to alter area landscapes and make local ecosystems more susceptible to long-term damage, in part because permafrost degradation can lead to significant changes in local soil temperatures and moisture levels.^14,20,21 Soils on or near the banks of thermokarst ponds tend to be much drier than those on level tundra, owing to higher soil temperatures and drainage.^14,20,21 On the Seward Peninsula, the banks of these ponds host trees (usually spruces) and shrubs that are otherwise usually absent in the characteristically treeless tundra.^14,21

The continued shrinkage of thaw ponds could bring significant changes to local ecosystems, as spruce forest is likely to supplant tundra as the dominant land cover.^14,20 This could lead to a northward advance of some species of plants and other trees, while leaving resident vegetation more vulnerable to early mortality—potentially further disrupting the climate.^14,20,21

What the Future Holds

In Alaska, average annual temperatures are projected to rise 3.5°-7° F (1.9°-3.9° C) by around 2050.² How much temperatures will rise in the second half of the century depends on whether we choose to continue releasing large amounts of heat-trapping emissions. Under such a scenario, temperatures in Alaska are expected to climb 8°-13° F (4.4°-5.8° C) by 2100.^2,22 If we curb our emissions, we can expect temperature increases of 5°-8° F (2.8-4.4°C).^2,22

The fate of Alaska's permafrost and thaw ponds depends on the choices we make today. Acting quickly to make deep cuts in our heat-trapping emissions can help protect permafrost against complete degradation.

Credits

Endnotes

1. Photograph used by permission. Patricia Oksoktaruk Lillie. Available online at http://www.flickr.com/ photos/ nome_lillies/ 270955433/ in/ gallery-49535267@N06-72157624638783386/, accessed March 9, 2011. ↑
2. U.S. Global Change Research Program. 2009. Global Climate Change Impacts in the United States. Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson, (eds.). Cambridge University Press, 2009. ↑
3. IPCC (Intergovernmental Panel on Climate Change). 2007. Summary for policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York: 1-18. ↑
4. Hinzman, L.D., N.D. Bettez, W.R. Bolton, F.S. Chapin, M.B. Dyurgerov, C.L. Fastie, B. Griffith, R.D. Hollister, A. Hope, H.P. Huntington, A.M. Jensen, G.J. Jia, T. Jorgenson, D.L. Kane, D.R. Klein, G. Kofinas, A.H. Lynch, A.H. Lloyd, A.D. McGuire, F.E. Nelson, W.C. Oechel, T.E. Osterkamp, C.H. Racine, V.E. Romanovsky, R.S. Stone, D.A. Stow, M. Sturm, C.E. Tweedie, G.L. Vourlitis, M.D. Walker, D.A. Walker, P.J. Webber, J.M. Welker, K.S. Winker, and K. Yoshikawa. 2005. Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions. Climatic Change, 72: pp. 251-298 ↑
5. Lettenmaier, D., D. Major, L. Poff, and S. Running. 2008. Water resources. In: The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States [Backlund, P., A. Janetos, D. Schimel, J. Hatfield, K. Boote, P. Fay, L. Hahn, C. Izaurralde, B.A. Kimball, T. Mader, J. Morgan, D. Ort, W. Polley, A. Thomson, D. Wolfe, M.G. Ryan, S.R. Archer, R. Birdsey, C. Dahm, L. Heath, J. Hicke, D. Hollinger, T. Huxman, G. Okin, R. Oren, J. Randerson, W. Schlesinger, D. Lettenmaier, D. Major, L. Poff, S. Running, L. Hansen, D. Inouye, B.P. Kelly, L. Meyerson, B. Peterson, and R. Shaw (eds.)]. Synthesis and Assessment Product 4.3. U.S. Department of Agriculture, Washington, DC: p. 121-150. ↑
6. U.S. Arctic Research Commission Permafrost Task Force. 2003. Climate Change, Permafrost, and Impacts on Civil Infrastructure. Report. Special Report 01-03. Online at www.arctic.gov/ publications/ permafrost.pdf. Accessed July 28, 2010 ↑
7. Yoshikawa, K. and L. Hinzman. 2003. Shrinking thermokarst ponds and groundwater dynamics in discontinuous permafrost', Permafrost Periglacial Process, 14: pp. 151-160. ↑
8. ACIA, 2005: Arctic Climate Impact Assessment: Cambridge University Press, New York. NY. Available at http://www.acia.uaf.edu/ pages/ scientific.html. Accessed July 25, 2010. ↑
9. Larsen, P.H., S. Goldsmith, O. Smith, M.L. Wilson, K. Strzepek, P. Chinowsky, and B. Saylor.2008. Estimating future costs for Alaska public infrastructure at risk from climate change. GlobalEnvironmental Change, 18: 442-457. ↑
10. Encyclopædia Britannica. 2010. Seward Peninsula. Online at http://www.britannica.com/ EBchecked/ topic/ 536909/ Seward-Peninsula. Accessed August 25, 2010. ↑
11. National Park Service. 2010. Bering Land Bridge National Preserve. Washington, DC. Online at http://www.nps.gov/ akso/ akarc/ cr_bela.htm. Accessed August 23, 2010. ↑
12. Reindeer Research Pogram, University of Alaska-Fairbanks. 2008.The Seward Peninsula. Available at http://reindeer.salrm.uaf.edu/ about_reindeer/ seward_peninsula.php. Accessed August 24, 2010. ↑
13. Alaska Community Database Community Information Services. 2010. Nome, AK. Available at http://www.commerce.state.ak.us/ dca/ commdb/ CIS.cfm. Accessed August 24, 2010. ↑
14. Lloyd, A.H., K. Yoshikawa, C.L. Fastie, L. Hinzman, and M. Fraver. 2003. Effects of permafrost degradation on woody vegetation at Arctic treeline on the Seward Peninsula, Alaska. Permafrost and Periglacial Processes 14:93-101. ↑
15. Jorgenson, M.T., C.H. Racine, J.C. Walters, and T.E. Osterkamp. 2001. Permafrost degradation and ecological changes associated with a warming climate in Central Alaska. Climatic Change 48:551-579. ↑
16. Osterkamp, T. E., D. C. Esch, and V. E. Romanovshy. 1998, Permafrost. In: Implications of global change in Alaska and the Bering Sea region, edited by G. Weller and P.S. Anderson. Fairbanks, AK: Center for Global Change and Arctic System Research, University of Alaska, pp. 115-127. ↑
17. Jorgenson, M.T., C.H. Racine, J.C. Walters, and T.E. Osterkamp. 2001. Permafrost degradation and ecological changes associated with a warming climate in Central Alaska. Climatic Change 48:551-579. ↑
18. Nelson, F.E., A.H. Lachenbruch, M.-K. Woo, E.A. Koster, T.E. Osterkamp, M.K. Gavrilova, and G. Cheng. 1993. Permafrost and changing climate. In: Proceedings of the sixth international conference on permafrost, vol. 2. Wushan, Guangzhou: South China University of Technology Press, pp. 987-1005. ↑
19. Lawrence, D.M., and A.G. Slater. 2005. A projection of severe near-surface permafrost degradation during the 21st century. Geophysical Research Letters 32:1-5. ↑
20. Lloyd, A.H., T. S. Rupp, C.L. Fastie, and A.M. Starfield. 2003. Patterns and dynamics of treeline advance on the Seward Peninsula, Alaska. Journal of Geophysical Research 108:1-15. ↑
21. Silapaswan, C.S., D.L. Verbyla, and A.D. McGuire. 2001. Land cover on the Seward Peninsula: The use of remote sensing to evaluate the potential influences of climate warming on historical vegetation dynamics. Canadian Journal of Remote Sensing 27:542-554. ↑
22. The emissions scenarios referred to here are the higher-emissions path known as A2 and the lower-emissions path known as B1 from the Intergovernmental Panel on Climate Change. ↑