Permafrost, or permanently frozen ground, is soil, sediment, or rock that remains at or below 0°C for at least two years. North of the Brooks Range, permafrost occurs as a continuous sheet extending from a few inches below the surface down as much as 1000 feet1. Although permafrost may occur in any region where the average annual temperature is freezing or below, it gets progressively thinner and discontinuous in extent until nearly entirely absent in Southeast Alaska and along the Aleutian Islands. Permafrost physically supports the ground surface, controls soil temperature and moisture, modifies microtopography, controls subsurface hydrology and rooting zones, and influences nutrient cycling. Borehole measurements taken along a north-south transect of Alaska document permafrost warming throughout most of the region. Total warming at the permafrost surface between 1977 through 2003 was 3 to 4 °C for the Arctic Coastal Plain, 1 to 2 °C for the Brooks Range including its northern and southern foothills, and 0.3 to 1 °C south of the Yukon River8. Rising temperatures, degradation of permafrost, and loss of shore-fast ice along Alaska’s coasts exposes coastlines and coastal villages to increased coastal erosion and vulnerability to storm surges.
The thawing of ice-rich permafrost causes subsidence of the land surface, creating thermokarst ponds and causing trees to tilt, which is shown in this peatland terrain in Churchill, Manitoba.
The glacial mass balance record (the net gain or loss of ice over a year) has been negative for Alaska statewide since the mid-20th century, averaging approximately 11 km3/year from 1965 to 19939. Conditions for individual glaciers vary. While most Arctic glaciers have experienced predominantly negative balances over the past few decades, some may be positive where winter precipitation has increased9. The mountains around the Gulf of Alaska contain up to 90,000 km2 of glacier area including the largest glaciers outside of the polar regions. Longterm mass-balance time series for three relatively small glaciers in that region indicate that these glaciers follow a regional and global trend of accelerated melting since 198810. These changes also affect the seasonal discharge and turbidity of glacial streams13.
1Parson, E.A., L. Carter, P. Anderson, B. Wang, G. Weller. 1999. Potential Consequences of Climate Variability and Change for Alaska. U.S. Global Change Research Program. International Arctic Science Committee. Center for Global Change and Arctic System Research. Fairbanks, Ak. 30 pp. (pdf)
2Stafford, J.M., G. Wendler, and J. Curtis. 2000. Temperature and precipitation of Alaska: 50 year trend analysis. Theor. Appl. Climatol. Vol. 67: 33-44. (pdf)
4Klein, Eric. Berg, Edward. Dial, Roman. "Wetland drying and succession across the Kenai Peninsula Lowlands, South-Central Alaska." Canadian Journal of Forest Research (2005): pubs.nrc-cnrc.gc.ca/rp/rppdf/x05-129.pdf.
5IPCC. 2001. Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II, and III to the Third Assessment Report of the Integovernmental Panel on Climate Change [Watson, R.T. and the Core Writing Team (eds.)]. Cambridge University Press, Cambridge, United Kingdom, and New York, NY, USA, 398 pp. (pdf)
6Stroeve, J., M. M. Holland, W. Meier, T. Scambos, and M. Serreze (2007), Arctic sea ice decline: Faster than forecast? Geophysical Research Abstracts, Vol. 9, 01362. (pdf)
7National Snow and Ice Data Center Arctic Sea Ice News Fall 2007 web page accessed June 15, 2008. (pdf)
8Osternkamp, T.E. 2005. The recent warming of permafrost in Alaska. Global and Planetary Change. Vol. 49, Issue 3-4: pg. 187-202.
9Serreze, M.C., J. E. Walsh, F. S.Chapin III , T. Osterkamp, M. Dyurgerov, V. Romanovsky, W. C. Oechel, J. Morison, T. Zhang, and R. G. Barry. 2000. Observational evidence of recent change in the northern high-latitude environment. Climatic Change 46: 159–207.
10Meier, M.F. and M. B. Dyurgerov. 2002. How Alaska Affects the World. Science. Vol. 297:350-351.
11ACIA, 2005.Arctic Climate Impact Assessment. Cambridge University Press, 1042p. (pdf)
12Dyurgerov, M.B. and M.F. Meier. 2005. Glaciers and the changing earth system: A 2004 snapshot. Institute of Arctic and Alpine Research, University of Colorado. Occasional Paper No. 58. 188 pp.
13Kelly, B.P., T. Ainsworth, D.A. Boyce Jr., E. Hood, P. Murphy, and J. Powell. 2007. Climate Change: Predicted Impacts on Juneau. Report to City and Borough of Juneau. 86 pp. (pdf)