The World in 2050_ Four Forces Shaping Civilization's Northern Future - Laurence C. Smith [164]
379 This map is assembled from several types of data. The permafrost load-bearing capacity model (gray tones) is very new and will comprise the Ph.D. dissertation of D. Streletskiy, University of Delaware. Permafrost is warmed by rising air temperatures and/or deeper winter snowpack (deeper snow insulates the ground). In general, warmer permafrost means lower load-bearing capacity, but other factors like geology, ice content, and thermal properties are also important. These processes have recently been incorporated into Streletskiy’s semiempirical model, driven here by NCAR CCSM3 projections of surface temperature and snow depth averaged over fifteen-year periods, 2000-2014 and 2045-2059, assuming an SRES A1B emissions scenario. The map shows the projected changes occurring between those two time intervals. “Severe loss” is strength loss of >50%, “moderate” is 25-50%, and “mild” is under 25%. The hatched markings refer to increased travel cost from reduced winter road suitability, work done at UCLA by my graduate student Scott Stephenson. Winter roads may only be used for transport where climate provides suitable conditions for their construction and use. Winter road suitability is strongly correlated with freezing index, which is a function of temperature. Land area was classified as suitable for winter road use where mean temperature was 0°C or lower and snow depth exceeded 20 cm. Rivers and lakes were classified as suitable if they received at least 23 cm of freeze depth. Suitability losses were cumulated from November to March. Again, NCAR CCSM3 projections of surface temperature were averaged over fifteen-year periods 2000-2014 and 2045-2059 assuming a SRES A1B emissions scenario, with the map showing the projected change in areal extent of suitability occurring between those two time intervals. Note that this map does not require that winter roads are currently being used in these areas, but instead measures the climatic suitability for their potential use.
380 Personal interview with D. Augur, assistant deputy minister, NWT Department of Transportation, Yellowknife, July 9, 2007. On average, permanent roads cost $0.5-$1.0 M/km to build, whereas winter roads average $1,300 M/km.
381 The Tibbitt-Contwoyto is jammed with heavy trucks during its brief operating season. In 2007 it absorbed eleven thousand loaded trips in just seventy-two days. D. Hayley and S. Proskin, “Managing the Safety of Ice Covers Used for Transportation in an Environment of Climate Warming,” 4th Canadian Conference on Geohazards, May 20-24, 2008, Québec City, Canada.
382 Geologically speaking, a kimberlite pipe. Diamonds form under extreme pressure deep in the Earth’s crust but can sometimes be found in kimberlite pipes, narrow chimneys of igneous rock that can reach the surface. In the NWT kimberlites are often found under lakes because they are softer than the surrounding granitic rocks, thus becoming eroded depressions that fill with water.
383 Personal interview with Tom Hoefer, manager of external and internal affairs, Diavik Diamond Mines, Inc., Yellowknife, NWT, July 9, 2007.
384 Personal interview with Divisional Forester Jeremy Beal, Tolko Industries Ltd., High Level, Alberta, June 4, 2007.
385 Compared with other types of road, properly constructed and used winter roads have surprisingly low impact on the environment, especially over lakes and wetlands. See S. Guyer, B. Keating, “The Impact of Ice Roads and Ice Pads on Tundra Ecosystems,” National Petroleum Reserve-Alaska, U.S. Bureau of Land Management, BLM-Alaska Open File Report 98 (April 2005), 57 pp.
386 L. D. Hinzman et al., “Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions,” Climatic Change 72 (2005): 251-298.
387 One of the ways to mitigate the climate-warming effect is to deploy sweepers