Ninth International Conference on Permafrost ... - IARC Research

Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tFigure 2. Soil temperature and water content for the 20 cm depth atDBM2 Ribdon met.Figure 3. Soil temperature profile for the 2007 summer at DBM2Ribdon met.DMB4, DMB5, and DMB6, respectively. Note that data arenot available at the regulated 30 cm depth, and so must beinterpolated by averaging data from the 20 and 40 cm depths.(See Figure 2 for an example of the 2006/2007 freeze/thawcurve at the 20 cm depth for DBM2 Ribdon met.) Relaxingtundra-travel regulations from -5°C to -2°C would addapproximately 34 days of travel time at station DBM2,approximately 28 days of travel time at station DBM4,approximately 30 days of travel time at station DBM5, andapproximately 29 days of travel time at station DBM6. Inall four cases, the majority of additional travel time wouldoccur during the winter freeze, as tundra soils freeze slowerthan they thaw. At each of the aforementioned sites, the ratioof additional winter travel time to additional summer traveltime was at least 1:1.4, with the mean ratio being 1:2.8, andthe maximum ratio being 1:4.9.Profile curves showing temperature changes based onsoil depth were also created for stations DBM2, DBM4,and DBM6. The dates selected on these plots correspond tospecific times when soil temperature at either the 20 or 40cm depth crossed a 1°C incremental threshold. (See Figure3 for an example of a temperature profile curve for DBM2Ribdon met for the 2007 summer period.) Of the analyzedstations, DBM2 had both the earliest freeze and earliest thawdates. In respect to DBM4 and DBM6, DBM2 is the furtheststation from the coastline. Soils at DBM4, the westernmoststation analyzed, began both the freeze cycle and thaw cycleon the latest dates.SummarySoil temperature data were collected and analyzed froma system of 12 weather stations. This data can be used tohelp evaluate tundra-travel management policy along theNorth Slope of Alaska. Variation in incremental one-degreeconditions in the freezing soils was used to illustrate thepotential differences in timing of tundra-travel openings.Relaxing tundra-travel regulations from -5°C to -2°Cwould add an average of 30 days of travel time throughoutthe analyzed stations, with the majority of additional timeoccurring during winter freeze-up. Freeze/thaw curves hadthe earlier start times at the inland locations, as compared tothose locations closer to the coastline.To better assess freeze/thaw tundra soil conditions, a largerquantity of data must be analyzed. Other station locationsas well as current winter freeze data should be plotted tobroaden the depth of analyzed trends. Spatial analyses ofdata will also be performed. Soil parameters associatedwith freeze/thaw cycles will be compared between coastaland foothill sites, as well as resulting variations from east/west locations. Current data for the 2007/2008 freeze curvewill also be compared to data from the previous winter. Soilstrengthmeasurements on a variety of soils as a functionof temperature and water content are also needed to betterrelate travel conditions to soil parameters.ReferencesBader, H.R. 2005. Tundra Travel Research Project: ValidationStudy and Management Recommendations. AlaskaDepartment of Natural Resources, 20 pp. http://www.dnr.state.ak.us/mlw/tundra/validation2005final_with_figures.pdf.Lilly, M.R., Paetzold, R.F. & Kane, D.L. 2008. Tundrasoil-water content and temperature data in supportof winter tundra travel. Proceedings of the <strong>Ninth</strong><strong>International</strong> <strong>Conference</strong> on Permafrost, Fairbanks,Alaska, June 29–July 3, 2008.38