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. 3-D geothermal model. Snowdrifts A to K.Figure 4. 2-D section of predicted ground temperatures underneatha road embankment and a thick snowdrift in January 2100. Thedotted lines are the ground temperatures for a thin snow cover.Figure 3. Ground temperature difference between the simulationswith snowdrift surface conditions and the bare surface: (A) InJanuary 2005; (B) In January 2100.The 3-D geothermal model for the month of January 2005in the valley of Salluit is shown in Figure 2. Among the snowdriftsmapped in the valley, 11 were integrated in the model.They are identified with letters from A to K in Figure 2.Several numerical simulations were performed forassessing the thermal effect of snowdrifts. The groundtemperature difference between the simulations integratingthe snowdrift surface conditions and without integratingthese conditions is shown in Figures 3a and 3b in January2005 and 2100, respectively. Ground temperature differencesbelow the cutoff value of 0.5 C are not shown. In 2005, thethermal effect of snow insulation on ground temperaturescan reach depths as high as 100 m except for the snowdriftsA (16 m), F (42 m) and J (56 m). The surface area ofsnowdrift A is small, restricting the depth of snow influenceon ground temperatures. For similar snowdrift surface area,till and sand transmit the heat more efficiently than clay dueto their higher thermal conductivity and their lower watercontent. The thermal effect of snow on ground temperaturesis limited, therefore, under the snowdrifts F and J comparedto snowdrift H (Fig. 3a) due to the difference in soil types.In 2100, the climate warming will lead to a reductionin temperature difference at the surface: 10°C (Fig. 3b)instead of 20°C (Fig. 3a). The ground volume affected bythe snowdrifts will also decrease. In a context of climatewarming, the ground temperatures affected by a thin snowcover or under bare surface conditions will increase fasterthan the ground temperatures beneath snowdrifts.A 2-D section of predicted ground temperatures underneatha road embankment and a thick snowdrift lying on the rightembankment shoulder is shown in Figure 4 to illustrate themajor thermal effect of snowdrift. A 4 m thick talik is presentbeneath the snowdrift, while the talik is only 1 m whenconsidering a thin snow cover (dotted lines). The thermaleffect of the snowdrift propagates also underneath the roadembankment, inducing a ground warming. However, noattempt was made to take into account the water migrationat shallow depths and to accommodate thaw settlement.These two factors can influence the geothermal field ofpermafrost.ReferencesGoodrich, L.E. 1982. The influence of snow cover on theground thermal regime. Canadian GeotechnicalJournal 19: 421-432.IPCC 2000. Special Report on Emission Scenarios.N. Nakicenovic & R. Swart (eds.). UK: CambridgeUniversity Press, 570 pp.Luetschg, M., Bartelt, P., Lehning, M. & Toeckli, V. 2003.Numerical simulation of the interaction processesbetween snow cover and alpine permafrost.Proceedings of the Eighth <strong>International</strong> <strong>Conference</strong>on Permafrost, Zurich, Switzerland: 697-702.Music, B. & Caya, D. 2007. Evaluation of the hydrologicalcycle over the Mississippi river basin as simulatedby the Canadian Regional Climate Model. Journal ofHydrometeorology 8(5): 969-988.172