Climate and Permafrost 3 Ground temperature studies of permafrost growth at a drained lake site, Mackenzie Delta

• Main Authors: M. Burgess, A. Judge, A. Taylor, V. Allen
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Mackenzie Delta; Talik; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.573.8897; http://pubs.aina.ucalgary.ca/cpc/CPC4-3.pdf

investigate the growth of permafrost. Twenty-four boreholes were hydraulically drilled to depths ranging from 15 to 92 m below lake level and were instrumented with temperature cables. Monitoring of ground temperatures beneath the lake and surrounding shore-lines prior to drainage delineated a bow-shaped talik extending up to 32 m below lake bottom. Characteristics of the predrainage temper-ature profiles in the central lake holes were i) an upper unfrozen horizon in which temperatures reached a maximum of 2.S°C at roughly 5 m below lake bottom, ii) a permafrost table at depths of 20 to 32 m in the central part of the lake with consistently negative temperatures below, and iii) negative temperature gradients below the 5 m maximum temperature, averaging 50 mk/m in the permafrost section. Two years of post-drainage temperature monitoring revealed iv) that the former talik had completely frozen at nearshore sites (10 m thick or less), whereas, v) only 5 to 6 m of new permafrost had formed at central sites, and vi) in the unfrozen sections temperatures were close to O°C. A two-dimensional finite element computer simulation of the formation and growth of Illisarvik suggests a minimum lake age of 900 to 1000 years. Post-drainage conditions in the first year after drainage were modelled by studying the microclimatic regime together with the ground thermal regime. Although predicted profiles agreed well with measured temperatures, geotechnical and year-round weather