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TitleMulti-decadal degradation and persistence of permafrost in the Alaska Highway corridor, northwest Canada
AuthorJames, M; Lewkowicz, A G; Smith, S L; Miceli, C M
SourceEnvironmental Research Letters vol. 8, no. 4, 2013 p. 1-10,
Alt SeriesEarth Sciences Sector, Contribution Series 20130081
PublisherIOP Publishing Ltd
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia; Yukon; Northwest Territories
NTS94A; 94G; 94H; 94I; 94J; 94K; 94M; 94N; 94O; 94P; 95A; 95B; 95C; 95D; 105A; 105B; 105C; 105D
AreaAlaska Highway; Fort St John; Whitehorse
Lat/Long WENS-136.0000 -120.0000 61.0000 56.0000
Subjectssurficial geology/geomorphology; environmental geology; geophysics; permafrost; freezing ground; ground ice; ground temperatures; climate effects; climate, arctic; climate; climate change; Cenozoic; Quaternary
Illustrationslocation maps; plots; tables
Programenvironmental impacts and adaptation in the northern environment, Environmental Geoscience
AbstractChanges in permafrost distribution in the southern discontinuous zone were evaluated by repeating a 1964 survey through part of the Alaska Highway corridor (56°-6°) in northwest Canada. A total of 55 sites from the original survey in northern British Columbia
and southern Yukon were located using archival maps and photographs. Probing for frozen ground, manual excavations, air and ground temperature monitoring, borehole drilling and geophysical techniques were used to gather information on present-day permafrost and
climatic conditions. Mean annual air temperatures have increased by 1.5-2.0° since the mid-1970s and significant degradation of permafrost has occurred. Almost half of the permafrost sites along the entire transect which exhibited permafrost in 1964 do so no longer.
This change is especially evident in the south where two-thirds of the formerly permafrost sites have thawed and the limit of permafrost appears to have shifted northward. The permafrost that persists is patchy, generally less than 15 m thick, has mean annual surface temperatures >0°, mean ground temperatures between -0.5 and 0°, is in peat or beneath a thick organic mat, and appears to have a thicker active layer than in 1964. Its persistence may relate to the latent heat requirements of thawing permafrost or to the large thermal offset of organic soils. The study demonstrates that degradation of permafrost has occurred in the margins of its distribution in the last few decades, a trend that is expected to continue as the climate warms.
Summary(Plain Language Summary, not published)
Thawing of permafrost can affect the terrain, hydrology and ecology of permafrost landscapes and infrastructure integrity. Information on current state and change in permafrost conditions is required for terrain sensitivity assessments and planning northern development (eg. pipeline, highway) to ensure infrastructure and environmental integrity. A 1964 survey was repeated in 2007-08 to evaluate changes in permafrost distribution in Alaska Highway corridor between Whitehorse and Fort St. John. Significant loss of permafrost has occurred coincident with rising air temperatures, especially in the southern portion of the study area. Results indicate that permafrost that persists is warm (near 0°C), less than 15m thick and largely associated with organic terrain. Warm permafrost likely remains due to the surface conditions and is 'ecosystem protected'. Permafrost in this region is sensitive to climate warming and to surface disturbance resulting from human activity.