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TitleDistribution and activity of ice wedges across the forest-tundra transition, western Arctic Canada
AuthorKokelj, S V; Lantz, T C; Wolfe, S A; Kanigan, J C; Morse, P D; Coutts, R; Molina-Giraldo, N; Burn, C R
SourceJournal of Geophysical Research vol. 119, issue 9, 2014 p. 2032-2047, https://doi.org/10.1002/2014jf003085
Year2014
Alt SeriesEarth Sciences Sector, Contribution Series 20130468
PublisherAmerican Geophyiscal Union
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS107B; 107C
AreaMackenzie River Delta; Richards Island; Garry Island
Lat/Long WENS-136.0000 -133.0000 69.7500 68.4167
Subjectssurficial geology/geomorphology; ice wedges; remote sensing; ground temperatures; ground ice; vegetation; permafrost; thermal contraction
Illustrationsphotographs; location maps; tables; graphs; plots
ProgramLand-based Infrastructure, Climate Change Geoscience
AbstractRemote sensing and a regional network of ground-temperature and ground-ice observations have been used to investigate the size and distribution of ice wedges in different soil types across the tree line in uplands east of the Mackenzie Delta. In the northern most dwarf-shrub tundra, up to 50% of the ground surface is polygonal, with ice wedges commonly exceeding 3 m in width. The largest ice wedges are in peatlands where thermal-contraction cracking occurs more frequently than in nearby hummocky terrain with fine-grained soils. There are fewer ice wedges, rarely exceeding 2-m in width, in uplands to the south, and none have been found in mineral soils of the tall-shrub tundra, although active ice-wedges are found there throughout peatlands. In the subarctic forest, relict wedge ice is restricted to peatlands where the saturated organic active layers above permafrost may not freeze back each year. At tundra sites, winter temperatures at the permafrost surface are lower in organic than mineral soils because of the shallow permafrost table and high thermal conductivity of frozen peat. In combination with the high coefficient of thermal contraction of ice in the highly porous peat, ice-wedge cracking and growth is more common in peatlands than in mineral soil. However, the high volumetric water content of a saturated organic active-layer may inhibit freezeback, particularly where thick snow accumulates, making the permafrost in polygonal peatlands susceptible to degradation following the alteration of drainage or climate warming.
Summary(Plain Language Summary, not published)
We examined the size and distribution of ice wedges in different soil types across the tree line in uplands east of the Mackenzie Delta. These are largest in peatlands in the north, where thermal-contraction cracking occurs most frequently. They are smaller and fewer in the southern tundra, with active ice wedges found only within peatlands. In the subarctic forest, only relict wedge ice is found and is restricted to peatlands. Ice-wedge cracking and growth is more common in peatlands than in mineral soil. However, the high volumetric water content of saturated peat may inhibit freezeback, particularly where thick snow accumulates, making permafrost in polygonal peatlands susceptible to degradation following the alteration of drainage or climate warming.
GEOSCAN ID293674