HR: 17:30h
AN: C24A-07    [Abstracts]
TI: The structure and dynamics of earth hummocks in the subarctic forest near Inuvik, Northwest Territories, Canada.
AU: * Kokelj, S V
EM: kokeljsv@inac.gc.ca
AF: Water Resources Division, Department of Indian Affairs and Northern Development, PO Box 1500, Bellanca Building, Yellowknife, NT X1A 2R3 Canada
AU: * Kokelj, S V
EM: kokeljsv@inac.gc.ca
AF: Department of Geography and Environmental Studies, Carleton University, 1125 Colonel By Drive, Ottawa, Ont K1S 5B6 Canada
AU: Burn, C R
C24A-07 AF: Department of Geography and Environmental Studies, Carleton University, 1125 Colonel By Drive, Ottawa, Ont K1S 5B6 Canada
AU: Tarnocai, C
C24A-07 AF: Agriculture and Agi-food Canada, K.W. Neatby Building, 960 Carling Avenue, Ottawa, Ont K1A 0C6 Canada
AB: The surface micro-relief, permafrost table configuration, ground-ice, and soil organic-matter contents are described for collapsed and poorly-developed mud hummocks and well-developed vegetated hummocks near Inuvik, N.W.T. The diameters of collapsed earth hummocks were significantly greater than those of vegetated hummocks. Mean minimum and maximum hummock relief and interhummock distance increased along the continuum of forms, with well-developed vegetated hummocks characterized by the widest spacing and greatest relief. A bowl-shaped permafrost table mirrored the surface relief of the poorly-developed and well-developed hummocks, whereas collapsed hummocks were underlain by a planar or concave down permafrost table. Segregated ice lenses oriented parallel to the permafrost table and small bodies of intrusive ice were observed beneath the developing and well-developed hummocks. Statistical relations between the configuration of the permafrost table and hummock relief, long-term observations of active-layer and hummock change, and hummock response to surface manipulation indicate that development of a bowl-shaped permafrost table and near-surface ground ice can thrust soils radially both inward and upward causing hummock growth, whereas thaw subsidence can result in outward spreading and hummock collapse. Reaction-wood rings in black spruce trees growing on hummocky terrain indicate that tree tilting was associated with organic accumulation in interhummock areas, active-layer thinning, aggradational-ice development and hummock growth. Cessation of reaction wood coincided with a period of active-layer deepening, degradation of ground ice and outward spreading of the hummocks. In subarctic forests, hummock dynamics can be driven by ecological change associated with the fire cycle and climate change.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1630 Impacts of global change (1225)
DE: 1827 Glaciology (0736, 0776, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005