HR: 12:05h
AN: C12A-07    [Abstracts]
TI: Interactions of Multiple Factors in Creating Small Patterned-Ground Features Across the Arctic Bioclimate Gradient
AU: * Walker, D A
EM: ffdaw@uaf.edu
AF: Institue of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99709 United States
AU: Epstein, H E
EM: hee2b@virginia.edu
AF: Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904 United States
AU: Kuss, P
EM: Patrick.Kuss@unibas.ch
AF: Institute of Botany, University of Basel, Basel, CH-4056 Switzerland
AU: Michaelson, G J
EM: pngjm@uaa.alaska.edu
AF: University of Alaska Agriculture and Forestry Experiment Station, 533 E. Fireweed, Palmer, AK 99654
AU: Ping, C L
EM: pfclp@uaa.alaska.edu
AF: University of Alaska Agriculture and Forestry Experiment Station, 533 E. Fireweed, Palmer, AK 99654
AU: Raynolds, M K
EM: fnmkr@uaf.edu
AF: Institue of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99709 United States
AU: Romanovsky, V E
EM: ffver@uaf.edu
AF: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775 United States
AU: Tarnocai, C T
EM: tarnocaict@agr.gc.ca
AF: Ag. and Agri-Food Canada, 960 Carling Avenue, Ottawa, ONT K1A 0C6 Canada
AB: Small patterned-ground landforms are described along a bioclimate gradient in northern Canada and Alaska and summarized in tables and figures showing strength of influence of contraction cracking, differential frost heave, and vegetation - within five bioclimate subzones and four major soil texture classes. In the coldest parts of the Arctic (bioclimate subzones A and B), contraction cracking at small scales (10-30 cm between cracks) is the dominant process and contributes to the formation of hummocky terrain; differential frost heave has a small role here except in course rocky terrain where sorted circles are common. The presence of contraction cracks on all surfaces, wet and dry, and on all soil types indicate that the majority of the contraction cracks are caused by thermal processes and not desiccation. Larger mounds, apparently the result of differential frost heave, occur in some areas of Subzone B where there is more vegetation and peat. In the Middle Arctic (bioclimate subzone C), both small turf hummocks and well-developed non-sorted circles occur. Turf hummocks are dominant on hill slopes; erosion of the inter-hummock areas and accumulation of eolian material on the hummock tops creates taller hummocks. Non-sorted stripes occur on many slopes. In the northern Low Arctic (Subzone D), non-sorted circles are the most common features; and turf hummocks are restricted to small areas - generally steep snow beds. The centers of most frost boils are barren or partially vegetated in Subzone D. In the sourthern Low Arctic (Subzone E), the vegetation is very active and able to colonize and totally cover frost boils. Large vegetated mounds are apparently the remnants of once active frost boils. In areas with more clayey soils of subzones D and E, well-developed tightly packed mounds are common, and frost boils often occur on the tops of the mounds. The spacing of the mound centers is often 2-3 m. Mounds are also common south of treeline. Soil texture affects frost boil morphology and heave characteristics. In silty areas of northern Alaska non-sorted circles have annual differential heave in the order of 20 cm - apparently contributing to the strong patterning in many areas (spotted tundra in the Russian literature). Areas with sandy soil have little differential heave and no frost boils in areas of pure sand; whereas, areas with clayey soils have mound shaped frost boils with little annual heave. Vegetation plays a major role in defining the boundaries of the patterned-ground features, possibly affecting differential frost heave by decreasing the soil temperature and thickness of the active layer in the inter-circle areas; however, at two sites on sandy soils with well-developed non-sorted circles only minor differential soil heave was measured. The cause of the barren centers at these sites is probably unrelated to heave and may be due to the accumulation of salts within the frost-boils. Needle ice is another major contributing cause of barrenness on frost boils and appears to develop most strongly on saturated silts.
DE: 1851 Plant ecology
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting