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TitleGeological and meteorological controls on icing (aufeis) dynamics (1985 to 2014) in subarctic Canada
AuthorMorse, P DORCID logo; Wolfe, S AORCID logo
SourceJournal of Geophysical Research, Earth Surface 2015 p. 1-17, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20150011
Lang.English; French
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS85J; 85O
AreaGreat Slave Upland
Lat/Long WENS-116.0000 -114.0000 64.0000 62.0000
Subjectsgeophysics; Nature and Environment; hydrologic environment; ice; ice conditions; aufeis; climate, arctic; climatic fluctuations
Illustrationslocation maps; photographs; satellite images; plots; flow charts; histograms
ProgramClimate Change Geoscience Land-based Infrastructure
Released2015 09 07
AbstractIcings are widespread yet poorly understood winter hydrological phenomena that develop over the winter by freezing successive overflows of groundwater to the surface. Groundwater hydrology in arctic regions is constrained by geological setting and permafrost extent, and overflows are possibly driven by cold winters, winter warming intervals, high antecedent autumn rainfall, and low early winter snowfall. Consequently, icings are spatially recurrent but not necessarily annually nor to the same extent. We test the significance of identified meteorological forcing variables against a long-term data set of icing dynamics and distribution we developed for the Great Slave region around Yellowknife, Northwest Territories. Climate is regionally consistent, but variable geology and permafrost create hydrological conditions representative of much of the subarctic. We mapped 5500 icings in the study area (21,887?km2) with a semiautomated approach utilizing late spring Landsat archival images (1985 to 2014). Individual icing size, ranging 3 orders of magnitude (1.8?×?10-3?km2 to 4.1?km2), is related to return frequency. Infrequent ice (25% return frequency) accounts for 94% of the total icing area (86?km2). Winter warming intervals (=5°C; typically over 1–3?days) and autumn rainfall (September and October) explain 28% of icing density interannual variation overall. Interannual icing variation and significant meteorological forcing variables differ among ecoregions where varied geological settings and permafrost conditions influence the hydrological regime. Future icings may develop less frequently due to decreasing winter warming intervals, but increasing autumn rainfall may increase icing density where Canadian Shield leads to strong threshold-mediated runoff generation processes.
Summary(Plain Language Summary, not published)
Icings, a widespread yet poorly understood winter hydrological phenomena, are a potential hazard to northern winter- and all-season roads. Possibly forced by a number of meteorological conditions, icings recur at the same location, but not necessarily annually, nor to the same extent. In this first satellite-based study of long-term (1985 to 2014) icing dynamics, 5500 icings were mapped in the Great Slave region around Yellowknife, NT, and significant forcing conditions were determined. Icing size is directly related to return frequency, and 93% of icings return 25% of the time or less. Nearly a third of icing interannual variation is accounted for by periodic winter warm periods (warm waves) and autumn rainfall. However, this relation differs according to geological settings and permafrost conditions that influence the hydrological regime. Winter warm wave and autumn rainfall trends indicate a shift in future icing dynamics to generally less frequent, but larger icings.

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