Vegetation colonization of permafrost\u2010related landslides,Ellesmere Island, Canadian High Arctic

Relationships between vegetation colonization and landslide disturbance are analyzed for 12 active\u2010layer detachments of differing ages located in three areas of the Fosheim Peninsula, Ellesmere Island (80\ub0N). We discuss vegetation as an age index for landslides and a way to assess the time needed for complete recolonization of the surfaces since landslide detachment. Vegetation on undisturbed terrain is similar in the three areas but is more highly developed and complex inland due to a warmer summer climate. On a regional scale, the location of the area is as important as the effect of landslide age on vegetation colonization because of the influence of mesoclimatic conditions on vegetation development. On a landscape scale, there is a positive relationship between landslide age and vegetation development, as represented by total vegetation cover, floristic composition, and successional stage. Consequently, vegetation can be used at this scale as an indicator of landslide age. Fifty years are required to restore vegetation patches to a floristic composition similar to communities occurring in undisturbed conditions, but with lower floristic richness and a discontinuous cover and without well\u2010developed layering. The shorter time needed for landslide recovery in the area with the warmest summer climate confirms the sensitivity of arctic vegetation to small differences in air temperature. This could trigger a set of interlinked feedbacks that would amplify future rates of climate warming

CANADIAN LANDFORM EXAMPLES ‐ 17 RETROGRESSIVE THAW SLUMPS

Retrogressive thaw slumps are the most active geomor‐phic features of permafrost terrain (NRC 1988). Also called ground‐ice slumps (Mackay 1966), they consist of a layer of ice‐poor overburden, an ice‐rich face and a low‐angle mudflow downslope (figures 1 and 2). They are common along northern rivers and lakeshores and the western Arctic coast. Some have been initiated by terrain disturbance associated with road construction and mineral exploration (Lambert 1972). Insulation of ice‐rich slopes (e.g., using woodchips) may reduce thaw slumping. Initially, this appears to have been successful along the pipeline route from Norman Wells, NWT, to Zama, Alberta. Copyrigh

Thermal state of permafrost in North America: A contribution to the international polar year

A snapshot of the thermal state of permafrost in northern North America during the International Polar Year (IPY) was developed using ground temperature data collected from 350 boreholes. More than half these were established during IPY to enhance the network in sparsely monitored regions. The measurement sites span a diverse range of ecoclimatic and geological conditions across the continent and are at various elevations within the Cordillera. The ground temperatures within the discontinuous permafr

Variability and change in the Canadian cryosphere

During the International Polar Year (IPY), comprehensive observational research programs were undertaken to increase our understanding of the Canadian polar cryosphere response to a changing climate. Cryospheric components considered were snow, permafrost, sea ice, freshwater ice, glaciers and ice shelves. Enhancement of conventional observing systems and retrieval algorithms for satellite measurements facilitated development of a snapshot of current cryospheric conditions, providing a baseline against which future change can be assessed. Key findings include: 1. surface air temperatures across the Canadian Arctic exhibit a warming trend in all seasons over the past 40 years. A consistent pan-cryospheric response to these warming temperatures is evident through the analysis of multi-decadal datasets; 2. in recent years (including the IPY period) a higher rate of change was observed compared to previous decades including warming permafrost, reduction in snow cover extent and duration, reduction in summer sea ice extent, increased mass loss from glaciers, and thinning and break-up of the remaining Canadian ice shelves. These changes illustrate both a reduction in the spatial extent and mass of the cryosphere and an increase in the temporal persistence of melt related parameters. The observed changes in the cryosphere have important implications for human activity including the close ties of northerners to the land, access to northern regions for natural resource development, and the integrity of northern infrastructure. \ua9 2012 UKCrown: Environment Canada; \ua9 Her Majesty the Queen in Right of Canada.Peer reviewed: YesNRC publication: Ye