Snow Cover and Ground Temperatures, Garry Island, N.W.T.

Field measurements of the influence of snow on ground temperatures, at a depth of 90 cm., were carried out during 1968-73 at Garry Island, N.W.T. The results show that the ameliorating effect of snow can be expressed by a regression equation. The side slopes tend to have the highest mean annual temperatures; the flats the lowest; and the ridges intermediate. At Garry Island, where permafrost is thick, variations in snow cover are probably not reflected in the position of the bottom of permafrost. By contract, in the nearby alluvial islands of the Mackenzie Delta, where permafrost is thin, the effects of snow on the position of the lower permafrost surface are probably considerable

Deformation by Glacier-Ice at Nicholson Peninsula, N.W.T., Canada

Two excellent examples of sediments deformed by glacier ice occur on Nicholson Peninsula, Mackenzie District (Liverpool Bay, 69 54 N, 129 W). Sediments, topography and structure of the Peninsula are described. Altitudes in the hilly northern half attain 200-300 ft. above sea level, whereas those in the south rarely exceed 30 ft. The hills were formed either by glacier ice moved against a topographic obstruction, resulting in a large push moraine, or by the drag effect of ice moving over weak strata. Deformation could have occurred during the last ice advance or earlier, probably in a single period of deformation, but whether the ground was frozen at the time is not evident

Notes on the Shoreline Recession Along the Coast of the Yukon Territory

The 150-km.-long stretch of the coast between Herschel Island and the Mackenzie Delta terminates in bluffs cut into Pleistocene silts, sands, and gravels. No bedrock has yet been observed; if present, its occurrence must be very local. The coastal bluffs which are up to 50 m. high, are constantly being undermined by waves and by the melting of numerous thick tabular ground-ice sheets lying close to sea-level. As the ice sheets are found only in fine-grained sediments, coastal retreat is especially rapid long silty to clayey bluffs. Similarly rapid recession has taken place along the northern coast of Alaska and from the Mackenzie Delta east to Langton Bay. It is the purpose of this note to describe some of the geomorphological and historical evidence fo recession of the coast of the Yukon Territory. The field observations were made while the writer was carrying out studies for the Geographical Branch, Department of Mines and Technical Surveys, Ottawa

Permafrost Depths, Lower Mackenzie Valley, Northwest Territories

Reports 1965-66 ground temperature records for seven new sites established in the lower Mackenzie valley, indicating permafrost thickness of about 350 ft for Arctic Red River, 400 ft in site 14 mi west of Fort McPherson, 350 ft or more in the south central Mackenzie Delta, and 60-100 ft at four sites in the outer Delta which are within two feet of sea level. In the distal part of the Delta, where new islands are growing, perma- frost is aggrading downwards in the saturated alluvial soils.Profondeurs du pergélisol, basse vallée du Mackenzie, T.N.-O. Au moyen de cables à thermistor installés dans des puits sismiques forés à cette fin, on a relevé les températures dans le sol pour sept sites de la basse vallée du Mackenzie, pour la période de 1965 à 1966. A partir de ces premières mesures, on estime l'épaisseur du pergélisol à environ 350 pieds (120 m) pour Arctic Red River et à 400 pieds (135 m) pour un site localisé à 14 milles (23 km) à l'ouest de Fort McPherson. Dans la partie sud-centrale du delta, zone de chenaux mouvants et de lacs en voie de comblement, l'épaisseur est de 350 pieds (120 m), ou peut-être plus. Dans la partie digitée du delta, où de nouvelles îles se forment, le pergélisol progresse en profondeur dans les matériaux, le pergélisol peut n'avoir que de 60 à 100 pieds (20 à 34 m) d'épaisseur : il devrait continuer à y progresser encore pendant plusieurs siècles

Aklisuktuk (Growing Fast) Pingo, Tuktoyaktuk Peninsula, Northwest Territories, Canada

Field surveys have been carried out for the 1972 to 1979 period in order to study the growth of Aklisuktuk (Growing Fast) Pingo. The field surveys show that the top of the pingo was slowly subsiding during the seven-year survey period, possibly from a slow downslope glacier-like creep of the ice-rich overburden and ice core. The name "Aklisuktuk" probably dates back at least 200 years. The rapid growth which attracted attention was from accumulation of water in a large sub-pingo water lens.Key words: Aklisuktuk Pingo, sub-pingo water lens, pingo subsidenceMots clés: Pingo Aklisuktuk, poche d'eau au-dessous du pingo, affaissement du ping

The Birth and Growth of Porsild Pingo, Tuktoyaktuk Peninsula, District of Mackenzie

The birth and growth of Porsild Pingo (ice-cored hill) can be taken as fairly representative of the birth and growth of the more than 2000 closed-system pingos of the western arctic coast of Canada and adjacent Alaska. Porsild Pingo, named after a distinguished arctic botanist, has grown in the bottom of a large lake that drained catastrophically about 1900. Porsild Pingo has grown up at the site of a former shallow residual pond. The "birth" probably took place between 1920 and 1930. The high pore water pressure that caused updoming of the bottom of the residual pond to give birth to Porsild Pingo came from pore water expulsion by downward and upward permafrost growth in saturated sands in a closed system. In the freeze-back period of October-November 1934, permafrost ruptured and the intrusion of water into the unfrozen part of the active layer grew a 3.7 m high frost mound photographed by Porsild in May 1935. Porsild Pingo has grown up at, or very close to, the site of the former frost mound. The growth of Porsild Pingo appears to have been fairly steady from 1935 to 1976, after which there has been a decline to 1987. The growth rate has been nearly linear with height, from zero at the periphery to a maximum at the top. The present addition of water to the pingo is about 630 cu m/y. Providing there is no major climatic change. Porsild Pingo may continue to grow for a few centuries.Key words: frost mound, intrusive ice, permafrost, pingo, PorsildMots clés: monticule de gel, glace d’intrusion, pergélisol, pingo, Porsil

Development of a best practice statement on the use of ankle-foot orthoses following stroke in Scotland

A National Health Service Quality Improvement Scotland (NHS QIS) scoping exercise in 2007 identified the use of ankle-foot orthoses (AFOs) following stroke as a clinical improvement priority, leading to the development of a best practice statement (BPS) on AFO use after stroke. This paper outlines the development process of the BPS which is available from NHS QIS. The authors were involved in the development of the BPS as part of a working group that included practitioners from the fields of orthotics, physiotherapy, stroke nursing and bioengineering, and staff of NHS QIS and a patient representative. In consultation with an NHS QIS health services researcher, the authors undertook a systematic literature review to evidence where possible the recommendations made in the BPS. Where evidence was unavailable, consensus was reached by the expert working group. As the BPS was designed for the non-specialist and non-orthotic practitioner the authors also developed educational resources which were included within the BPS to aid the understanding of the principles underpinning orthotic design and prescription. The BPS has been widely distributed throughout the health service in Scotland and is available electronically at no cost via the NHS QIS website. At part of an ongoing evaluation of the impact of the BPS on the quality of orthotic provision, NHS QIS has invited feedback regarding successes and challenges to implementation