Investigation of Ice Pressure on Dams. First Report on Measurement of Coefficient of Linear Expansion of Artifical and Natural Ice. J. G. Willmot Hydro-electric Power Commission of Ontario. Research Division Report No. 56–392, 1956, 41 pages, illus
J. F. Nye
Journal of Glaciology
REVIEWS 149 discussion of the thermal economy and structure of the Ice and finally the role of the unique blizzards of Adelie Land. 270 radiation measurements were made at Port Martin and a smaller number on the inland ice. Both series were much interrupted by the blizzards of this formidable area: at the Adelie Land coast the average wind speed over the year is of gale force. The snow surface with its high albedo has a small intake of radiation and, owing to the small vapour content of the
... a relatively strong loss. With clear sky at Port Martin there is a net loss of radiation from the surface with sun heights up to 27 degrees; on the inland ice, with still higher albedo, with sun heights up to 40 degrees. There is radiation loss at Port Martin normally from the end of March to mid November, but a gain at times in the summer period. At lat. 80° S. a net radiation loss was found in every month, and Loewe considers this typical of the Antarctic Ice Sheet. The average radiation loss from the ice cap appears to be 36 kg. calories per cm. 2 per annum. The author calculates from a mean meridional (i.e . southerly) wind component averaged through the depth of the troposphere of 2·9 knots at the edge of the Antarctic Ice Sheet that eight days would be a normal time spent by the air in crossing Antarctica. It is difficult to judge the representativeness of such a figure. The average cooling of the air layer in eight days over the inland ice would be 14° C. Temperatures were taken at 1·5 and 20 cm. below the snow/ ice surface. At Port Martin, except with very high sun or low overcast, the temperatures at I cm. depth were lower than at 5 cm. On the inland ice, the temperatures at I cm. depth were in all circumstances lower than those at 5 cm. even at mid summer with the sun high. The snow surface at Port Martin and at lat. 80° S. is on average colder than the air above it. The winds are predominantly southerly; nevertheless a surface inversion is the normal condition. The firn temperatures at depths down to la m. were measured in narrow bore-holes up to 200 miles (320 km .) inland . At lat. 67° S. and 1,000 m. as!. a yearly mean temperature of -21° C. was indicated and at lat. 69 ° S. and 2,000 m. as!. -34°C. The inland ice in Adelie Land is considered by Loewe probably to be frozen right down to bedrock south of lat. 70° S., but faster-moving glacier tongues may thaw the ground underneath by heat generated through friction. The amount of snow carried in the blizzards was measured in drift traps 50 cm. above the surface. The yearly mean at this height was 50 gm. carried through a vertical plane of one square centimetre each hour. The wind direction in Adelie Land is almost always south or south-east. This suggests a total transport outwards over each metre of the Adelie Land coast of 20,000 tons of snow yearly-probably removing half, possibly more than all, the snow which falls in the coastal belt up to 100 to 150 miles (160-240 km.) inland in this sector. In the reviewer's opinion it is unlikely that the quantities of snow removed by blizzards in other sectors are commensurate with the extreme conditions of Addie Land . The question of whether the great Ice Sheet in east Antarctica is receiving adequate nourishment for its full maintenance at the present epoch remains open, but Loewe's study is an important contribution to our assessment of this in a specially interesting sector.