Depth Hoar Formation Research Articles

Snowfall and Oxygen-Isotope Variations off the North Coast of Ellesmere Island, N.W.T., Canada

AbstractSnow-pack along the land-fast ice fringe off the north coast of Ellesmere Island was generally characterized by depth-hoar overlain by dense snow and wind slab. Mean snow depth in the study area was 0.54 m (1982-85) and the mean δ18O value of the snow-pack was -31.3˚/00. Isotope data were not obtained previously for this geographic region and, therefore, complement a previous study of δ18O variations in High Arctic snow (Koerner, 1979). The data are consistent with an Arctic Ocean moisture source. The δ18O profiles show seasonal variations, with winter snow being more depleted in 18O than fall and spring snow. However, the δ18O profiles are dominated by a trend to higher δ18O values with increasing depth. This is attributed to a decrease in δ18O values as condensation temperatures fall during the autumn-winter accumulation period. During this time, there is also a change from relatively open to almost complete ice cover in the Arctic Ocean. The change in evaporation conditions and consequent effect on δ values gives rise to a sharp discontinuity in the δ18O profiles and a bi-modal δ18O frequency distribution. The bi-modal distribution is reinforced by a secondary isotope fractionation that occurs during depth-hoar formation. This isotope effect leads to a wider δ18O range but does not significantly alter the mean δ18O value.

Studies on Structures and Physical Properties of Snow on Mizuho Plateau, Antarctica

Relations between structures and physical properties of snow of four 30-m cores in Mizuho Plateau, Antarctica were investigated by measuring their specific areas of internal free surfaces and air permeabilities. The specific area of internal free surfaces and the air permeability decreased with increasing depth. Both of the depth profiles showed a kink at a depth of a critical density 550 kg/m3, indicating a change in the physical mechanism of densification. The drastic decrease of the specific areas above the depth of the kink was considered to be mainly caused by rounding and growth of ice particles; the gradual decreases below the kink were attributed to the development of bonding and particles.Measured air permeability was compared with the theoretical one for randomly packed powders of uniformly sized solid particles. The discrepancy between the measured and theoretical permeabilities was explained by the change in shapes and sizes of air channels in the snow. The depth hoar formation, which was active in regions with smaller accumulation of snow, was considered to result in the favorable shapes of channels for air permeation.

Studies on Structures and Physical Properties of Snow on Mizuho Plateau, Antarctica

Relations between structures and physical properties of snow of four 30-m cores in Mizuho Plateau, Antarctica were investigated by measuring their specific areas of internal free surfaces and air permeabilities. The specific area of internal free surfaces and the air permeability decreased with increasing depth. Both of the depth profiles showed a kink at a depth of a critical density 550 kg/m3, indicating a change in the physical mechanism of densification. The drastic decrease of the specific areas above the depth of the kink was considered to be mainly caused by rounding and growth of ice particles; the gradual decreases below the kink were attributed to the development of bonding and particles. Measured air permeability was compared with the theoretical one for randomly packed powders of uniformly sized solid particles. The discrepancy between the measured and theoretical permeabilities was explained by the change in shapes and sizes of air channels in the snow. The depth hoar formation, which was active in regions with smaller accumulation of snow, was considered to result in the favorable shapes of channels for air permeation.

Upward flux of vapor from frozen materials in the High Arctic

This study demonstrates the formation of depth hoar by upward vapor transport from frozen soils in the Canadian High Arctic. The saturated boggy site produced more hoar than the non-saturated gravelly site nearby but, compared with interior Alaska, the amount produced was one order of magnitude less. The difference is attributed mainly to the reduced soil temperature gradient in a cold, polar environment which is less favorable to vapor transfer.

Six-year record of oxygen and hydrogen isotope variations in South Pole firn

Direct measurements of snow accumulation at stakes near the South Pole over a 6-year period (1958–1963) provide an unusual opportunity to check the reliability of accumulation and annual-layer determinations by stratigraphic and isotopic methods. The results are gratifying. Agreement between interpretations based on stratigraphic and isotopic data is excellent, and both are consistent with accumulation-stake measurements in nearly all respects. All three procedures indicate an average annual accumulation of 7 cm of water at the South Pole over the 1958–1963 interval. Isotope data suggest that depth-hoar formation may result in relative enrichment in O18. This could come about through partial recondensation of vapor generated within the depth-hoar layer accompanied by escape of residual vapor impoverished in O18.