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Geophysical Monograph Series




The dynamics of ice shelves

J. H. Zumberge and C. Swithinbank

Ice shelves are large floating ice sheets that flow under their own weight. Limited areas may be aground. They have a level or gently undulating surface. In the Antarctic, ice shelves vary in thickness from 200 to 1300 m. There is no generally preferred orientation of crystals. Fabric diagrams show isolated maxima of c-axes that may be of sedimentary origin, while four separate maxima are sometimes centered about the pole to the theoretical shear plane. There are fewer impurities than on land glaciers, though rock debris, spherules of extra-terrestrial origin, and brine have been encountered. Density varies from 0.3 gm cm−3 near the surface to 0.91 gm cm−3 at a depth of 155 m. While the temperature at 10-m depth varies from −9°C to −31°C, the bottom surface is always at the freezing point of sea water. Positive factors in the mass balance of an ice shelf are the accumulation of snow, inflow from land glaciers, and bottom freezing. Negative factors are calving, bottom and surface melting, the drifting of snow into the sea, and evaporation. Ice shelves are agents of erosion, transportation, and sedimentation. Till-like deposits containing marine fossils may have originated as submarine moraines laid down by the grounding of an ice shelf or by the release of material through bottom melting. Evidence of Pleistocene ice shelves should be sought among sediments of continental shelves lying within the boundary of Pleistocene ice sheets.

Citation: Zumberge, J. H., and C. Swithinbank (1962), The dynamics of ice shelves, in Antarctic Research: The Matthew Fontaine Maury Memorial Symposium, Geophys. Monogr. Ser., vol. 7, edited by H. Wexler, M. J. Rubin, and J. E. Caskey Jr., pp. 197–208, AGU, Washington, D. C., doi:10.1029/GM007p0197.

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