Subsurface measurements on the McMurdo Ice Shelf, Antarctica

Abstract

In order to study the regimen of the McMurdo Ice Shelf three holes, 31, 32, and 57 m deep, were drilled near the seaward edge of the shelf; ice thicknesses at the drill sites were calculated to be 33, 48, and 94 m respectively. The rate of melting at the bottom of the shelf was found to be 1 m per year at two drill sites. The vertical density gradient in each of the holes is larger than that observed at Little America Station, and the density increases abruptly by about O· 1 g cm-" at the top of a brine-soaked layer which was estimated to be less than 6 m thick in each hole. Temperature profiles can be explained on the assumption that the brine moves horizontally through the shelf from the seaward edge to the interior and supplies heat to the shelf by convection and by liberation of latent heat during freezing. The observed brine level in the holes is about 20 percent lower than the hydrostatic level.

Stable isotope stratigraphy of ice cores and the age of the last eruption at Mount Melbourne, Antarctica

“…The surface accumulation rate would therefore not be greater than that at site 1 (2.2 m/a) and probably much lower because of the lower altitude and the sheltered location of site 1 by the parasite cone. Also, as tim ages and compacts, density increases; at the McMurdo Ice Shelf, a change from 0.4 to 0.8 Mg/m 3 was found to occur between 6 m and 30 m depth (Risk & Hochstein 1967). Thus, the upper 40 m of snow will be compacted so that the average annual accumulation rate will be less than the surface deposition rate and is estimated to be similar to the measured rate at site 2.…”

Hydrogen and oxygen isotope studies on the McMurdo Ice Shelf, Antarctica

“…7. This shows a schematic cross-section of the ice shelf along a flow line passing through site 207D, using data measured by Risk & Hochstein (1967). (An analogous diagram was given by Heine 1968).…”

“…The lower part of section 4 (21'56 to 21'95 m depth) has three peaks separated by 20 em of core. These "annual" core lengths have been converted to g cm-2 yr-1 by multiplying them by app::opriate values of the fim density, measured by Risk & Hochstein (1967). The values of annual accumulation obtained are then 47, 32, 18 and 16 g cm-2 yr-1 for sections 1, 2, 3 and 4 respectively.…”

“…Ice Shelf during the summers of 1965-66 and 1968-69 by Heine (1968) and Risk & Hochstein (1967). Firn core samples were collected using a Sipre auger, and were allowed to melt in plastic bags before storage.…”

“…1) are discussed in light of their isotopic compositions. (Risk & Hochstein 1967), directions of flow (Heine 1%7) and the equilibrium line separating the area of accumulation from the area of ablation (Swithinbank 1970). …”