Abstract:
Surface elevation and movement of the McMurdo Ice Shelf and Ross Ice Shelf were conducted as part of the McMurdo Ice Shelf Project which was active from the 1962 to 1970 field seasons. A significant amount of field data was collected. Resection observations were made from 69 stations over the study period. The stations were installed during the 1962/63 field season and at each marker position, ... four accumulation bamboos were placed, about 50 yards out at the four points of the compass from the marker. Not all stations were used each season. (A resection survey is where from an unknown point three directions are measured to three known features to fix a position. GPS is now used for this purpose). Stain lines stations were set out in the 1964/65 season. This network only gave parameters in three directions. After two seasons of measurements and calculating the maximum compression and extension directions, it was decided to extend the network to give strain characteristics in six directions. These measurements were used to determine the speed and direction of movement of the two ice shelves and accurately plot the merging flow lines between the two ice shelves. In addition to these two main measurements, a number of other investigations were simultaneously carried out including 0-2 metre pit stratigraphy, 10 meter deep temperature profiles, 0.10 meter density profiles, brine infiltration investigations, Pram Point Pressure Roller investigations, strain/density relationships in the ice, speed and direction of the movement of the ice shelf and surface accumulation and ablation measurements. Leveling of the ice shelf was conducted each year. The leveling was used to produce contour maps of the McMurdo Ice Shelf area. In the 1963/64 season, a profile was laid out across three pressure rollers north of Pram Point. The pressure rollers were resurveyed every year for strain line measurements. Panorama photos of the rollers were photographed from established survey points. In the 1965/66 season, a number of density profiles in the southern part of the Ice Shelf, between White and Black Island and along the ablation in a number of places, up to 15 miles from the ice front were carried out. It was found that at a certain density, the brine had been forced out of the ice matrix. Samples of pure brine were brought back to New Zealand for analysis. To obtain further information on the distribution and physical characteristics of the sea water infiltration into the McMurdo Ice Shelf, a number of drill holes were made along the western edge of the shelf in the 1967/68 season. Samples of the clear brine at the bottom of the drill holes were obtained as well as samples of the lower cores. Temperature measurements were taken also. It was hoped that the brine samples would provide information about any changes in the sea water as it infiltrates through the snow layers. In the 1966/67 a fifty mile thickness measuring traverse was conducted across the McMurdo Ice Shelf. From 1970 to 1982 all measurement and calculations were conducted by the New Zealand Lands and Survey Department. Velocities of the Pram Point pressure rollers were measured in the 1979/80 and 1982/83 season. A detailed analysis of all measurements was conducted after remeasurements in the 1982/83 season.
