The Amery Ice Shelf Ocean Research (AMISOR) project aims to examine and quantify processes involved in the interaction between the ice shelf, the interior grounded ice and the oceanic water masses that circulate beneath it. Two boreholes were melted through the shelf, within 100 km of the calving front, to access the ocean cavity. One (AM02) was at a site where it was believed that basal melt was occurring, and the other (AM01) was in a region with accreted marine ice. At both sites the summertime ocean structure revealed meltwater-modified boundary layers up to 100 m thick immediately beneath the shelf. Salinity and temperature data in the upper cavity at AM02 showed a strong seasonal cycle as a result of a combination of ice-shelf basal melt, and the intrusion of ocean water masses modified by sea-ice processes in Prydz Bay. At AM01, a 200m thick layer of marine ice underlay the meteoric ice, and showed an increase in salinity and decrease in stable-isotope fractionation with depth. The lowest 100m of marine ice was highly permeable, with a rectangular banded textural facies. Other preliminary results from this study are also reported.

The temperature profile in the 1200 m deep Dome Summit South (DSS) borehole near the summit of Law Dome, Antarctica, was measured in 1996, 3 years after the termination of the deep drilling.

The temperature profile contains information on past surface temperature over the last 4ka. This temperature history is determined by the use of a Monte Carlo inverse method in which no constraints are placed on the unknown temperature history and no solution is assumed to be unique. The temperature history is obtained from a selection of equally well-fitting solutions by a statistical treatment.

The results show that solutions covering the last 4ka have a well-developed central value, a most likely temperature history. The temperature record has two well-developed minima at AD 1250 and 1850. From 1850 to the present, temperatures have gradually increased by 0.7 K. The reconstructed temperatures are compared with the stable oxygen isotope (δ18O) from the DSS ice core.

A real-time video camera probe was deployed in a hot-water drilled borehole through the Amery Ice Shelf, East Antarctica, where a total ice thickness of 480 m included at least 200 m of basal marine ice. Down-looking and side-looking digital video footage showed a striking transition from white bubbly meteoric ice above to dark marine ice below, but the transition was neither microscopically sharp nor flat, indicating the uneven nature (at centimetre scale) of the ice-shelf base upstream where the marine ice first started to accrete. Marine ice features were imaged including platelet structures, cell inclusions, entrained particles, and the interface with sea water at the base. The cells are assumed to be entrained sea water, and were present throughout the lower 100-150 m of the marine ice column, becoming larger and more prevalent as the lower surface was approached until, near the base, they became channels large enough that the camera field of view could not contain them. Platelets in the marine ice at depth appeared to be as large as 1-2 cm in diameter. Particles were visible in the borehole meltwater; probably marine and mineral particles liberated by the drill, but their distribution varied with depth.

The variation of shear deformation rate with depth at the Dome Summit South (DSS) site, 4.7 km (~4 ice thicknesses) from the summit of Law Dome, East Antarctica, has been determined by repeated borehole inclination measurement. The results show that from the surface down to 1000m (ice-equivalent depth! deformation rates increase as expected with the increase in stress, temperature and the development of stronger ice-crystal fabrics. There is a broad maximum in strain rate around 1000 m. Below this depth, strain rates decrease, with values in the basal ice ~1/3 of those at 1000 m. in DSS, Holocene ice with low, uniform impurity levels extends to a depth of 1110 m, so the decrease in shear rale below 1000 m is attributed not to any change in properties of the ice, but to shear stress reduction induced by the large-scale retarding effect of local bedrock hills. Below 1000 m, with in the zone of retarded flow, there is a narrow spike, 14 m thick, in which the shear rate is ~5 times that in the ice immediately above and below. The shear-rate spike corresponds in depth to ice with high dust concentrations, small crystal size and strong vertical c-axis fabrics that was deposited at the Last Glaciol Maximum. A surface velocity of 1.98 ± 0.03 m a−1 obtained by integration of shear rate over the borehole depth is in agreement with the value of 2.04 ± 0.11m a−1 obtained by the global positioning system. The ratio of average column velocity to surface velocity determined by the borehole measurements is 0.74. A value of 0.76 is obtained from mass-balance considerations.