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Victoria University Antarctic Research Expedition Science and Logistics Reports 2002-03: VUWAE 47


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This project was designed both to investigate the little explored sub-ice shelf environment and to provide essential site data for coring 1000 m into the sea floor by ANDRILL for a history of the McMurdo-Ross Ice Shelf (MRIS). Ross Island has been depressing the crust under its own weight for at least the last million years, and at the same time has been acting as the western pinning point for the MRIS. As a result sediment has been accumulating in a sea floor depression over 900 m deep to the south of Ross Island in Windless Bight (Fig. 2). These sediments record the presence and possible past absence of the MRIS, and the movement of Ross Sea Shelf Water behind Ross Island between McMurdo Sound and the central Ross Sea

Proposed field activity

We proposed to occupy up to 4 sites on the McMurdo Ice shelf (Windless Bight area), first melting a 50-cm-wide hole through the ice shelf (70 to 150 m thick). We then proposed to measure water depth (expected to be over 800 m) and water column properties through a tidal cycle (conductivity, temperature, current speed, current direction) before sampling the sea floor by grab and gravity corer. At one or more sites a mooring to measure currents over several tidal cycles would be deployed and recovered. The access hole was to be melted by a Hot Water Drilling system provided by the Alfred Wegener Institute for Polar and Marine Research, which had been delivered by ship the previous summer.

Achieved activity

The project ran extremely well with access holes drilled and kept open through the ice shelf for up to 9 days (for a full account see the Logistics Report). This was critical for the success of the project. All instruments and sampling devices deployed through the access holes functioned and were recovered. The two most central of the 4 proposed sites were occupied, and a third site at the edge of the ice shelf monitored over a period of three weeks for currents in the upper 2/3 of the water column. The field operation to deploy the camp, drill and ream the access holes took longer than expected for the first site especially. In addition the techniques that we would trial to re-drill a hole and recover the frozen-in mooring were evaluated and it was decided that these required further development before this procedure would likely be successful. We decided to concentrate on two ice shelf holes setting short-term current moorings in both and a sea ice site where a mooring was deployed for 22 days.