BAS hot water drilling on Ronne Ice Shelf, Antarctica

The British Antarctic Survey (BAS) has developed a hot water drilling system that was successfully used during the Antarctic summers of 1990/91 and 91/92 to penetrate ice 562m and 541m deep on Ronne Ice Shelf, Antarctica. The hot water drill currently incorporates 300kW of heating power with a water recirculation system, removing the need for continuous snow melting while drilling. In total, approximately four tonnes of aviation fuel were burned at each of the two sites, allowing a hole 0.2-0.25m in diameter to be drilled over a period of 1 to 3 days, and maintaining it, through repeated reaming, for a further five days. Ice temperatures of -26℃ caused rapid refreezing of the hole and successive borehole caliper profiles indicated initial closure rates of 11mm hr^-1,decreasing to 5mm hr^-1 after the hole had been open for a number of days. Access to the sub-ice shelf oceanographic environment allowed measurements to be made in the underlying seawater and the installation of thermistors in the ice and the ocean for long term temperature monitoring. In forthcoming field work, the drill will be used to penetrate ice approximately 850m thick to gain access to the underlying seawater and deploy a string of oceanographic instruments with a diameter of 0.14m, necessitating further improvements in the drill's reliability and performance.