New technique for access-borehole drilling in shelf glaciers using lightweight drills

This paper describes a new, environmentally friendly drilling technique for making short-and long-term access boreholes in shelf glaciers using lightweight drills. The new drilling technique was successfully developed for installation of small-diameter sensors under the Ross Ice Shelf through ~ 193 m thick ice at Windless Bight, McMurdo Ice Shelf, Antarctica. The two access boreholes were drilled and sensors installed in 110 working hours. The total weight of the drilling equipment including the power system and fuel is <400 kg. Installation of small-diameter sensors was possible for 1.8– 6 hours after penetration through the glacier into the sea water beneath. The new drilling technique does not require drilling fluid and therefore has minimal environmental impact. It should permit access through ice-shelf ice up to 350 m thick, or glaciers on grounded ice or subglacial lakes if there is no water-permeable interface at the base. Modifications, presented in this work, of the drilling equipment and protocol will allow for (1) ~ 21 working hours for penetration through 200 m of ice, (2) installation of sensors up to 120 mm in diameter and (3) drilling long-term open boreholes through 400 m thick ice in 100 working hours.