Development of a clean hot water drill to access Subglacial Lake CECs, West Antarctica

Abstract

Recent drilling successes on Rutford Ice Stream in West Antarctica demonstrate the viability of hot water drilling subglacial access holes to depths >2000 m. Having techniques to access deep subglacial environments reliably paves the way for subglacial lake exploration beneath the thick central West Antarctic Ice Sheet. An ideal candidate lake, overlain by ~2650 m of ice, identified by Centro de Estudios Científicos (CECs), Chile, has led to collaboration with British Antarctic Survey to access Subglacial Lake CECs (SLCECs). To conform with the Scientific Committee on Antarctic Research code of conduct, which provides a guide to responsible scientific exploration and stewardship of these pristine systems, any access drilling must minimise all aspects of contamination and disturbance of the subglacial environment. To meet these challenges, along with thicker ice and 2000 m elevation, pumping and water treatment systems developed for the Subglacial Lake Ellsworth project, together with new diesel generators, additional water heating and longer drill hose, are currently being integrated with the BEAMISH hot water drill. A dedicated test season near SLCECs will commission the new clean hot water drill, with testing and validation of all clean operating procedures. A subsequent season will then access SLCECs cleanly.

The BEAMISH hot water drill system and its use on the Rutford Ice Stream, Antarctica

“…The access holes created allowed the recovery of sediment samples from the ice stream using samplers on the drill nozzle or from the bed using a simple sediment corer (Makinson, 2021) as well as the in-ice installation of a range of monitoring instrumentation to aid in describing ice-sheet dynamics (Smith, 2020). Disturbance of the basal sediment was also minimised by the ability to manage the borehole water level at breakthrough.…”

“…Sediment sampling was attempted in the borehole (Fig. 23F) using a new hammer arrangement (Makinson, 2021). While the new mechanism operated successfully, no indication of penetration was noted during the hammering process and, following recovery, damage to the corers' cutter head suggested that a boulder of some description was the probable cause of the obstruction (Smith, 2020).…”

“…Following refreezing of the borehole, the plough is forced through the sediment by the downstream ice movement, with integrated strain gauges inferring shear properties of the sediment. A sampling of the sediment is carried out using a standard gravity corer with hammering mechanism (Makinson, 2021), recovering 63 mm diameter samples. Tiltmeters in discrete pressure housings are deployed in strings of multiple instruments within the ice borehole.…”

Non-contact measurement system for hot water drilled ice boreholes

“…The next field testing opportunity for the BMS will be during the planned test season for the Subglacial Lake CECs (Centro Estudios Cientificos) Clean Hot Water Drill project (see Makinson and others, 2021). This project will primarily require the hole diameter measurements, however the full functionality would be beneficial.…”

A new percussion hammer mechanism for a borehole deployable subglacial sediment corer

“…The key attributes of this new mechanical percussion hammer mechanism are its unrestricted operational depth range, relatively simple operation, reduced learning curve and easy field maintenance, which extends the usefulness of the BAS-UWITEC coring system particularly in remote field environments where it is prohibitive to use larger drilling infrastructure. In preparation for the planned clean accessing of Subglacial Lake CECs in West Antarctica (Makinson and others, 2021) and sampling of its sediments almost 3000 m below the ice-sheet surface, further modifications to the corer hammer section and tether are required. The modifications are necessary to conform to stringent cleanliness standards in preventing chemical or biological contamination of the subglacial lake environment.…”