Document Actions
Entry Technologies
Current technologies are capable of drilling access holes through 4000 meters of ice with suitable adaptations. There are three methodologies that might be used to access subglacial systems:
-
ice corers;
-
thermo-probes; and
-
hot water drills.
Each of these techniques has advantages and disadvantages. Ice coring is an established method that has accessed the base of ice sheets. The main goal of ice coring is to extract climate records and thus the ice itself is a primary objective. Ice coring requires an anti-freeze drilling fluid. Consequently, the use of existing coring systems for access to subglacial environments may be limited. However, the borehole can be used for sample retrieval if certain precautions are taken. Thermo-probes are another means to access lakes. The probe uses a heated element at its head, melting ice as it moves down the ice column. The trailing water refreezes behind the probe. A tether is unwound from the probe as it descends. Information and power can be transmitted via the cable. Once in the lake, the probe can deploy instruments. Existing thermo-probes are generally designed for a one-way trip with no contingency for sample retrieval. However, it can be envisioned that new designs could plan for sample retrieval and return using thermal methods. The major problem with thermoprobes is that they can become ineffective if the ice contains particulate impurities. Even small amounts of particles tend to accumulate in the borehole as it deepens since fluids are not circulated away from the probe. This build-up of solids tends to retard the melting process and can cause the probe to stop or veer off course.
Hot water drilling can be used to reach the base of ice masses. Hot water drills typically use high-powered jets of water focused downwards into the ice. Narrow (<10 cm) hot-water holes can be quickly drilled through several kilometers of ice. Wider holes require several tens of hours to complete and consume significant quantities of fuel to avoid hole closure. A hot water drill has not yet penetrated the ice thickness that will be encountered in reaching most subglacial environments.
Related topics:
Enabling Technologies, Remote Observations, Models, ..... , In Situ Observations, and Sediment Cores