Rapid drilling to find ancient ice

Ice cores take a long time to collect. The 3.4 km- ice core drilled at Dome Concordia (Antarctica) took 5 years to collect and encloses the oldest ice drilled so far, reaching 800,000 years. The thickness of the ice and geothermal energy at this site result in ice at the bottom that was found to be melting, erasing precious past climate and environmental information.

In order to help finding the most suitable site in Antarctica to retrieve an ice core reaching 1.5 Ma year-old without having to collect a full ice-core, a new drill (the Rapid Access Isotope Drill, or RAID) is being developed by BAS. Rather than collect a full ice-core this drill will chop up the ice and will allow collecting ice chippings. Analysis of stable water isotopes on these ice chippings will then be done in the BAS lab facilities to infer the age of the ice. Drilling with RAID will be significantly faster since:

• the winch can be geared to operate much faster because we will not collect a full ice core (typically 1.5m long section drilled at a time with a 10cm-diameter),
• the borehole diameter has been reduced and less material is removed which also allows reducing the power requirements,
• the core quality is not important which allows the cutters to be more aggressive.

These improvements allow 600 meters to be drilling in approximately 7 days, a depth which would take over 2 months to drill conventionally. The new drill also provides an access hole down which a temperature sensing cable can be deployed to obtain a temperature profile for the upper 600m of the ice. Ice sheet modellers will use the temperature profile and data from ice radars (aPRES and DELORES) to calculate whether the ice is melting at its base.

Although the RAID is designed to search for older ice it will also provide a lightweight drill (about 530 kg) to access up to 650m of ice that will be particularly useful for other applications currently under development ( e.g. Rapid access to bedrock for sampling rocks).

• To provide a rapid way to assess the potential of a site to find ice older than 1 million years.
• To quickly collect ice chippings from up to 650m deep.
• To provide a quick access borehole to depths of 650m.