DISC Drill Breaks Record at WAIS Divide
Developed by engineers of the UW-Madison Space Science and Engineering Center Ice Drilling Design and Operations (IDDO) group, the Deep Ice Sheet Coring (DISC) drill has passed the previous record depth for US ice drilling. On 28 January 2011 the drill reached a depth of 3331 meters (10,928 feet), breaking the previous record of 3053 meters set in 1993 in Greenland.
The drilling and core handling crews celebrate record-breaking effort. Photo: Mark Twickler
The DISC drill is a “tethered” electro-mechanical drill that consists of a 16-meter down-hole portion (sonde) raised and lowered in the fluid-filled borehole by a winch via a cable approximately 15 mm in diameter.
The DISC Drill sonde
The sonde consists of six distinct and separable sections:
- the cutter head assembly that actually cuts the ice,
- the core barrel in which up to 4 meters of core is collected,
- the screen section in which chips of ice resulting from the cutting operation are separated from the drilling fluid and stored,
- the motor/pump section that houses a pump to circulate the drilling fluid and motors to drive the pump and rotate the lower portions of the drill that cut the ice,
- the instrumentation section that contains controls for the pump and cutting motors as well as numerous sensors to monitor the drilling operation, and
- the upper section that provides for the termination of the cable and “anti-torques” that center the drill and provide a torque reaction point to prevent the entire sonde from rotating.
The cutter head, core barrel and screen section rotate while the sections above are restrained.
Cross-section of DISC Drill cable
The cable used at WAIS Divide is 3800 meters long and has multiple functions. First, it provides the support for lowering and raising the sonde. Second, the cable provides the electrical conductors to transmit power from the surface to the motors and instruments in the sonde. Finally, the cable houses optical fibers through which data are sent between the sonde and the surface control system. The cable winch is electrically driven and is designed to have the smallest “footprint” possible.
As the borehole becomes deeper, a substantial amount of time is required to raise and lower the sonde. Consequently, ICDS engineers designed the winch to be operated at the fastest practical speeds. The DISC drill winch is capable of raising the sonde at a speed of 3 meters per second.
“The DISC drill is revolutionary technology,” said Alexander Shturmakov, director of engineering and research for IDDO. “Its electronic brain makes this drill more complex than any comparable device.”
Ice cores collected by the DISC Drill play an important role in the study of the history of Earth’s climate. By analyzing the gases, dust, ash, and other substances trapped in the layers of ice formed from annual snowfall in the Earth’s cold regions such as Greenland and Antarctica, scientists can reconstruct Earth’s climate thousands of years into the past. At the 3,300 meter mark, the ice (and the air trapped within it) is approximately 100,000 years old.
The ice cores produced by the DISC drill are 12.2 cm (4.8 inches) in diameter and up to three and one-half meters long. Deep inside the glacier, the pressure of the incredible weight of the overlying ice pushes on the borehole at all times, threatening to collapse it and trap the drill. Consequently, the shaft is filled with a fluid which provides the hydrostatic compensation necessary to prevent closure.
“Think of these cores as a giant library of ancient weather reports,” said Principle Investigator and Professor Emeritus Charles Bentley. “The scientific community decided what they needed for a new drill. They wanted lots of new capabilities. Their requests drove our design team and the result was the DISC drill.”
Professor emeritus Charles Bentley inspects the barrel of the Blue Ice Drill, another drill designed and built by the UW-Madison IDDO team.
The core is carefully preserved until it gets back to a laboratory in the US, where the ice is crushed in a vacuum to release the bubbles from their icy stasis. That yields a sample of air that was fresh tens of thousands of years ago. Climatologists can study the chemical composition of the atmosphere that existed during and before the last Ice Age.
The location of the WAIS Divide drilling site.
The most significant characteristic of the West Antarctic Ice Sheet (WAIS) Divide project is the development of climate records with an absolute, annual-layer-counted chronology for the most recent 40,000 years. Lower temporal resolution records will extend back for approximately 100,000 years.
These records will enable comparison of environmental conditions between the northern and southern hemispheres, and the study of greenhouse gas concentrations in the ancient atmosphere, with a greater level of detail than previously possible. While similar projects have collected data from Arctic ice in Greenland, the WAIS project is the first Southern Hemisphere project to gather climate records of comparable time resolution and duration.
At 3331 meters, the drill designed and built at the UW-Madison set the new US record as the deepest US ice core drilled.