Antarctica is a viciously inhospitable land, averaging a balmy -56C in the continent's interior. That's precisely where an intrepid band of American scientists have dug clean through 3405 metres of ice in an effort to research an aeon's worth of climate change. To do it, they used this one-of-a-kind coring machine.
The West Antarctic Ice Sheet (WAIS) Divide is a unique area in the Southernmost continent. Located in the southwest corner of Antarctica, it's akin to the North American divide in that it marks the boundary on the ice sheet where the two halves begin sloping in opposite directions. The snow along this divide therefore moves very little, which makes it ideal for a core sample to yield accurate, ancient data.
"The site was selected because it is the best place in the world to get a high-time resolution record of greenhouse gases that extends back about 40,000 years. It also is the best place in Antarctica to get a climate record to compare to the climate record from the Greenland ice cores," Ken Taylor, WAIS Divide chief scientist with the Desert Research Institute in Nevada, explained to the Antarctic Sun. "We wanted to get that high-time resolution so we could compare it to the Greenland ice cores. We also wanted a high-time resolution so that we could understand the influence that changes in greenhouse gases have on changing the climate."
Funded by the National Science Foundation and run by the United States Antarctic Program, the The WAIS Divide deep drilling project aims to bore a hole to the base of the WAIS ice sheet. Then, scientists will extract a single 3400m core that will provide an unprecedented look at how the Earth's climate has changed in the last 100,000 years.
To perform such a feat, the WAIS Divide team had to design and build a custom coring machine — no existing technology could be adapted to the harsh environment and exacting scientific specifications. So, in 2002, a team of engineers and technicians from the University of Wisconsin-Madison built the Deep Ice Sheet Coring (DISC) drill, a unique machine capable of cutting and extracting 122mm wide cores from the 4000m deep bowls of an ice sheet.
The drill assembly includes a sonde, cable, tower and winch. The sonde is the 2.7m long cutting head, consisting of four rotating bits that act to shave a solid core from the surrounding sheet. This is lowered into the shaft via the 15mm thick cable, where it cuts out an 2.4m long core, 12.2cm wide. When the sonde is retracted, it breaks the core off at its base and pulls it back up the shaft, where it is extracted from the machine. From there, the cores are packed and shipped quickly to the NICL's main archive freezer in Denver, Colorado, a massive 5100sqm cold locker that never warms above -36C.
It took five years of drilling (in 45-day stretches during the Antarctic winter) to reach the record-setting mark of 3405 metres. The previous deepest US bore was a Greenland plunge of 3053 metres, on July 1, 1993. "Not only is this the deepest ice core ever drilled by the US, but the fact that we have reached our target depth for this season means that the project is... on schedule," said Julie Palais, program manager for Antarctic Glaciology in the National Science Foundation's Office of Polar Programs. The overall deep drilling record, however — a 3701m bore at the eastern Antarctica Vostok Station — belongs to Russia.