Anthony Doesburg: Real-life journey to the centre of the earth

New Zealand drilling technologists collecting Antarctic rock samples are having to overcome unique challenges in the name of climate change research.

As if the polar chill isn't enough to contend with, drill crews and scientists also have to drill 1000m or more into the Earth's crust from a moving ice platform.

It's a unique problem. And at this stage, with drilling due to take place during the 2012-13 summer, they haven't yet worked out how to solve it.

It's not that they don't have experience in drilling on the frozen continent. Alex Pyne, a geologist at Victoria University's Antarctic Research Centre, has been making holes through the ice and into the ground beneath for 30 years.

"Most of my career has been involved in Antarctic research and polar drilling," says Pyne, whose most recent mission was Project Andrill, carried out on the McMurdo Ice Shelf in 2006-07.

The purpose of Andrill, and the forthcoming drilling programme whose planning Pyne is leading, is to collect rock core samples from which scientists can get an understanding of the comings and goings of the West Antarctic ice sheet over the past several million years.

Sediments and traces of organic matter in the samples tell them what the environment was like and computer modelling allows them to visualise how rapidly the ice sheet melts and refreezes.

Andrill's initial findings, published in the journal Nature in March, showed that if the Earth's temperature continues on its present upward trajectory, most of the West Antarctic ice sheet will melt, raising sea levels about 8m over 1000 years.

The next drilling site will be on the Ross Ice Shelf, closer to the West Antarctic ice sheet, and 155km from McMurdo Station, the main US Antarctic base. That distance means a temporary camp will have to be set up to house the three dozen or so drill crew, scientists and support personnel.

The main challenge isn't the isolation, but the fact that the drilling rig will be sitting on ice that is moving 2-3m a day. That will place unknown stresses on the drilling gear, which has to pass through about 300m of compressed snow and ice and 700m of frigid water before reaching the sea floor.

The displacement of the rig is one problem - it can be expected to move more than 100m during drilling - but water currents are another. Pyne is working with a Texas consultancy to calculate how much flexing the "sea riser" - the 150mm steel pipe encasing the drill bit - will have to withstand.

"When it's 1000m long it's very thin and very flexible - currents can bend it."

There are two possibilities for drilling to the target depth of about 1000m. One is to drill to about 500m, withdraw the drill pipe, move the rig across the ice until it's over the hole once again, then re-enter the hole with the help of a remote-controlled submersible. The other approach is to drill to about 500m, pull out with the rig remaining where it is, drill a second hole to 500m without collecting core samples, before resuming coring.

The engineering required differs depending on the drill strategy, Pyne says, since the rig used for Andrill is set up for continuous coring rather than drilling an open hole.

And then there's the small matter of the cold. With only a couple of months in which to collect cores, Pyne says drilling is a 24-hour operation that can't be interrupted every time the breeze blows.

"We have to design the drilling system and our way of operating so we can carry on when conditions aren't very good outside."

Shelter is provided by a shroud that encloses the drill rig. Living quarters consist of insulated shipping containers and tents. Pyne says the conditions take some getting used to.

"If you're smart, you're not fighting it, you're working with the environment. It's a significant issue, learning what you can expect to be able to do and what you shouldn't even think about trying to do."

When bad weather sets in, the cold can lead to mistakes and equipment failure.

"The idea is to avoid that in the first place, which means you might go inside and have a cup of coffee, or something like that, and wait a day till the storm passes ... you need to know to do that."

After decades of polar drilling Pyne is inured to the rigours of the life and sees it as a job like any other. Solving engineering problems such as those posed by the next drilling programme is the exciting part.

"It's good when we've got interesting challenges."

Anthony Doesburg is an Auckland technology journalist.