Antarctic holds clues to future

Tim Naish

How much and how quickly will the ice shelves in Antarctica melt as the global warming noose tightens, and with what consequences?

These are the core questions that a New Zealand-led group of 50 scientists leaving for the icy continent tomorrow hopes to answer.

The team, co-led by GNS scientist Tim Naish, will use a Wellington-developed drill rig to tap into Antarctica's 100m-thick Ross Ice Shelf, to retrieve a 1000m-long core of sediment and rock from beneath the seabed.

"The reason is to find out how the ice sheets behaved in the past, and particularly during times when global temperatures - and Antarctic temperatures - were a few degrees more than they are today, times similar to where we're heading with global warming," Dr Naish said.

The team - part of the Andrill (Antarctic geological drilling) programme - expects the results to show the history of the ice from 5 million to 10 million years ago, and more detailed results for the past million years.

"We know there are some super-warm periods of global warmth - warmer than present - about 125,000, 250,000 and 400,000 years ago. We will drill to these periods and see some direct evidence of the Ross Ice Shelf collapsing or significantly retreating, and maybe even the West Antarctic ice sheet collapsing," he said.

"The idea is to understand how fast [it happened], the nature of the collapse and under what temperature conditions it happened."

Dr Naish said there was plenty of information on how climate change could affect the polar north, but no research about the polar south, a void the team aimed to fill.

Scientists predict global temperatures to rise between 1C and 6C by the end of the century, with disastrous consequences for even a 2C to 3C rise.

But even in a worst-case scenario, Dr Naish said, the effects would only be felt at a snail's pace.

"We expect it to be in the order of hundreds of years to thousands of years. Though it is starting to accelerate now, we still don't expect sea level to rise by more than a metre in the next century," he said.

Drilling at the shelf, 15km west of Scott Base, will last until the end of December, with initial results expected next year. The drill will pass through 100m of floating ice in McMurdo Sound, then through 900m of water and into 1000m of sediment and rock.

Samples will go to the US-run McMurdo Station for analysis. A second drill site, 25km east of Scott Base, is planned for summer 2007-08.


The drill

* The Antarctic drilling project will have to bore through 100m of ice before it can begin drilling into the seabed 1km below the ice to recover a 1km core.

* The core will reveal climatic events stretching back 400,000 years.