Climate change: Will this vast Antarctic ice sheet reach tipping point?

Scientists are to retrieve samples from below Antarctica's Ross Ice Shelf, to learn how ice responded when global temperatures were as warm as those expected in coming decades. Photo / Neil Silverwood

Kiwi scientists are preparing to drill deep into the Antarctic ocean floor, to reveal whether a vast ice sheet storing several metres of equivalent sea level rise is at risk of reaching tipping point.

As world leaders meet at a major UN climate change summit in Glasgow, an international team are about to retrieve ancient sediments from below Antarctica's Ross Ice Shelf, to find out how ice behaved when global temperatures were as warm as those expected in the coming decades.

These geological records could tell us whether there's a threshold in our climate system when large amounts of land-based ice melts, causing oceans to rise many metres — if it has happened before, it could happen again.

Ultimately, the team aims to test the sensitivity of the West Antarctic Ice Sheet – storing enough ice to push up global sea levels by 4m – to 2C of global warming.

Earlier this year, scientists warned that, unless there were immediate, rapid and large-scale emissions reductions, limiting warming to close to 1.5C - or even 2C – would prove beyond reach.

The 1.5C threshold – the focus of upgraded Paris Agreement pledges being tabled by nations in Glasgow – could be crossed within just 11 years at current global emission rates.

Later this month, a preparation team will head out from New Zealand's Scott Base to complete a 1200km-long traverse of the Ross Ice Shelf to the Siple Coast, where land ice meets the ocean and starts to float.

Once the drilling camp has been established, the wider science team will join the group and work through Antarctica's summer until February.

No one has ever drilled into the Antarctic seabed at a location so far from a major base, or so close to the centre of the West Antarctic Ice Sheet.

"We have formed a team of drillers, engineers, field experts and scientists who are up to the task," said GNS Science and Victoria University paleoclimatologist Dr Richard Levy, who is co-leading the effort with US colleague Dr Molly Patterson.

"Discoveries will show us how much the West Antarctic Ice Sheet could melt if we miss Paris Agreement targets."

Engineers at Victoria University's Antarctic Research Centre (ARC) have already spent four years developing world-first technology capable of hot water drilling through around 800m of ice before taking sediment samples from up to 200m beneath the ice sheet.

Patterson, of Binghamton University in New York, said geological data provides direct evidence on the extent of the ice during a given time period.

"This information is necessary to assess whether climate models are able to capture observed variability during warmer times in Earth's history prior to making any assumptions about the future."

ARC director Associate Professor Rob McKay described the programme - dubbed Sensitivity of the West Antarctic Ice Sheet in a warmer world, or SWAIS 2C - as a massively ambitious undertaking.

Around $6.4m has been contributed by New Zealand, the United States, Germany, Australia, the United Kingdom and the Republic of Korea, with several other nations planning to join.

This map shows drill sites where the team will retrieve sediments from the ocean floor beneath the Ross Ice Shelf - and the route of a 1200km traverse from Scott Base. Image / GNS Science

The International Continental Scientific Drilling Programme awarded the project a $1.6m grant – a first for an Antarctic drilling project.

"The fact that so many countries are joining us in this effort highlights the urgency to understand more about the West Antarctic Ice Sheet, which remains the largest uncertainty for sea-level rise projections," McKay said.

The West Antarctic Ice Sheet is considered vulnerable to climate change because much of its ice, which rests on bedrock thousands of metres below sea level, is exposed to the warming Southern Ocean.

Antarctic Science Platform programme leader Professor Tim Naish saw understanding the ice sheet's potential fate as intertwined with global climate negotiations.

"Did the West Antarctic Ice Sheet collapse the last time the Earth warmed?" he said.

"Can we save the Antarctic Ice Sheet if nations meet the Paris Agreement targets?"

Antarctica New Zealand's chief scientific adviser, Professor John Cottle meanwhile considered the programme an exciting development for Antarctic climate science – and our important part in it.

"International recognition and support for the SWAIS 2C project highlights New Zealand's world leadership in scientific drilling in Antarctica," he said.

"The climate records retrieved in this project will be critical to a much better understanding of how Antarctica will respond to a warming planet."