What lies beneath Antarctica's ice?

A team led by the University of Auckland's Associate Professor Paul Augustinus is attempting a novel way to discover what lies beneath the vast Antarctic Ice Sheet. Photo / Supplied

Kiwi scientists are using an innovative approach to try to work out what's happening beneath part of the largest single mass of ice on Earth.

The Antarctic Ice Sheet (AIS) holds some 26.5 million cubic km of ice – and sprawls across 14 million sq km, or around 98 per cent of Antarctica itself.

The sheer size of the ice sheet makes it extremely hard for scientists to access and study what the conditions are like underneath it.

But, fortunately, there are some small, ice-free areas around the Antarctic margin where they sometimes find unusual deposits created by meltwater at the ice sheet base.

A team of researchers currently on the continent, and led by the University of Auckland's Associate Professor Paul Augustinus, are turning to cutting-edge instruments including drones and laser scanners to work out how this material formed.

More importantly, he said, it could tell us about changing nature of – and the causes and location of - meltwater beneath the vast sheet.

The contribution of the world's ice sheets to global sea level rise – and Antarctica holds an equivalent 60m - would likely increase in the future, he said.

While there was still much uncertainty around precisely how this would play out, Augustinus said rapid changes in water at the base of ice sheets was a potential additional driver of ice sheet response to changing climate and sea-level rise.

"More than 400 subglacial lakes exist under the AIS with the exchange of water between them sometimes involving catastrophic discharges," Augustinus said.

"The implication is that much of the AIS has basal meltwater - with important implications for a complete understanding of ice sheet stability."

What we know about the nature of the base of the AIS is largely limited to geophysical studies and glaciological modelling, with actual observations limited to the few ice cores that penetrate to the ice sheet base.

But we could solve some of the puzzle by developing unique records of past sub-glacial hydrological conditions using calcium carbonate – or calcite and aragonite – formed from meltwater at the ice sheet base of the AIS from Northern Victoria Land and other ice-free areas.

"These deposits contain geochemical and microbial DNA-based evidence of the nature and mode of formation of the meltwater, that curiously also contain signals of volcanically-heated meltwater," Augustinus said.

"Interestingly, some of the bacterial DNA preserved in the deposits are more akin to what we might find in hot springs in New Zealand."

After flying to Northern Victoria Land's Helliwell Hills, Augustinus and his team will set up a field camp on a previously-used site overlooking Boggs Valley.

"Our project largely involves detailed mapping of the unusual carbonate deposits precipitated at the base of thick ice – as well as the associated glacial landforms," he said.

"We are using a range of technologies to do the mapping: drones, GPS, terrestrial laser scanners with all the data and images integrated into an ArcGIS database."

They'd use this combination of mapping approaches to optimise the sampling of the different carbonate-types they found in the field.

"Our work will improve our understanding of the nature, timing and drivers of changing hydrological conditions under the Antarctic Ice Sheet using these deposits that have formed over the past 340,000 years," he said.

"This new knowledge will hopefully contribute to improved prediction of AIS response to a warming world.

"An improved understanding of hydrological conditions at the base of the AIS has implications beyond the Antarctic continent whereby this information could even feed into models used to predict sea-level rise impacts on the New Zealand maritime zone - as well as changing climate."

The five-strong team is being supported by Antarctica New Zealand.