What lies beneath Antarctica’s icy blanket
Jamie Morton says Kiwi scientists are trying an unusual approach to explore under the ice mass
Kiwi scientists are trying an innovative approach to work out what’s 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 luckily 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 on the continent, 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.
And, more importantly, 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, Augustinus said.
While there was still much uncertainty around precisely how this would play out, he 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 . . . [understanding] ice sheet stability.”
What we know about the AIS base 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 DNAbased 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, the Kiwi team will set up a field camp 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 mix of mapping approaches to optimise the sampling of the different carbonatetypes 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.
“An improved understanding of hydrological conditions at the base of the AIS has implications beyond the Antarctic . . . [it] could even feed into models used to predict sealevel rise impacts on the New Zealand maritime zone — as well as changing climate.”
The five-strong team is being supported by Antarctica NZ.