Planes and satellites are used to conduct surveys of the features that lie below the Antarctic Ice Sheet. Photo: ICECAP
By Jack Ryan of ABC
From high above, the icy kingdom of Antarctica appears as a vast, flat wilderness. A white sheet, draped over the planet's southern pole.
But beneath the ice lies a surprising and mysterious landscape, hidden from sight since the continent began to freeze over some 34 million years ago.
Over the past several decades, scientists have begun to map this subsurface realm, attempting to uncover the unseen canyons, peaks and valleys that shape Antarctica.
A new study, published in the journal Nature Communications ,has examined a corner of this underworld in great detail for the first time, revealing a landscape of deep valleys and high mountain peaks.
The region, covering about 32,000 square kilometres and lying around 2km below the East Antarctic Ice Sheet, is known as Highland A.
It was first discovered in 2011 but Stewart Jamieson, a geographer from Durham University in the UK who co-led the latest research, said his team wanted to look at the features in more detail.
A plane flies over the surface of Antarctica to conduct a survey of the region Photo: ICECAP
"We've returned to look at these because our community is realising that we don't just need to know the large-scale features, but we also need to understand the more detailed features too because these tell us about the past behaviour of the ice sheet," Jamieson said.
The find provides a glimpse of how Antarctica's vast ice sheets might change - or resist change - as the planet warms.
Looking below the Antarctic ice sheet
Using satellite data, the team homed in on Highland A, mapping changes in elevation at the surface and below by using radar imaging.
The data reveals the area contains "three distinct landscape blocks", ranging between 121km long (about the distance between Melbourne and Ballarat) to 173km long.
Illustration showing Antarctica with the ice sheet lifted from the continent. Photo: Stewart Jamieson / Durham University
In between the blocks are the two large and deep valleys, which previous research has shown were likely fjords - V-shaped troughs carved into the earth by glaciers.
Jamieson and colleagues suggest these features may have been created by a river network that existed during the Cretaceous period, a time up until 66 million years ago when dinosaurs still roamed the Earth.
As landmasses began to shift, the rivers likely flowed until some time between 34 million and 14 million years ago, when the area began to freeze.
Then, as the continental ice sheet expanded across the region during that period, Highland A was gradually buried under kilometres of ice.
The landscape was frozen in time and has remained largely unchanged since.
"This little corner of Antarctica has not evolved significantly for a very long time and this can therefore be used as a way to control computer models of ice sheet change," Jamieson said.
The stability of Highland A is particularly useful to understand past climates.
As the region appears to be mostly unchanged, it's unlikely this area melted away during warm periods over the past 14 million years.
During that time, Earth experienced the Miocene period, where temperatures may have been up to 7C warmer than today.
"It is remarkable that this landscape, 'hidden in plain sight' for many years, can tell us so much about the early, and long-term, history of the East Antarctic Ice Sheet," noted Neil Ross, a polar scientist at Newcastle University and co-author of the study, in a press release.
What can the ice tell us?
The East Antarctic Ice Sheet locks away a huge amount of the planet's fresh water.
As the planet warms, due to human-induced climate change, the ice sheet will begin to change.
The landscape beneath the sheet is crucial; it controls how ice flows and determines how it might respond to future thawing or melting.
Jamieson said if all the ice in East Antarctica melted, then seas could rise by approximately 53 metres.
Such an apocalyptic scenario would take a few hundred years to come to fruition, but as the ice slowly melts, what might we expect to see? How much ice will be lost?
Earth's near future could reflect some of the same climatic conditions not seen for millions of years if we continue to burn fossil fuels at the current rate.
Satellite image of the ice surface from Radarsat with the valleys and ridges of the buried ancient mountains mapped. Photo: Stewart Jamieson / Durham University
In some regions, like Highland A, warmer temperatures might not disturb the ice sheet dramatically.
But in other regions, we might see extreme retreat or total collapse, Jamieson said.
"It is understanding these differences which will help us understand how the ice sheet will respond to future climate change," he said.
Highland A also hints that Antarctica hides a bounty of surprising and important subsurface features.
Jamieson said while we broadly know where the big mountain ranges and lakes exist below the ice, there were still significant gaps in our understanding of what lies beneath.
That does not mean he is necessarily done with Highland A, though.
"It would be a fascinating place to go and drill through the ice and sample the bedrock - this would help confirm our mapping and to understand the age of the landscape," he said.
- This story was first published on the ABC.
