An ice core which contains samples of Earth’s atmosphere from five million years ago has been pulled up from the continent’s Ong Valley, researchers have said.
When researchers drill and pull ice cores in Antarctica, they often hope to study the air bubbles that have been trapped in the ice, some of which go back millions of years, to learn more about the Earth's atmosphere.
Until now, most such core samples have been pulled from sites in eastern parts of Antarctica because the ice there has been deposited slowly in clean layers over millions of years.
For the new study, the researchers chose to drill instead in the Ong Valley, located in the Transantarctic Mountains, which, as their name suggests, separate eastern and western Antarctica.
Ice in the Ong valley was deposited there by glaciers that slid down from the mountains.
As the ice on top melted, rocks pulled down from the mountains created a layer of rock that protects the ice beneath it.
Prior research has suggested that the ice underneath could be from as far back as 5 million years ago.
The researchers drilled through the ice over the summers of 2017 and 2018, and were able to access the protected ice beneath the rock and to pull a core sample 9.5 meters long.
Initial testing of the isotopes it contained suggest the age of the ice ranges from 3 million to just over 5 million years.
Watch: These Rediscovered Ice Cores Could Help Predict Earth's Future Climate
Isotopes such as neon, aluminum and beryllium can be used for age testing because they were created by cosmic rays colliding with the rocks above.
The researchers also found that the ice sheet below the rocks actually comprises two sheets, one above the other, suggesting two glaciers wound up at that site in the valley, millions of years apart.
A sculpture with a capsule of glass containing Antarctic air from 1765 was shown off in Glasgow last year to highlight the damage wrought by the Industrial Revolution.
Artist and sculptor Wayne Binitie spent five years working with scientists from the British Antarctic Survey (BAS). reclaiming bubbles of air from ice cores from the Antarctic.
The air shows how the level of carbon dioxide in the atmosphere has changed since the Industrial Revolution began.
The year 1765 is considered a pivotal point: James Watt made efficiency improvements to the steam engine, helping to drive the industrial revolution.
Binitie said, “The scale of the topic is so overwhelming and so complex that it can feel distant, even apocalyptic.
“People need something tangible to get hold of, that collapses that distance.”
Dr. Robert Mulvaney from the BAS says, “Snow falls in Antarctica year by year – but there’s no melting going on.
“So the snow builds up and compresses all the years of snow beneath. As we drill down we’re driving further and further into the past – a bit like counting the rings of a big tree.”
Dr Mulvaney said ice core analysis shows that in around 1765, the atmosphere was 280 parts of carbon dioxide per million, which had been pretty constant for about 10,000 years.
The average in the atmosphere in May last year was 419 parts per million.