More than a century ago, explorers from several countries raced to reach the globe’s southernmost point, driven by fierce international rivalries. Now, a new race is under way in Antarctica, this time motivated by the need to understand one of the gravest threats facing humanity.
While other ancient climate records exist, only the ancient ice near the poles holds a perfect record of the atmosphere’s carbon dioxide levels and temperature.
The oldest continuously layered ice anywhere on the planet is believed to have been laid down around 2 million years ago, on a 3300-metre-high ice plateau in the East Antarctic. It is also thought likely that it holds the secret to why the world’s climate abruptly changed between 1.2 million and 800,000 years ago.
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Until that time, Earth had glacial periods – commonly known as ice ages – roughly every 41,000 years, but suddenly, around 1.2 million years ago, something forced the climate to radically shift. By around 800,000 years ago, the planet had moved to a pattern of 100,000-year glacial cycles. No one knows why this so-called mid-Pleistocene transition occurred, but understanding it is critical to modelling future climate change as greenhouse gases surge.
Separate teams from Australia, Europe, Japan and the US have all begun drilling ice cores that could hold the answer to this puzzle, while and a are exploring candidate sites and looking to drill in the coming years.
Currently in the lead is a European consortium called Beyond EPICA. In January, the project reached the bedrock under 2.8 kilometres of ice at a location called Little Dome C in the East Antarctic plateau. Some of the ice the team has retrieved is
The Australian team was also planning to begin drilling at Little Dome C this summer, until new radar data 50 kilometres from the European drill site at a location called Dome C North, or North Patch.
When those findings emerged, the Australians had already established their camp at Little Dome C, but hadn’t begun to drill. Moving to a new drill site isn’t done lightly in the Antarctic’s interior: temperatures in summer average -30°C and the weather is so inclement that the window for drilling is a mere month or two per year.
Still, the team re-established their camp and . The researchers managed to drill a 150-metre pilot bore and set up all the equipment needed to start deep drilling next summer. Team leader at the Australian Antarctic Program says it will probably take until the Antarctic summer of 2029 before they are able to drill through the remaining 3 kilometres of ice and reach bedrock.
From Casey station, the nearest permanent base, it is a mere 6-hour flight back to Hobart in Tasmania, so the Australian team has already brought its cores home and will start analysing them in the coming months. Meanwhile, unwilling to take the risk of transporting ancient cores through multiple customs-stops by air, the European team faces a nervous wait while its ice cores are transported to Italy by ship.
Team member at the Ca’ Foscari University of Venice in Italy says he is losing sleep worrying about all the possible mishaps that could damage the cores. Once they are safely in the laboratory at the end of April, it will take at least two months to prepare sections of the ice cores for study, he says.
“The first thing is to establish an age scale,” says Barbante. “So, we need to know how old the ice is. And then, in parallel, we’ll do analysis to reconstruct the temperature of the past.”
The researchers will study the isotopic composition of the water molecules, the chemistry and the gas composition held in the ice.
Complicating matters, the last couple of hundred metres of ice above the bedrock at Little Dome C is what researchers call “stagnant”. This means the stratification of the deepest ice has been destroyed by disturbances as the ice sheet has ground over the bedrock.
“For millions of years, you have disturbances in the bottom layer of the ice,” says Barbante. “Because we don’t see any more stratification, the oldest continuous ice record is not at the very bottom.”
Radar imaging at Dome C North, however, appears to show that there is no stagnant ice layer there, says Pedro. “We’re hoping that we preserve continuous stratified ice all the way to the bedrock.”
For Barbante and his team, analysing this ancient ice will be the best chance the world has of predicting the future by understanding the past. “It is a gigantic work in very, very harsh conditions and is a 20-year-long dream come true,” says Barbante. “This is a huge, huge programme, like a space mission.”
But he won’t be disappointed if the Australian team surpasses his own in the hunt for the oldest ice, he says. “If, in the coming years, our Australian colleagues touch ground and it will be 2 million years old, we will be super happy, as that is for science – it is not for a national or a personal record.”
