The East Antarctic Ice Sheet, which holds enough water to raise global sea levels by 52 metres, formed 34 million years ago due to a combination of falling carbon dioxide levels and localized geological uplift. Research published in Science by a team from the UK and Germany suggests that “mantle waves”—tectonic instabilities moving beneath the continent—pushed mountain ranges to elevations high enough to sustain permanent ice long before the rest of the planet reached the same cooling threshold.
How did Antarctica ice over before the rest of the world?
Scientists have long struggled to explain why Antarctica became glaciated 34 million years ago during the Eocene-Oligocene transition, while the Arctic remained ice-free for another 25 million years. While atmospheric carbon dioxide levels were dropping globally, that cooling alone was insufficient to trigger ice formation at both poles simultaneously. According to the study, Antarctica possessed a unique advantage: its internal topography was being reshaped by the Earth’s mantle.
As the supercontinent Gondwana broke apart 170 million years ago, hot material from the mantle began to well up and cool. This process created “mantle waves,” which traveled over 1,000 kilometres beneath Antarctica. These waves stripped away deep continental roots, causing the land surface to rise—much like a hot air balloon shedding ballast. This uplift reached the Gamburtsev mountains roughly 50 million years ago, pushing peaks above 2,000 metres and creating the necessary altitude for year-round snow accumulation.
Air temperature typically drops by 1°C for every 100 metres of elevation. By pushing the Gamburtsev range above 2km, the mantle-driven uplift created the “cold trap” necessary for the East Antarctic Ice Sheet to initiate.
Why did Southern Ocean temperatures remain warm?
One of the enduring mysteries of Antarctic climate history is why Southern Ocean surface temperatures remained unexpectedly warm for 10 million years after the ice sheet began to form. If the ice sheet were merely a response to global cooling, researchers would expect to see a corresponding drop in regional ocean temperatures. However, the study indicates that the ice sheet was a localized, elevation-driven phenomenon rather than a result of planetary-scale freezing.
The growth of the ice sheet triggered two critical feedback loops that eventually expanded the ice to the coast without immediately freezing the surrounding oceans:
- Albedo effect: The reflective surface of the ice and snow reduced solar absorption, cooling the immediate region by roughly 1°C.
- Water vapour reduction: Cooler air holds less water vapour, a potent greenhouse gas. This reduction weakened the atmospheric insulating blanket, facilitating further localized cooling.
These loops allowed the ice to grow from mountain highlands to the coast, while global northern hemisphere landmasses remained too low in elevation to initiate their own ice sheets until much later.
What does this tell us about the future of ice sheets?
Understanding the geological formation of the East Antarctic Ice Sheet provides a sobering perspective on modern climate change. According to the research, the conditions required to build a continental ice sheet are extraordinarily specific and require tens of millions of years of geological evolution. Conversely, the loss of this ice can occur at a much faster rate.
The study highlights that once these massive ice structures are lost, they cannot simply grow back under current conditions. The geological “stage” set by mantle-driven uplift over millions of years is not a reversible process on human timescales. This suggests that the current stability of the East Antarctic Ice Sheet is reliant on a fragile balance of elevation and climate that, once disrupted, may not be easily restored.
Frequently Asked Questions
Why didn’t the Arctic freeze at the same time as Antarctica?
The Arctic landmasses did not have the necessary elevation to cross the threshold for permanent glaciation 34 million years ago. It took another 25 million years of falling CO₂ levels and further global cooling for northern ice sheets to develop.
What are mantle waves?
Mantle waves are disturbances in the hot, sticky rock beneath a continent caused by the rifting of tectonic plates. These waves can strip away deep continental roots, causing the surface to uplift or triggering volcanic activity.
Is the East Antarctic Ice Sheet currently stable?
The study notes that while ice sheets take millions of years to form, they can disappear much faster. Because the conditions for their formation are so specific, their loss is considered a critical, long-term concern for global sea-level rise.
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