East Antarctica hosts the largest ice sheet on Earth, containing enough water to raise global sea levels by 52 metres, were it to fully melt. Yet it has puzzled scientists for decades how and why this ice sheet formed.

In fact, there are two interlinked mysteries. First, Antarctica became covered in ice around 34 million years ago – a period known as the Eocene-Oligocene transition – while the Arctic region stayed largely ice-free for another 25 million years or so.

Carbon dioxide levels in the atmosphere were falling dramatically at the time, and played an important role in falling temperatures. But if that was the sole factor behind the transition, both poles should have cooled together. They didn’t.

This means that something else was probably giving Antarctica a head start.

The second mystery is that sea-surface temperatures in the Southern Ocean remained unexpectedly warm for 10 million years or so after the East Antarctic Ice Sheet formed. This is not what we’d expect to see if the ice sheet had formed purely in response to global cooling, in which case the surrounding oceans should have cooled considerably too.

My new study with colleagues based in the UK and Germany, published in Science, points to an answer buried deep below the ice sheets: Antarctica’s mountains, and the slow motion geological forces that built them.

A continent on the move

This story begins around 170 million years ago, when Antarctica and Africa were last joined together as part of the supercontinent Gondwana. Their split sent Antarctica on a trajectory toward the South Pole – and........

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