When East Antarctica began developing a permanent ice sheet 34 million years ago, the Arctic remained without large-scale ice for another 25 million years. This asymmetry puzzled scientists for decades. A study published in Science early this month shows the answer lies in deep geological processes that quietly reshaped the southern continent long before global temperatures fell far enough to freeze the north.
The uplift of East Antarctica started with the Jurassic breakup of the supercontinent Gondwana between 201 and 143 million years ago. Mantle dynamics following that rifting drove progressive elevation gains over more than 100 million years. By around 50 million years ago the landscape had risen enough for mountain glaciers to appear by 45 million years ago. Those higher elevations proved decisive when the Eocene-Oligocene transition arrived.
Elevation sets the threshold for ice
Air temperature drops by roughly 1°C for every 100 metres of elevation gained. Thomas Gernon, a member of the research team, put it plainly: "Elevation matters enormously for ice. Air temperature drops by roughly 1°C for every 100 metres of elevation gained, so even a modest additional uplift can tip a mountain range from losing its snow each summer to keeping it year round."
Global temperatures had already declined from about 30°C 50 million years ago to nearer 20°C when the first major Antarctic ice sheet formed. The new ice itself then amplified cooling through higher albedo and reduced atmospheric water vapour, lowering global temperatures by another 1°C. That extra chill sufficed for the elevated Antarctic interior but fell short for the lower-elevation landmasses around the Arctic.
The findings underscore how solid-Earth processes operating over tens to hundreds of millions of years preconditioned one pole for glaciation well before the other.
The East Antarctic Ice Sheet holds enough frozen water to raise global sea levels by 52 metres were it to melt completely. Sea surface temperatures in the Southern Ocean stayed relatively warm for some 10 million years after the initial ice-sheet formation, a detail that earlier models struggled to reconcile with rapid global cooling narratives. The new work integrates geophysical modelling of mantle flow, palaeo-elevation reconstructions and climate simulations. It demonstrates that tectonic inheritance, rather than atmospheric carbon dioxide decline alone, explains the starkly different glacial histories of the two poles.
Challenging simplified climate narratives
Many accounts of polar ice formation have emphasised short-term atmospheric drivers while paying less attention to the long-term geological template. This research restores balance by showing how ancient continental rifting set the stage for asymmetric responses to the same global cooling trend. The mantle-driven uplift created high plateaus and ranges, including the Gamburtsev Mountains, that crossed the critical elevation threshold for perennial snow even under conditions warmer than those later required in the north.