Deep-Earth Forces Helped Antarctica Freeze Millions of Years Before the Arctic

Scientists have found a new explanation for why Antarctica became covered in ice millions of years before the Arctic did. The international study, published in the journal Science, addresses a long-standing puzzle: how Antarctica built a massive ice sheet at a time when Earth was about 5°C warmer than today.

The research, led by the University of Southampton with Durham University, Germany's GFZ Helmholtz Centre for Geosciences and the University of Potsdam, Utrecht University in the Netherlands, and the University of Florence in Italy, points to gradual uplift in East Antarctica. After Antarctica and Africa began separating during the Jurassic Period, 201-143 million years ago, slow-moving deep-Earth forces called "mantle waves" lifted an escarpment, plateau and mountain system over more than 100 million years, raising much of East Antarctica to colder elevations.

Computer models reconstructing 100 million years of surface change show that by about 45 million years ago, large parts of East Antarctica, including the Gamburtsev Mountains, had risen above roughly 2 kilometres — the elevation needed for mountain glaciers to persist year-round. Those glaciers merged into the East Antarctic Ice Sheet by around 34 million years ago. The ice sheet, now the largest on Earth, holds enough frozen water to raise global sea levels by about 52 metres if it melted completely.

Lead author Professor Thomas Gernon of the University of Southampton said falling carbon dioxide levels alone would have cooled both poles evenly; instead, Antarctica's uplift gave it a head start, since air temperature falls by about 1°C for every 100 metres of altitude gained, as co-author Dr. Guy Paxman of Durham University noted. Once ice began covering the continent, its bright surface reflected more sunlight back to space — an "ice-albedo effect" the researchers estimate cooled global temperatures by about 1°C, while the resulting drier air held less heat-trapping water vapour, reinforcing the cooling as ice spread from the mountains to the coast.