For a long time, the story seemed straightforward. As atmospheric carbon dioxide levels fell and the planet cooled, large ice sheets began spreading across the polar regions. Yet there was an awkward detail that never quite fitted. Antarctica became locked beneath vast quantities of ice around 34 million years ago, while the Arctic remained largely ice-free for tens of millions of years afterwards. If global cooling was the main trigger, why did the two poles respond so differently. A study published in Science, titled “Continental breakup–driven uplift instigated East Antarctic Ice Sheet formation”, now points towards an answer buried deep beneath Antarctica itself. Rather than climate acting alone, the researchers argue that changes in the continent’s landscape, driven by geological events that began more than 100 million years earlier, helped create the conditions needed for permanent ice to gain a foothold. Antarctica’s elevation may have mattered just as much as the cooling atmosphere.
Why Antarctica froze millions of years before the Arctic
The northern polar region faced a very different situation. Reuters notes that glaciers appeared and disappeared across northern high latitudes over millions of years, but stable continental-scale ice sheets did not emerge until much later. Geography helps explain why.Unlike Antarctica, the North Pole sits in the middle of an ocean rather than atop a continent. There was no large landmass positioned directly at the pole that could be gradually lifted above a snow-retaining elevation threshold. Without extensive high ground, colder global conditions were needed before permanent ice could establish itself. Antarctica effectively received a geological head start. Its elevated interior allowed ice sheets to develop while the world was still comparatively warm. Northern Hemisphere glaciation required additional cooling because much of the available terrain remained at lower elevations. That difference helps explain one of the most persistent mysteries in Earth’s climate history: why the South Pole entered the age of large ice sheets roughly 20 to 25 million years before the North Pole followed suit.Rather than being a simple consequence of falling carbon dioxide, the timing appears to have been shaped by a long interaction between deep-Earth processes, mountain building and climate. Antarctica’s ice, it seems, began forming long before the Arctic’s because the continent itself had been quietly rising towards the necessary conditions for millions of years.
How the breakup of Gondwana reshaped Antarctica’s future
The roots of the story stretch back to the breakup of Gondwana, the ancient supercontinent that once united Antarctica with Africa, South America, Australia and the Indian subcontinent. When Africa began separating from Antarctica during the Jurassic period, the process did not simply alter coastlines. Deep within the Earth, disturbances travelled through the mantle. The Science study describes these disturbances as long-lived mantle waves that gradually migrated beneath the continent over tens of millions of years.As these waves moved inland, they altered the density structure beneath Antarctica. Material was stripped away from the underside of the continental crust, making sections of the landmass more buoyant. Over immense spans of time, parts of eastern Antarctica slowly rose.The researchers reconstructed these changes using landscape evolution models combined with ice-sheet and climate simulations. Their results indicate that uplift spread far inland from Antarctica’s ancient margins, eventually rejuvenating the Gamburtsev Mountains, a mountain range now buried beneath kilometres of ice in the continent’s interior.As per the study, the process began with continental separation more than 160 million years ago but continued influencing Antarctica’s surface long afterwards. Reuters reported that the uplift ultimately produced terrain high enough to favour permanent ice formation long before similar conditions existed in the Arctic.
Origins of Antarctica’s ice sheets and the South Pole’s frozen landscape
The Antarctica familiar today is a world of ice deserts, towering glaciers and temperatures that can plunge below -80°C. Earlier in Earth’s history, it looked very different.During the Eocene, between roughly 56 and 34 million years ago, Antarctica supported forests and experienced a considerably milder climate. Global temperatures were warmer than they are today, and sea surface temperatures around the continent were far from the frozen conditions now associated with the Southern Ocean.Yet somewhere near the boundary between the Eocene and Oligocene epochs, a dramatic transformation began. Ice sheets expanded across East Antarctica and eventually merged into the enormous ice mass that still dominates the continent. The puzzle was that this happened while parts of the world remained relatively warm. Research suggests the answer cannot be explained by atmospheric carbon dioxide alone. Instead, Antarctica appears to have been unusually well prepared for glaciation because its landscape had already been reshaped over millions of years.
How Antarctica’s rising mountains created ideal conditions for ice sheets
Mountain environments behave differently from low-lying landscapes. Air cools with altitude, allowing snow to survive for longer periods and increasing the chances of year-round ice accumulation.According to the study, eastern Antarctica gradually crossed a critical threshold. By around 45 million years ago, expanding uplands and rejuvenated mountain ranges had lifted large areas above elevations favourable for sustaining permanent snow and ice. As those high regions grew, so did the potential for glaciers to develop and persist.The researchers estimate that by the time major glaciation began roughly 34 million years ago, nearly 90 per cent of the Gamburtsev region lay above the elevation needed to support enduring ice. Earlier in the continent’s history, only a much smaller proportion of the landscape occupied that climatic zone.Their modelling suggests this topographic evolution helped ice caps expand even though global temperatures remained warmer than modern values. Once ice began spreading, its reflective surface increased the amount of sunlight bounced back into space, reinforcing cooling and encouraging further ice growth.In this view, Antarctica was not merely responding to climate change. The continent’s rising landscape was actively shaping how climate translated into ice-sheet formation.
