For a long time, the story seemed clear. As carbon dioxide levels in the atmosphere fell and the planet cooled, large ice sheets began to spread across the polar regions. However, there were strange details that didn’t quite fit.
Antarctica became trapped under massive amounts of ice about 34 million years ago, while the Arctic remained largely ice-free for tens of millions of years after that. If global cooling was the main trigger, why were the poles responding so differently? A study published in the journal Science, titled “Continental uplift leads to formation of the East Antarctic Ice Sheet,” suggests 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 ago, helped create the conditions necessary for permafrost to gain a foothold.
The height of Antarctica may have been as important as the cold atmosphere.
Why did Antarctica freeze over millions of years before the North Pole?
The Arctic faced a completely different situation. Reuters points out that glaciers appeared and disappeared across high northern latitudes over millions of years, but stable ice sheets at the continental level did not appear until much later. Geography helps explain why.Unlike Antarctica, the North Pole is located in the middle of the ocean and not above a continent.
There was no large landmass placed directly at the pole that could be gradually raised above an elevation threshold that would maintain snow. Without extensive high ground, cooler global conditions were needed before permafrost could establish itself. Antarctica effectively got a geological head start. Its high interior allowed ice sheets to develop while the world was still relatively warm.
Glaciation in the Northern Hemisphere required additional cooling because much of the available terrain remained at low elevations.
This difference helps explain one of the most pressing mysteries in Earth’s climate history: why the Antarctic entered an era of large ice sheets approximately 20 to 25 million years ago before the Arctic followed suit.Rather than being a simple result of declining carbon dioxide, the timing appears to have been shaped by a long interaction between deep-Earth processes, mountain formation, and climate. It appears that the ice in Antarctica began forming long before the ice in the Arctic, because the continent itself had been quietly rising toward the necessary conditions for millions of years.
How the breakup of Gondwana reshaped the future of Antarctica
The story’s roots go 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 to separate from Antarctica during the Jurassic Period, this process not only changed coastlines. Deep within the Earth, disturbances traveled through the mantle. The Science study describes these disturbances as long-lasting mantle waves that gradually migrated beneath the continent over tens of millions of years.As these waves traveled inland, they changed the density structure beneath Antarctica. Material has been stripped from the underside of the continental crust, making parts of the land mass more buoyant. Over huge periods of time, parts of East Antarctica slowly rose.The researchers reconstructed these changes using landscape evolution models combined with ice cover and climate simulations. Their results suggest that uplift spread far beyond the ancient boundaries of Antarctica, eventually leading to the rejuvenation of the Gamburtsev Mountains, a mountain range now buried under kilometers of ice in the interior of the continent.According to the study, the process began with continental separation more than 160 million years ago, but continued to affect the surface of Antarctica long after that. The uplift eventually produced terrain high enough for permafrost to form long before similar conditions existed in the Arctic, Reuters reported.
The origins of Antarctica’s ice sheets and the frozen landscape of Antarctica
The Antarctica we are familiar with today is a world of icy deserts, towering glaciers and temperatures that can drop below -80 degrees Celsius.
Earlier in Earth’s history, things looked very different.During the Eocene Epoch, approximately 56 to 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 across the continent were far from the freezing conditions now associated with the Southern Ocean.However, somewhere near the border between the Eocene and Oligocene, a radical transformation began.
Ice sheets expanded across East Antarctica and eventually merged into the massive ice mass that still dominates the continent. The puzzle was that this happened while parts of the world remained relatively warm. Research suggests that the answer cannot be explained by atmospheric carbon dioxide alone. Instead, Antarctica appears to have been unusually prepared for glaciation because its landscape had already been reshaped over millions of years.
How Antarctica’s high mountains created ideal conditions for ice sheets
Mountain environments behave differently than lowland landscapes. The air cools with elevation, allowing snow to remain for longer periods and increasing the chances of ice accumulating throughout the year.According to the study, East Antarctica has gradually crossed a critical threshold. About 45 million years ago, the expansion of uplands and renewed mountain ranges raised large areas above elevations suitable for maintaining permanent snow and ice.
As these higher elevations grew, so did the potential for glaciers to develop and persist.Researchers estimate that by the time the Great Glaciation began about 34 million years ago, nearly 90% of the Gamburtsev region lay above the elevation needed to support permafrost. Earlier in the continent’s history, that climate zone occupied only a much smaller proportion of the landscape.Their models suggest that this topographic evolution aided the expansion of the ice caps even though global temperatures remained warmer than modern values. Once the ice began to spread, its reflective surface increased the amount of sunlight bouncing back into space, enhancing cooling and encouraging further ice growth.From this perspective, Antarctica was not just responding to climate change. The continent’s upwelling landscape was actively shaping how climate translated into the formation of ice sheets.