For a long time the story seemed simple. As atmospheric carbon dioxide levels dropped and the planet cooled, large sheets of ice began to spread across the polar regions. Yet there was one strange detail that never fit. Antarctica became locked under heavy ice about 34 million years ago, while the Arctic remained largely ice-free for millions of years thereafter. If global cooling was the main trigger, why did the two poles react so differently. A study published in Science, titled “Continental breakup-driven uplift drove the formation of the East Antarctic Ice Sheet”, now points to the north buried deep beneath Antarctica. The researchers argue that rather than simply influencing climate, changes to the continent’s landscape caused by geological events that began more than 100 million years ago helped create the conditions necessary for permanent ice to gain a foothold. The altitude of Antarctica may have mattered as much as the cold environment.
Why did Antarctica freeze millions of years before the Arctic?
The northern polar region faced a very different situation. Reuters says glaciers have appeared and disappeared in 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 is located in the middle of the ocean rather than over a continent. There was no large land mass directly at the pole that could be gradually raised above the altitude limit that maintained ice. Without extensive highlands, cold global conditions were required before permanent ice could be established. Antarctica effectively gained the geological edge. Its high interior allowed ice sheets to develop while the world was still comparatively warm. Northern Hemisphere glaciers required additional cooling because much of the available land mass was at low elevations. This 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 about 20 to 25 million years ago after the North Pole.Rather than being a simple result of falling carbon dioxide, the timing appears to have been shaped by a long interaction between deep-Earth processes, mountain formation, and climate. It seems that Antarctica’s ice began forming long before the Arctic because the continent itself had been quietly growing toward 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 the ancient supercontinent Gondwana, which once connected Antarctica with Africa, South America, Australia and the Indian subcontinent. When Africa began to separate from Antarctica during the Jurassic period, it was not just the coastlines that changed in the process. Deep within the Earth, the disturbance traveled through the mantle. Science studies have described these disturbances as long-lived mantle waves that slowly moved beneath the continent over millions of years.As these waves moved inland, they changed the density structure beneath Antarctica. Material was removed from beneath the continental crust, causing parts of the land to become more buoyant. Over vast periods of time, parts of East Antarctica gradually rose.The researchers reconstructed these changes using landscape evolution models combined with ice sheet and climate simulations. Their results indicate that uplift extended far inland from Antarctica’s ancient margins, ultimately rejuvenating the Gumbertsev Mountains, a mountain range now buried under several kilometers of ice in the continent’s interior.According to the study, this process began with continental separation 160 million years ago but continued to affect Antarctica’s surface long after. Reuters reported that the uplift eventually created enough high ground for permanent ice formation long before similar conditions existed in the Arctic.
The origin of Antarctica’s ice sheets and the frozen landscape of the South Pole
Antarctica today is familiar to the world of ice deserts, vast glaciers and temperatures falling below -80 degrees Celsius. Earlier in Earth’s history it looked very different.During the Eocene, about 56 to 34 million years ago, Antarctica was forested and experienced a fairly mild climate. Global temperatures were warmer than 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 change began. Ice sheets spread across eastern Antarctica and eventually merged into the vast ice mass that still dominates the continent. The puzzle was that this happened when some parts of the world remained relatively warm. Research shows that the answer cannot be explained by atmospheric carbon dioxide alone. Instead, it appears that Antarctica was 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. The air cools with altitude, allowing snow to last longer and increasing the likelihood of snow accumulation throughout the year.According to the study, East Antarctica gradually crossed a critical threshold. About 45 million years ago, upland expansion and resurgent mountain ranges raised large areas above elevations favorable for maintaining permanent ice and snow. As those highlands grew, so did the likelihood of glaciers developing and persisting.Researchers estimate that by the time major glaciation began about 34 million years ago, about 90 percent of the Gamburtsev area was above the elevation required to maintain permanent ice. Earlier in the continent’s history, only a very small portion of the landscape existed in that climate zone.Their modeling shows that this topographic growth helped expand the ice caps, even as global temperatures remained warmer than modern values. Once the ice began to spread, its reflective surface increased the amount of sunlight reflected back into space, increasing cooling and promoting further ice growth.In this view, Antarctica was not simply responding to climate change. The continent’s emerging landscape was actively shaping how climate changed as the ice sheet formed.