New clues to the formation of our planet’s oldest and largest ice sheet could help resolve a longstanding enigma about the southernmost continent.
Around 34 million years ago, Antarctica’s ice sheet began to take shape during a period when global temperatures were predominantly warmer than they are at present. The exact reason why such a large portion of Earth’s water would be subsumed into a massive ice sheet under such conditions has long perplexed researchers.
Now, a new study published in the journal Science suggests that clues to the mystery may exist beneath the ice itself, according to researchers who point to geological evidence that could help explain what led to the formation of Antarctica’s glaciers during a comparatively warm period in our planet’s history.
Clues to Why a Continent Froze
The East Antarctic Ice Sheet (EAIS) holds enough frozen water that it could raise sea levels around the world by more than 50 meters if a sudden, total melting event were ever to occur. Fortunately, scientists don’t anticipate that happening any time soon, although questions over what caused the formation of the largest mass of ice on our planet have remained one of the most predominant mysteries about Antarctica’s ancient history.
Based on geological evidence and paleo-climatological proxy data, the ice sheet’s formation occurred near the transition between the Eocene and Oligocene eras around 34 million years ago, marking a significant step along our planet’s path toward the cooler conditions that prevail today, even amid anthropogenic factors that contribute to ongoing climate changes.
As far as the causes behind this, scientists have long pointed to a reduction in atmospheric carbon dioxide as one potential driver of glaciation in Antarctica. However, this explanation also leads to questions: namely, that if falling CO2 and global cooling are believed to be the main factors behind the formation of Antarctica’s ice, then similar freezing should have occurred close to the North Pole as well.
Curiously, evidence suggests that glaciation in Earth’s northernmost regions didn’t begin catching up to its southern counterpart for another 20 to 25 million years. But what might account for this?
An Ancient Climate Missing Link
The new research, led by scientists at the University of Southampton in collaboration with an international team of researchers from Durham University and several other institutions, points to Antarctica’s changing landscape as a likely missing piece to this ancient puzzle.
“Antarctica’s land surface was gradually lifted to the point where ice could gain a permanent foothold, even while the surrounding polar oceans as well as global temperatures remained surprisingly warm,” said Thomas Gernon, a Professor of Earth Science at the University of Southampton and the study’s lead author.
By employing models that helped the team map the evolution of the Antarctic landscape, they were able to successfully reconstruct the ancient geological processes going all the way back to the original breakup between Africa and Antarctica that reshaped East Antarctica. This continental breakup led to the formation of a coastal escarpment in the region identified today as Dronning Maud Land, where an elevated plateau rose to nearly two kilometers, and extended close to 2,000 kilometers inland.
Over the 100 million years that followed, a wave of uplift and erosion gradually migrated inland toward Antarctica’s Gamburtsev Mountains, a process which would recur again during the Eocene, further elevating the region and increasing the amount of ancient Antarctica’s landmass that was above the permanent snow line, all of which occurred roughly 15 million years before mass-scale glaciation would begin on the continent.
Based on the team’s models, these major changes to the landscape shifted East Antarctica above the threshold where ice-sheet growth could begin occurring, the onset of which began around 45 million years ago.
Combined Factors Behind Antarctica’s Freeze
Another factor the team identified involves how the large-scale glaciation also caused more sunlight to be reflected away from Earth due to the icy surface’s light coloration, a process known as albedo feedback. The team believes this reflected sunlight may have contributed to as much as an additional degree Celsius of total global cooling.
That cooling alone, the researchers note, would not have been enough to cause widespread glaciation across the Northern Hemisphere, which generally features lower elevations.
Overall, the findings do indicate that Earth’s transition into an icehouse wasn’t something that was driven solely by climate. Instead, what seems most likely is that slow geological transformations occurring over many millions of years were likely to have been a primary contributor to this process, raising Antarctica’s landscape enough to facilitate ice sheet formation, and revealing how the evolution of landscapes can ultimately reshape the climate of an entire planet.
The recent study, “Continental breakup–driven uplift instigated East Antarctic Ice Sheet formation,” appeared in the journal Science.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.