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.

A massive chunk of Greenland’s Petermann Glacier has broken away, forming an iceberg the size of Manhattan in what scientists say is the most significant Arctic calving event recorded in years.

As the dramatic event unfolded, the European Space Agency’s (ESA) Copernicus Sentinel-1 mission captured the breakup on August 4, as the 29-square-mile ice tongue detached from the eastern edge of Petermann Glacier.

The new “ice island,” also known as a tabular iceberg, is estimated to be close to 500 feet thick and was produced by an event that experts believe to represent the single largest loss of floating ice since 2012, and the most massive calving event anywhere in the Arctic since 2020.

Satellites Reveal a Rapid Iceberg Breakup

Evidence of an imminent calving event had begun showing months ago in the form of cracks in the glacier. On August 3, Sentinel-1 radar imagery revealed significant deterioration that was showing along the center of the glacier’s ice tongue.

Within hours, the massive section had separated, all as scientists and crew aboard the RRS Sir David Attenborough watched as cameras captured the remarkable display unfolding.

The crewmembers aboard the nearby vessel weren’t the only ones armed with cameras who were observing the massive breakup. For many years, an international team of researchers has been monitoring conditions on Petermann Glacier using Sentinel-1 imagery. Since 2019, a series of tracking and expanding fractures and other clear signs of instability have gradually worsened.

Additionally, interferometric measurements collected earlier in 2026 showed signs that deformation and fractures were spreading through the ice tongue in advance of a likely break, allowing scientists both on-site and observing via satellites in orbit to plan for the event.

Iceberg Break Antipated for Years

“Petermann Glacier has long been one of Greenland’s largest remaining ice tongues,” said University of Ottawa PhD student Adam Garbo, one of the many researchers involved in monitoring the glacier prior to the calving event.

“We’ve anticipated this break for years, and seeing it finally happen is remarkable,” Garbo said in a statement. “It’s a powerful reminder of how quickly these systems can change.”

This event was by no means the first time that the Petermann Glacier has undergone a major calving event. In 2008, 2010, and in 2012, similar significant ice losses were logged, although its floating ice tongue had remained mostly stable since that time.

The recent event signals the end of that period of relative stability. Additionally, researchers say two more sections—measuring around 97 and 87 square kilometers—are likely to detach as existing rifts continue to appear and gradually separate.

Sentinel-1 Spots a Massive Break Up Event

With the help of the ESA’s Sentinel-1C and the recently launched Sentinel-1D satellites, a remarkably detailed view of the calving event was made possible. During its commissioning period, Sentinel-1D and its predecessor satellite achieved one-day repeat synthetic aperture radar observations.

The resulting interferograms allowed scientists to examine how fractures propagated, and aalso how the floating ice responded to factors that include ocean water movement in the vicinity prior to the separation.

“The changes we observed on Petermann Glacier were occurring very rapidly in the lead-up to the iceberg calving event, so it was incredibly exciting to monitor the crack propagation with interferometry in near-real time,” said University of Leeds PhD student Molly Hammond in a statement.

Satellites like those with the Sentinel mission are especially useful for observations in polar regions since their radar systems allow researchers to observe the Earth’s surface even when cloud coverage or darkness would normally obscure visibility. This allows the ability to continuously monitor activity around these remote glaciers, and a chance to trek the new ice island as it continues to drift.

Ongoing Monitoring After a Rare Event

“This type of large tabular iceberg is relatively rare in the Arctic, making this calving event a unique opportunity to study how such a vast ice mass drifts, evolves and eventually breaks apart,” ESA researcher Martin Wearing said in a statement.

Although the iceberg currently poses no practical concerns, Environment and Climate Change Canada is currently monitoring the iceberg’s movement, and will provide assessments about whether it could pose any risk to Arctic shipping and offshore infrastructure in the months ahead.

Those monitoring efforts will likely continue into the foreseeable future, since massive ice islands as large as the newly formed iceberg can survive for many years before they eventually undergo fragmenting of their own, dispersing smaller pieces into the surrounding ocean. These smaller pieces can be much more difficult to track, and thereby could pose greater risks.

For now, scientists plan to continue watching the new ice island, which will offer new insights into Arctic glacier dynamics, as well as the changes that are impacting one of Greenland’s most closely watched glaciers.

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.

Antarctic guides walked away from their dream jobs after tourism’s environmental damage became impossible to ignore. “You’d see massive glacier calvings, and you’d just want to cry. But all the guests would be cheering. And you’d be like … ‘Can you not put two and two together?’” Those are the words of a former Antarctic [...]

Nearly 170 billion tons of ice melt off the Greenland Ice Sheet every year, but scientists don’t fully understand the process by which this melting occurs. Researchers in the past suggested that liquid water forms at the glacier’s surface, where warm air and sunlight melt the ice. This meltwater travels down through cracks in the glacier and along the bedrock beneath it and flows out to sea. 

However, some scientists view this model as too simple because it assumes water only flows downward and ignores how temperature affects water movement. They argue that an oversimplified melting model is unreliable for predicting how future ice sheets will behave.

One group of researchers tested this by investigating how water movement across Greenland is controlled by lakes beneath the ice sheet, called subglacial lakes. They monitored a newly discovered subglacial lake using high-resolution satellite images taken from 2012 to 2019 and 3D surface maps generated from the images. They focused on ice sheet changes from July 22 to August 1, 2014, during a suspected subglacial lake drainage event. A drainage event is like a water balloon that’s too full, bursting from excess pressure. 

They examined images of the Greenland ice sheet taken from Landsat-8, 3D surface maps from the Polar Geospatial Center, and data from ICESat and ICESat-2 taken in the summer of 2014. Based on these data, the researchers identified a 2-square-kilometer (0.8-square-mile) region of ice rising 10 to 15 meters (about 30 to 50 feet), forming a dome on the ice sheet’s surface. They suggested that this dome formed when a large, meltwater-fed lake developed on the bedrock beneath the ice sheet, pushing the ice upward. 

They also saw that on July 22, 2014, the dome began to collapse. Over the next 10 days, it dropped by 85 meters (about 280 feet), forming a basin. Using the dome’s dimensions, the researchers estimated that 90 million cubic meters, or about 3 billion cubic feet, of water drained from the lake at an average rate of 100 cubic meters, or about 3500 cubic feet, per second over the 10 days. This is roughly equivalent to 36,000 Olympic swimming pools draining at a rate of 1 pool every 25 seconds! 

The researchers also found that during the collapse, 40-meter-high (130-foot) ice blocks were uprooted about 1 kilometer (0.6 mile) downstream from the basin, followed by 6 square kilometers (about 2 square miles) of smooth ice. The researchers hypothesized that these features formed when water burst through the ice, flowed along its surface, and then reentered the ice sheet.

Next, they used data from Landsat 5, Landsat 9, the National Snow and Ice Data Center, and the U.S. Geological Survey to demonstrate that the drainage event also affected the surrounding environment. When the water reentered the ice sheet, it flowed beneath the Harding Glacier downstream. This influx of fast-moving water reduced pressure at the glacier’s base, slowing its movement. Simultaneously, the increased drainage beneath the Harding Glacier caused 500 to 600 meters (about 1,600 to 2,000 feet) of ice to break off its end. 

In response to these changes, the researchers hypothesized that subglacial waters rose to the surface rather than sinking to the bedrock because the ice sheet was frozen to it. To test this, they simulated temperatures at the base of the ice sheet using computer-generated thermal models. They input a range of likely bedrock temperatures and ice thicknesses to simulate possible conditions under the ice sheet. They found that all the simulations predicted the glacier’s base would remain below -5°C (23°F). At such low temperatures, the ice would be frozen to the bedrock before subglacial water could drain out. Since water couldn’t flow under the glacier, it was forced to travel upward. 

The researchers used these findings to develop a new conceptual model of how glacial meltwater moves. First, surface ice melts and flows into a subglacial lake. As meltwater accumulates, pressure builds at the base of the ice sheet, forming a dome on the surface. A drainage event causes the dome to collapse. As water moves downward through the glacier, it is blocked from reaching the base because the ice is frozen to the bedrock. The water then moves upward, bursts through the surface, travels across it, and eventually reenters the glacier before draining to the ocean.

The team concluded that water movement above, through, and below glaciers is interconnected. Destructive upward flow of meltwater, followed by downward flow beneath glaciers, can weaken ice sheet structure and alter downstream glacier dynamics. Their work highlights the need for more scientists to consider the processes driving glacial ice loss.

The post How do ice sheets melt? appeared first on Sciworthy.

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