When examining ice shelves, glaciologists employ a method that, at least in theory, is similar to a structural engineer checking a bridge for stress fractures before it collapses. You examine the fissures. You measure them, monitor their growth, try to figure out what’s causing them, and, if your models are accurate enough, attempt to forecast when and where the next one will form. The issue with doing this on a glacier the size of a small nation in one of the world’s most hostile and remote environments is that there has never been enough data, the models have always been oversimplified, and the fractures have always been occurring more quickly than science can keep up.
This problem is most noticeable on the Thwaites Glacier in West Antarctica. Thwaites, the world’s widest glacier, is about 80 miles wide, or about the distance between New York City and Philadelphia. It has earned the colloquial moniker “Doomsday Glacier” due to a simple calculation: if its ice shelf completely collapsed, the glaciers behind it would become unstable, potentially raising global sea levels by up to 11 feet. Not right away. Not for ten years. However, in a geological timeframe that can now be measured in centuries rather than millennia, and possibly more quickly if the fracturing speeds up in ways that are not fully captured by current models. The remainder of the glacier is held back by the ice shelf that stretches from Thwaites, a floating tongue of ice attached to the land that protrudes onto the ocean’s surface.
The architectural element that supports a Gothic cathedral’s exterior walls is similar to a flying buttress, according to Richard Alley, a professor of geosciences at Penn State. There is nothing holding the wall in place if the buttress is removed. “We’ve seen ice shelves break off,” Alley remarked. “We’ve never seen one grow back.”
Key Facts: Arctic & Antarctic Ice Shelf Fracture Research
| Topic | Scientific tracking of rapid ice shelf fractures, primarily at Thwaites Glacier, West Antarctica |
| Lead Researcher | Shujie Wang, Assistant Professor of Geography, Penn State University |
| Key Co-Author | Richard Alley, Evan Pugh University Professor of Geosciences, Penn State |
| Glacier in Focus | Thwaites Glacier (“Doomsday Glacier”) — approximately 80 miles wide, West Antarctica |
| Sea Level Risk | Total Thwaites collapse could trigger up to 11 feet of sea level rise |
| Annual Antarctic Ice Loss | ~136 billion tons per year |
| Satellite Used | NASA ICESat-2 (data analyzed 2018–2024) |
| Earlier Study Reference | 2002 Larsen B Ice Shelf collapse — 1,250 sq mi broke apart in ~5 weeks |
| Pine Island Glacier | Contributes more to current sea level rise than any other glacier; studied via seismic icequake tracking |
| Key Finding | More aggressive fracturing in Thwaites’ eastern section; relative stability in the west |
| Reference Links | Measuring Antarctic Ice Fractures – Penn State · Tracking the Cracking – PMC/Geophysical Research Letters |
Using satellite data from NASA’s ICESat-2 instrument, which has been measuring surface elevations across glaciers, ocean heights, and other natural features since its launch, a team led by Shujie Wang, an assistant professor of geography at Penn State, has been creating a new technique to track precisely how the Thwaites ice shelf is fracturing. After analyzing ICESat-2 data from 2018 to 2024, Wang’s team developed a two-step workflow that produces detailed visual cross-sections of fractures as they change over time and high-resolution profiles of surface elevations. The end product is something more akin to a living map showing the locations of ice cracks, their depth, and whether they are expanding more quickly or more slowly from season to season. “We know little about fractures, and their behavior is much more complex than conventional models suggest,” Wang stated. The observation is straightforward and significant because the models that guide sea level projections—the models that coastal planners, policymakers, and infrastructure engineers rely on—have been constructed using precisely those traditional simplifications.
The new data showed a more spatially specific deterioration rather than a uniform one throughout the Thwaites shelf. The western portion of the ice shelf is relatively stable, while the eastern portion is fracturing more violently. The researchers identified warmer winter air temperatures, decreased sea ice, and altered ocean circulation beneath the shelf as potential contributors to that asymmetry, though the exact causes are still unknown. Each of those elements is linked to the larger warming of the Southern Ocean, which has been bringing warmer water to the base of the Thwaites shelf for decades. This warming eats away at the ice from below in a way that is not apparent at the surface but manifests itself in the ice’s thinning and accelerated flow toward the sea. Faster ice movement is encouraged by worsening fractures. Stress is increased by moving more quickly. More fractures result from increased stress. When you take into account the scope of what is being described, the researchers’ description of this as a “domino effect of fissures and instability” is both technically correct and genuinely unsettling.
An alternative and complementary perspective on the same issue is provided by the seismological method of researching ice fractures. Previous studies on Pine Island Glacier, which is a part of the larger West Antarctic Ice Sheet and contributes more to current sea level rise than any other single glacier in the world, used an on-ice seismic network to record what scientists refer to as icequakes, which are the vibrations caused when ice fractures, calves, or shifts. These icequakes propagate as flexural gravity waves, a kind of hybrid seismic and water wave specific to floating ice shelves, where the buoyancy of the water and the elasticity of the ice combine to produce a signal that can be detected and examined at considerable distances from its source. The Pine Island seismic data demonstrated that fracture growth occurs in bursts rather than smoothly and continuously, with water flow controlling or limiting the rate at which crevasses open. Every icequake in the study was equivalent to about 10 meters of vertical cracking in the ice, occurring over a duration of about 30 seconds. This is fast enough to produce a detectable seismic signature, but slow enough to imply that water is passing through the fracture as it opens.
When attempting to explain what a destabilized ice shelf actually looks like in practice, researchers most frequently turn to the 2002 collapse of the Larsen B Ice Shelf on the Antarctic Peninsula. Before it broke apart over the course of about five weeks in the northern Antarctic summer of 2002, Larsen B had been deteriorating for years due to atmospheric and oceanic factors gradually weakening its structural integrity. After being stable for thousands of years, 1,250 square miles of ice simply broke apart into icebergs and vanished in about a month. The processes leading to that collapse were thoroughly documented by Wang’s earlier research, and the lessons learned from Larsen B are directly influencing how scientists view Thwaites. At Thwaites, the pattern of weakening, the part surface meltwater plays in hydraulic fracturing, and the acceleration of ice flow after the shelf disappears are not theoretical issues. These processes are currently taking place in various areas of the shelf at different speeds.
Reading this research gives me the impression that what scientists are developing is a sort of early warning system—not the dramatic alarm bell of a news cycle, but the more subdued, technically challenging task of figuring out what the signals look like before the threshold is reached. Wang stated as much herself, characterizing the new method as a link between prediction and observation. Zhengrui Huang, her doctoral candidate, has compiled satellite data for over 40 Antarctic ice shelves, creating a three-dimensional dataset of fracture features that the team intends to make available to the general public as an open-source resource. In years or decades, when decisions about coastal adaptation and infrastructure investment will depend on having trustworthy answers to questions that are still being worked out in university labs and polar field camps today, this kind of unglamorous scientific infrastructure—data pipelines, processing workflows, archived satellite passes—will make better predictions possible.
