'Doomsday Glacier' of Antarctic

 Antarctic ice is cracking with 'Doomsday Glacier' can trigger accelerated destabilization 

A team of researchers have started to analyse ice fractures in the ‘Doomsday Glacier’. The Thwaites Glacier in West Antarctica is known for its rapid changes, fractured surface and fast ice flows. A total collapse of the roughly 80-mile-wide Thwaites Glacier, the widest in the world, would trigger changes which could lead to 11 feet of sea-level rise, according to scientists who study Antarctica. Thwaites Glacier in West Antarctica, often called the "Doomsday Glacier", is one of the fastest-changing ice–ocean systems on Earth, and its future remains a major uncertainty in global sea-level rise projections. One of its floating extensions, the Thwaites Eastern Ice Shelf (TEIS), is partially confined and anchored by a pinning point at its northern terminus. Over the last two decades, TEIS has experienced progressive fracturing around a prominent shear zone upstream of this pinning point. A new study provides comprehensive details on how progressive disintegration has been taking place over the last two decades. To better predict fractures which could lead to such a collapse, and to better understand the processes driving changes in Antarctic ice shelves, a team developed a new method to evaluate cracks which destabilize ice shelves and accelerate those losses. They reported their technique for analyzing fractures in the ice shelves, which are floating tongues of ice connected to land that extend out to float on ocean water. The study was led by Debangshu Banerjee, a recent graduate student from the Centre for Earth Observation Science (CEOS), together with Dr. Karen Alley (Assistant Professor, CEOS) and Dr. David Lilien (Assistant Professor, Indiana University Bloomington and former Research Associate at CEOS).

The research is part of the TARSAN (Thwaites-Amundsen Regional Survey and Network) project, one of the components of the International Thwaites Glacier Collaboration (ITGC), a major US–UK research initiative studying the processes driving change in the Thwaites Glacier of West Antarctica. Renowned glaciologists Dr. Ted Scambos, Dr. Martin Truffer, Dr. Adrian Luckman, and Dr. Erin Pettitt have also been a part of this research. Drawing on two decades (2002–2022) of satellite imagery, ice-flow velocity measurements, and in-situ GPS records, the team traced the evolution of fractures within the TEIS shear zone and their connection to changes in ice dynamics. The analysis revealed that the gradual development of these fractures led to the shelf's progressive detachment from its pinning point, causing accelerated flow upstream and a loss of mechanical stability. The researchers focused on measuring vertical fractures in the Antarctic ice sheet, which shrinks by around 136 billion tons every year but is still the largest on Earth, over time. The group specifically evaluated ice fractures in the Thwaites Glacier, the so-called “Doomsday Glacier” in West Antarctica, to develop their method, which could help reveal the structural integrity of ice shelves and if, and when, they might give way, the researchers said.

“We know little about fractures, and their behaviour is much more complex than conventional models suggest,” said lead author Shujie Wang, assistant professor of geography and faculty associate in the Earth and Environmental Systems Institute at Penn State. “Conventional models depend largely on simplified models and scarce, hard-to-obtain field observations.” Modeling ice-shelf retreat is complex, especially due to limited data on ice fracturing. This challenge is pronounced at the Thwaites Ice Shelf, an extension of the Thwaites Glacier which is known for its rapid changes, fractured surface and fast ice flow, according to the researchers. They said they see the Thwaites shelf as a bulwark against further disintegration of the glacier. The study identifies four distinct stages in this weakening process and offers two key insights. First, the fractures developed in two phases: an initial propagation of long, flow-parallel fractures, followed by shorter fractures oriented perpendicular to the direction of ice flow. Second, the researchers found evidence for a positive feedback mechanism between fracture-induced damage and ice acceleration, an amplifying cycle which hastened the shelf's disintegration in recent years.

Among their discoveries, the researchers found more aggressive fracturing in the Thwaites shelf’s eastern part and relative stability to the west. Although they did not determine certain causes for the differences, they said warmer winter air, reduced sea ice and changes in the ocean circulation beneath the ice shelf are potential contributors to fracture growth which require more research. Worsening fractures promote faster ice flow and a domino effect of fissures and instability within ice formations. The research highlights how the pinning point, once a major stabilizing force for the TEIS, has gradually transitioned into a destabilizing agent through four distinct stages. This pattern of ice-shelf disintegration may serve as a warning for other Antarctic ice shelves which are currently showing similar signs of weakening. The continued loss of these floating ice shelves could have significant implications for the Antarctic Ice Sheet's future contribution to global sea-level rise and a threat to the world.