The Doomsday Glacier Is Getting Closer and Closer to Irreversible Collapse
Known as “Doomsday Glacier,” the Thwaites Glacier in Antarctica is one of the fastest-changing glaciers on Earth, and its future evolution is one of the biggest unknowns when it comes to predicting global sea level rise.
The eastern ice shelf of Thwaites Glacier is supported at its northern end by a ridge of the ocean floor. However, over the past two decades, cracks in the upper parts of the glacier have multiplied rapidly, weakening its structural stability. A new study from the International Thwaites Glacier Collaboration (ITGC) presents a detailed record of this gradual collapse process.
Researchers at the Center for Earth Observations and Science at the University of Manitoba, Canada, analyzed observational data from 2002 to 2022 to track the formation and propagation of cracks in the sea ice shear zone. They found that as the cracks grew, the connection between the ice shelf and the mid-ocean ridge weakened, accelerating the flow of ice upstream.
The crack in the ice shelf widens in two stages
The study reveals that ice shelf weakening occurred in four distinct phases, with crack growth occurring in two stages. In the first phase, long cracks appeared along the ice flow, gradually extending eastward. Some exceeded 8 km in length and extended across the entire plateau. In the second phase, numerous short cross-flow cracks, less than 2 km long, appeared, doubling the total length of the cracks.
Analysis of satellite images showed that the total length of cracks increased from about 165 km in 2002 to about 336 km in 2021. At the same time, the average length of each crack decreased from 3.2 km to 1.5 km, with a notable increase in small cracks. These changes reflect a significant change in the stress state of the ice shelf, that is, in the interaction of forces within its structure.
Between 2002 and 2006, the ice shelf accelerated as it was pulled by fast-moving currents nearby, generating compressive stress on the anchor point, which initially stabilized the shelf. After 2007, the shear zone between the shelf and the western ice tongue collapsed. The stresses concentrated around the anchor point, leading to the formation of large cracks.
Since 2017, these cracks have completely penetrated the ice shelf, cutting the connection with the anchorage. According to the researchers, this accelerated the flow of ice upstream and made the mooring a destabilizing factor.
Collapse of the feedback loop
One of the most significant findings of the study is the existence of a feedback loop: cracks accelerate the flow of ice and, in turn, this increased speed generates new cracks. This process was clearly recorded by the GPS devices the team deployed on the ice shelf between 2020 and 2022.
During the winter of 2020, the upward propagation of structural changes in the shear zone was particularly evident. These changes progressed at a rate of approximately 55 kilometers per year within the ice shelf, demonstrating that structural collapse in the shear zone has a direct impact on upstream ice flow.
