The Thwaites Ice Shelf in West Antarctica is key to understanding ice shelf dynamics and their implications for global sea level rise. It represents one of the most rapidly changing areas in Antarctica, with the ice shelf itself the Thwaites Glacier could contribute up to 65 cm to sea level rise from its current drainage area. Study Wang et al. (2025) focuses on measuring and characterizing faults in this rapidly changing region, which are crucial for the structural integrity of ice shelves.

To overcome the limited measurements of vertical fracture structure, the researchers developed a new workflow. They used geolocated photon heights from NASA's ICESat-2 ATL03 satellite, which enabled the first measurements of vertical fractures across Thwaites from 2018 to 2024. The workflow includes a new multiscale adaptive binary segmentation (MABS) algorithm to generate surface height profiles and an improved object-oriented fracture detection algorithm. They introduced the fracture depth/freeboard ratio as a normalized metric to quantify the vertical extent of fractures and an indicator of structural damage.

Different behavior of the eastern and western parts

The study revealed significant differences in the behavior of ice fractures and flow between the eastern ice shelf and the western Thwaites ice tongue.

• Eastern part of the ice shelf: In this section, the intensity of the breaks intensified along the northwest shear zone and near the grounding line. A mutually reinforcing feedback loop was observed between increased ice breaking and accelerated ice flow. Ice flow in the eastern section accelerated significantly between 2018 and 2024, with a velocity increase of 136 % in the northwest shear zone. This acceleration is associated with an increased shear strain rate, which increased by almost 15-fold, and with longitudinal stretching near the grounding line, which increased by threefold. These changes indicate ongoing structural damage to the ice shelf.
• Western part of the glacier tongue: This section maintained a relatively stable zone of active rifting approximately 15 km downstream of the historical 2011 stranding line. Flow velocity changes were primarily confined to the unconfined lower section, with an overall slowing trend, while the upper section remained stable. This underscores the role of lateral margin conditions in controlling ice shelf behavior in the area of fractures and flow.

Connection with atmospheric and oceanic conditions

The study also explored potential links between fault and flow variability and atmospheric and oceanic conditions using reanalysis data.

• Atmospheric conditions: Significant atmospheric warming was observed in the Thwaites region from 2019 to 2022, particularly during the winter months, with the winter of 2019 recording an air temperature anomaly of approximately 5°C above the 1979-2010 average. These warm atmospheric conditions were associated with reduced sea ice concentration. Increased flow velocities on the eastern ice shelf and an increase in the break-to-free-edge ratio coincided with periods of warm winter temperatures and reduced sea ice.
• Ocean conditions: Although reanalysis of ocean data suggests an overall cooling trend along the Thwaites coast, there was a persistent warm water anomaly at shallower depths (10-200 m) near the eastern ice shelf. This warm water anomaly coincided with a significant decrease in sea ice concentration and may have facilitated the ascent of warmer water (Circumpolar Deep Water – CDW) to the ice shelf, which likely accelerated basal melting and promoted fracture growth in areas of high stress. In contrast, the region near the western ice tongue showed persistent cooling and sweetening over the same period, consistent with the observed slowdown in ice flow in this area.

These findings suggest that interactions between the atmosphere, sea ice, and ocean affect the structural integrity of the ice shelf through basal processes. If the damping effect of the eastern ice ridges continues to weaken, the likelihood of rapid retreat of the eastern ice shelf will increase significantly in the near future. The study highlights the need for future research that integrates satellite observations of fractures with numerical models of ice fracturing and flow to better understand the dynamics of ice shelf weakening and retreat. Spring

The entire study was published in the journal Journal of Geophysical Research Earth Surface .