Antarctica's Hektoria Glacier experienced a significant collapse between early 2022 and spring 2023, retreating approximately 25 kilometers (15 miles) in 15 months. During one two-month period, the glacier's terminus receded by over 8 kilometers (5 miles), marking the fastest retreat of grounded glacial ice recorded in modern history.
Scientists analyzed the event using remote sensing data, concluding that the glacier's shape and structure contributed to the rapid collapse. Hektoria Glacier, located on the Antarctic Peninsula, extends from land into the ocean, forming a floating ice tongue. Researchers observed the loss of this ice tongue and a large section of grounded ice resting on a flat bedrock area. The loss of grounded ice directly contributes to sea level rise.
Historical Context and Retreat Phases
The collapse of Hektoria Glacier is linked to events dating back to 2002, when the Larsen B ice shelf shattered. This ice shelf had previously stabilized Hektoria and nearby glaciers. Following its disappearance, glaciers in the region began thinning and retreating.
By 2011, landfast sea ice in the Larsen B embayment near Hektoria's terminus expanded, providing temporary support that allowed the glacier to advance slowly. This stability ended in January 2022 when the landfast sea ice broke apart, likely due to powerful ocean swells. After this support vanished, Hektoria Glacier began to change rapidly.
During the austral summer of 2022, the floating ice tongue steadily broke apart through repeated calving events, resulting in a retreat of approximately 16 kilometers. The glacier stabilized temporarily during the 2022 austral winter, but satellite laser measurements from NASA's ICESat-2 mission indicated continued thinning beneath the surface.
Buoyancy-Driven Calving and Future Monitoring
Researchers determined that the remaining ice was still grounded during the 2022 austral spring, based on earthquakes detected beneath the glacier.
Researchers determined that the remaining ice was still grounded during the 2022 austral spring, based on earthquakes detected beneath the glacier.
Analysis showed the ice rested across a broad, relatively flat section of bedrock, known as an ice plain. This terrain allows seawater to move beneath the glacier during high tide, temporarily lifting sections of ice. When the ice becomes sufficiently thin, large portions can detach and break away.
Scientists believe this process, known as buoyancy-driven calving, initiated the glacier's second phase of retreat, during which Hektoria lost an additional 8 kilometers in length. Naomi Ochwat, a glaciologist at the University of Innsbruck and lead author of the study, is investigating whether other glaciers face similar risks as temperatures rise around the Antarctic Peninsula, leading more glaciers to lose protective ice tongues and become tidewater glaciers.
New satellite technologies, such as the NISAR (NASA-ISRO Synthetic Aperture Radar) and SWOT (Surface Water and Ocean Topography) satellites, are expected to enhance understanding of rapid glacier retreat. Ted Scambos, a senior research scientist at the University of Colorado Boulder, noted that NISAR's centimeter-accurate movement measurements will be useful for structural evaluations of glaciers in the region. Ochwat expressed interest in SWOT's potential contributions to understanding rapid glacier changes.
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