Sentinel-1 captures major ice loss from Greenland glacier

The newly formed tabular iceberg, or ‘ice island’, covers an area about the same size of Manhattan and is estimated to be up to 150 metres thick.

Sentinel-1 radar imagery captured on 3 August showed pronounced deterioration along the centreline of the ice tongue. By the following day, the vast ice island had detached from the eastern side of the glacier.

Because Sentinel-1 carries a radar, it can observe day and night and through cloud cover, making it particularly well-suited to monitoring remote Arctic glaciers.

Using this Sentinel-1 radar imagery, an international team of researchers – partially funded through ESA’s FutureEO ARCTEX project – has been monitoring Petermann Glacier since 2019.

The collaboration brings together scientists from the University of Ottawa in Canada, the Universities of Stirling, Lancaster and Leeds in the UK, and the Canadian Ice Service of Environment and Climate Change Canada, who have been documenting the gradual growth of fractures and increasing signs of instability in the glacier’s floating ice tongue.

Interferometric observations of Petermann acquired in April also revealed deformation and fractures within the ice tongue, providing a detailed picture of changes that developed months prior to the calving.

Adam Garbo, a PhD student from the University of Ottawa, said, “Petermann Glacier has long been one of Greenland’s largest remaining ice tongues. We’ve anticipated this break for years, and seeing it finally happen is remarkable. It’s a powerful reminder of how quickly these systems can change.”

Petermann Glacier has a well-documented history of major calving events, including the formation of large ice islands in 2008, 2010 and 2012. However, since 2012, its floating ice tongue has remained relatively stable, despite several smaller-scale calving events.

The latest calving is unlikely to be the last major change at Petermann Glacier. Two further large ice islands, with estimated surface areas of approximately 97 and 87 sq km, could detach as existing rifts continue to propagate across the floating ice tongue.

Anna Crawford, from the University of Stirling, commented, “While large, tabular icebergs are relatively common in the Southern Ocean around Antarctica, Arctic ice islands are far rarer.

“By studying Arctic ice islands, we will gain knowledge that can be transferred across polar regions. This is critical for understanding how the calving and deterioration of ice islands impact glacier dynamics, sea-level rise and the ocean environment.”

The detailed Sentinel-1 interferogram showing the location and growth of fractures on Petermann Glacier was made possible because of one-day repeat Sentinel-1 synthetic aperture radar images captured in the Sentinel-1C and Sentinel-1D tandem phase during the commissioning of the newly launched Sentinel-1D satellite.

These data allowed very detailed measurements of fracture propagation across the ice shelf, and ice tongue surface motion with ocean tides, in the lead up to the iceberg calving event.

Molly Hammond, a PhD student from the University of Leeds, who processed the Sentinel-1 data, said, “The changes we observed on Petermann Glacier were occurring very rapidly in the lead up to the iceberg calving event, so it was incredibly exciting to monitor the crack propagation with interferometry in near-real time. This has demonstrated the incredible value of one-day repeat synthetic aperture data.”

ESA’s Martin Wearing noted, “This type of large tabular iceberg is relatively rare in the Arctic, making this calving event a unique opportunity to study how such a vast ice mass drifts, evolves and eventually breaks apart.

“Satellite missions such as Sentinel-1 provide the systematic, long-term observations needed to track these changes, helping scientists better understand the processes driving calving and the wider impacts on the polar environment, and ultimately the Earth system as a whole.

“Alongside Europe’s excellent Earth observation missions, we are pleased to see the ARCTEX project supporting this work and enabling further scientific investigation of the rapidly evolving Arctic.”

The research team will continue to observe both Petermann Glacier and the newly calved iceberg using satellite imagery, aerial observations and tracking data, following its movement and fragmentation over time. These measurements will provide further insight into the behaviour of large Arctic ice islands and the processes shaping the evolution of Petermann Glacier.

The calving also has practical implications for Arctic navigation and offshore operations.

Environment and Climate Change Canada is monitoring the iceberg’s trajectory and assessing potential risks to shipping routes and infrastructure. Such large ice masses can remain in the ocean for years, gradually breaking apart into smaller fragments that can be increasingly difficult to detect and track.