A section of Greenland's Petermann Glacier roughly the size of Manhattan has broken free and drifted into Nares Strait, marking the floating ice tongue's largest single loss since 2012 and one of the most significant Arctic calving events observed in more than a decade.
The European Space Agency said radar images from the Copernicus Sentinel-1 mission tracked a rift widening across the glacier's floating extension for months before a roughly 76-square-kilometer slab, estimated up to 150 meters thick, separated from the eastern side of the tongue on Aug. 4. Because Sentinel-1 carries radar rather than an optical camera, it can image the glacier through the Arctic's near-constant cloud cover and winter darkness, letting researchers watch the fracture propagate in near-real time long before the ice actually let go.
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.
Martin Wearing, ESA
A floating shelf, not the ice sheet itself
Petermann is one of Greenland's largest glaciers, and unlike most of the ice sheet's margins, it ends not in a cliff but in a long floating tongue that extends many kilometers out over the ocean, similar to shelves found around Antarctica. Because that tongue is already afloat, its calving does not by itself add much to sea-level rise, the same way an ice cube already in a glass does not raise the water line further as it melts. The concern for glaciologists is what the tongue does upstream: it acts as a buttress, and its loss can allow the grounded ice behind it to flow toward the ocean faster.
ESA said the newly detached ice island is now the largest piece to separate from Petermann since 2012, when a similarly sized slab broke away and eventually fragmented as it drifted south. The agency's satellite record of the glacier stretches back decades and shows the floating tongue has generally shortened since the early 2000s, though calving at Petermann has historically come in large, episodic events rather than steady retreat.
Researchers funded through ESA's ARCTEX project, who have monitored Petermann with Sentinel-1 interferometry since 2019, say the glacier is not done shedding ice. Two more rifts are propagating across the remaining floating tongue, and the agency estimates they could eventually release additional ice islands of roughly 97 and 87 square kilometers if the fractures continue to spread. This account rests on direct satellite observation of a physical event rather than a modeled projection, though how much further ice the glacier sheds, and how quickly, remains to be seen in the coming Sentinel-1 passes.
