Summer is the busiest time of year for iceberg activity in Greenland’s glacier-fed fjords, and 2026 delivered a particularly dramatic example. In August, a huge iceberg broke away from Petermann Glacier on Greenland’s northwest coast. About the size of St. Thomas in the U.S. Virgin Islands, it marked the largest calving event from any Arctic glacier since 2020.
Iceberg calving is a normal part of the life cycle of outlet glaciers, but scientists monitor these events closely for clues about longer-term signs of instability. Petermann is one of Greenland’s largest marine-terminating glaciers and helps control the flow of ice from the Greenland Ice Sheet into the ocean. Because of that role, changes in its stability could have implications for sea level rise.
A Giant Ice Island Breaks From Petermann Glacier
The summer 2026 calving was first identified on August 4 by Adam Garbo, a doctoral student in glaciology at the University of Ottawa, using imagery from the European Space Agency’s Sentinel-1 mission. Garbo and an international group of researchers have been relying on remote sensing to monitor Petermann Glacier and follow changes in its floating ice tongue.
According to the team, the large flat-topped iceberg, known as an “ice island,” measured just over 76 square kilometers (29 square miles) when it separated from the glacier. That made it the largest iceberg to break from Petermann since the 2012 event, which produced an ice island covering 130 square kilometers. Earlier major calving events occurred in 2008 (31 square kilometers) and 2010 (just over 250 square kilometers).
Scientists had actually been preparing for an even larger break. Garbo and his colleagues were watching one of several major rifts that appeared likely to eventually cut across the entire ice tongue. Instead, the glacier fractured along a different crack.
“What surprised us was that the calving instead followed a different fracture, producing a smaller ice island than we had originally anticipated,” Garbo said.
As of late August, two large rifts were still present. Researchers expect them to eventually release new ice islands measuring roughly 94 square kilometers and 84 square kilometers, although no one knows exactly when those breaks will occur.
The Iceberg Heads Toward Nares Strait
Glaciologist Mauri Pelto of Nichols College has also been tracking the iceberg using imagery from NASA-USGS Landsat satellites. After separating from the glacier, the berg moved down Petermann Fjord toward Nares Strait at an average speed of about 3 kilometers per day during its first week.
It eventually approached the point where the fjord meets Nares Strait and collided with a small rocky outcrop called Joe Island (Joe Ø). The encounter was captured by the OLI (Operational Land Imager) aboard Landsat 9 on August 23 and August 24. A closer look at the August 24 scene is shown at the top of this article.
Joe Island sits near the entrance to Petermann Fjord, putting it directly in the path of many ice islands leaving the glacier. Such collisions can trigger the beginning of an iceberg’s breakup. One notable example occurred when a 2010 ice island struck Joe Island and split into two pieces.
Pelto noted that icebergs from Petermann are generally thinner and more fragile than those produced by Greenland glaciers such as Jakobshavn and Helheim. They are also much thinner than the enormous icebergs that break away from Antarctica.
A Collision That Failed to Break It Apart
Despite that fragility, the new Petermann ice island remained intact after striking Joe Island.
“We were certainly watching closely as it interacted with Joe Island and were impressed that it survived the interaction without further fragmentation,” Garbo said.
At the time it broke away, the ice island was estimated to be less than 150 meters thick. Winds and surface currents later carried it out of Petermann Fjord, while satellite observations showed it pivoting away from Joe Island and moving southwest through Nares Strait.
Its journey will gradually become more destructive. Tides, winds, ocean currents, and melting will continue weakening the iceberg until it eventually fractures into smaller pieces.
Where Greenland’s Ice Islands Can Go Next
Some thicker icebergs that break from tidewater glaciers without floating ice shelf extensions can scrape along the seabed or become grounded inside a fjord. Ice islands from Petermann may instead travel farther before running aground. Many have eventually become “grounded” near the coasts of Coburg and Baffin islands.
Garbo and his colleagues noted that Petermann ice islands and the fragments they produce can travel long distances through Arctic waters. Along the way, they can create hazards for ships, marine operations, and infrastructure.
At the same time, they play another role in the ocean. As the ice slowly melts, it releases freshwater into surrounding waters, carrying the influence of Greenland’s glaciers far beyond the fjord where the iceberg first broke free.
