Giant Greenland Iceberg Slams Into Joe Island — and Survives

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. 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, so changes in its stability could have implications for sea level rise.

The 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. The flat-topped iceberg, known as an "ice island," measured just over 76 square kilometers when it separated, the largest to break from Petermann since a 130-square-kilometer event in 2012. Earlier major calvings occurred in 2008 (31 square kilometers) and 2010 (just over 250 square kilometers). Two large rifts remain in the glacier and are expected to eventually release further ice islands of roughly 94 and 84 square kilometers, though no one knows exactly when.

Glaciologist Mauri Pelto of Nichols College tracked the iceberg using NASA-USGS Landsat satellite imagery. It moved down Petermann Fjord toward Nares Strait at an average speed of about 3 kilometers per day in its first week, then collided with a small rocky outcrop called Joe Island, an encounter captured by the Landsat 9 satellite on August 23 and 24. Such collisions can trigger a breakup: a 2010 ice island that struck Joe Island split into two pieces.

The new Petermann ice island, estimated at less than 150 meters thick, remained intact after the collision. "We were certainly watching closely as it interacted with Joe Island and were impressed that it survived the interaction without further fragmentation," Garbo said. Winds and currents later carried it southwest through Nares Strait, and its journey will gradually become more destructive as tides, winds and melting weaken it until it eventually fractures.

Petermann ice islands and their fragments can travel long distances through Arctic waters, creating hazards for ships and infrastructure, while also releasing freshwater into surrounding seas as they melt. Many such fragments have eventually run aground near the coasts of Coburg and Baffin islands.