New satellite imagery from NASA’s Earth Observatory has revealed a new island in Alaska’s Glacier Bay National Park. Prow Knob, a small mountain that used to be surrounded by the Alsek Glacier, stands as a roughly five-square-kilometre island in the newly formed Alsek Lake. This happened when the glacier melted and pulled away, leaving the mountain isolated in the middle of the newly formed Alsek Lake.
Two satellite images, one captured on 5 July 1984 and another captured on 6 August 2025, depict the transformation in remarkable detail. Based on the satellite images, the separation occurred between 13 July 2025 and 6 August 2025. According to glaciologist Mauri Pelto at Nichols College, both arms of Alsek Glacier have retreated more than 5 kilometres since 1984, when the glacier was first spotted.
The appearance of the new island raises a concern about the pace at which glaciers are melting. “The global trend of glacier retreat and disappearance due to anthropogenic climate is an enormous crisis,” said Jason Briner, a professor of geology at the University at Buffalo.
Currently, melting glaciers hold enough water to cause a global sea-level rise of about half a metre. This would significantly threaten many coastal areas and lead to more frequent and powerful storm surges.
From 1984 to the present, Alsek Lake has expanded considerably, growing from 45 to 74 square kilometres, as a direct result of the surrounding glacier’s melting. The expansion of the lake is fuelled not only by meltwater from the Alsek Glacier but also from nearby proglacial lakes like Harlequin and Grand Plateau. This growth is a recent phenomenon, as the Alsek Glacier was connected to the northern part of the Grand Plateau Glacier until approximately 1999.
Experts also caution that the emergence of this new island is an alarming sign. According to the US Department of Agriculture, glaciers in Alaska are melting at a concerning rate, twice as fast in comparison to their pace between 1960 and 2004.
“Often we have this sense that glaciers are this really static thing,” said Kiya Riverman, a glaciologist at Oregon State University. “They’re almost like living, breaking creatures that change a little bit every day.”
In response, the United Nations designated 21 March 2025 as the Inaugural World Day for Glaciers. This initiative comes as glaciers around the world are rapidly shrinking due to climate change, a trend that is particularly pronounced in Alaska, where temperatures are rising at a rate two to three times faster than the global average.
