'New' island emerges from melting ice in Alaska

A satellite photograph of Alsek Lake and the new island of Prow Knob as Alsek Glacier retreats. — Alaska's Prow Knob (the big island on the right of the lake) used to be surrounded by ice. (Image credit: NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey.)

A 'new' island has appeared in the middle of a lake in southeastern Alaska after the landmass lost contact with a melting glacier, NASA satellite images reveal.

The landmass, named Prow Knob, is a small mountain that was formerly surrounded by the Alsek Glacier in Glacier Bay National Park. However, Alsek Glacier has been retreating for decades, slowly separating itself from Prow Knob and leaving a growing freshwater lake in its wake.

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An annotated satellite image of Prow Knob surrounded by ice in 1984. — Alsek on July 5, 1984. (Image credit: NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey.)

"Along the coastal plain of southeastern Alaska, water is rapidly replacing ice," Lindsey Doermann, a science writer at the NASA Earth Observatory, wrote in the statement. "Glaciers in this area are thinning and retreating, with meltwater forming proglacial lakes off their fronts. In one of these growing watery expanses, a new island has emerged."

Alsek Glacier used to split into two channels to wind its way around Prow Knob, which has a landmass of about 2 square miles (5 square kilometers). In the early 20th century, the glacier extended across the now-exposed Alsek Lake and as far as Gateway Knob, about 3 miles (5 kilometers) west of Prow Knob.

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The late glaciologist Austin Post, who captured aerial photographs of Alsek in 1960, named Prow Knob after its resemblance to the prow (pointed front end) of a ship. Post and fellow glaciologist Mauri Pelto, a professor of environmental science at Nichols College in Massachusetts, previously predicted that Alsek Glacier would release Prow Knob in 2020, based on the rate it was retreating between 1960 and 1990, according to the statement. The glacier has therefore clung on to its mountain for slightly longer than initially predicted.

Prow Knob completely separated from Alsek Glacier between July 13 and Aug. 6, according to the statement.

Many of Earth's glaciers are retreating as the planet gets warmer due to climate change. Last year was the hottest year for global average temperatures since records began, while 2025 has been marked by a string of record-breaking and near-record-breaking hot months.

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Patrick Pester is the trending news writer at Live Science. His work has appeared on other science websites, such as BBC Science Focus and Scientific American. Patrick retrained as a journalist after spending his early career working in zoos and wildlife conservation. He was awarded the Master's Excellence Scholarship to study at Cardiff University where he completed a master's degree in international journalism. He also has a second master's degree in biodiversity, evolution and conservation in action from Middlesex University London. When he isn't writing news, Patrick investigates the sale of human remains.

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