The Earth Observatory of NASA confirmed the formation of a new island in the coastal plain of southeast Alaska, as a result of the accelerated retreat of the Alsek Glacier.
The protagonist is Prow Knob, a small mountain that until recently was connected to the glacier. In the summer of 2025, satellite images revealed that the ice had completely withdrawn, leaving this landmass surrounded by Lake Alsek, which has significantly grown in recent decades.
From glacier to lake: accelerated transformation since 1984
Landsat images show the advance of water over the ice in four decades of monitoring.
The evolution of the landscape was documented by TM (Thematic Mapper) sensors on Landsat 5 and OLI-2 (Operational Land Imager-2) on Landsat 9. In 1984, the Alsek Glacier still reached Gateway Knob, about 5 km west of Prow Knob.
By then, part of the perimeter had already turned into the lake shore. In 1999, the retreat intensified, disconnecting Alsek from the Grand Plateau Glacier. Finally, between July and August 2025, Prow Knob was completely isolated, becoming a glacial island.
Glacial retreat: global and local consequences
The loss of ice not only alters the landscape but also exacerbates multiple environmental crises.
The phenomenon observed in Alaska is part of a global trend with profound impacts:
- Rising sea levels: melting water increases ocean volume, affecting coastal areas and displacing communities
- Freshwater scarcity: glaciers are natural reservoirs; their loss compromises the supply for consumption, agriculture, and energy
- Climate alterations: as glacial albedo disappears, Earth absorbs more heat, accelerating global warming
- Risks to biodiversity: species adapted to cold ecosystems face habitat loss and ecological stress
- Increase in natural disasters: melting can cause avalanches, landslides, and glacial lake outburst floods
- Impact on human health: melting releases ancient microorganisms, posing potential health risks
Prow Knob: from geographical feature to symbol of climate change
The mountain, named by glaciologist Austin Post, now represents irreversible transformation.
The name “Prow Knob” was assigned by glaciologist Austin Post in 1960, inspired by its resemblance to a ship’s prow. Today, that same formation becomes a visual testimony of glacial retreat, visible from space and documented through decades of satellite science.
