The Alsek Glacier in southeastern Alaska once encircled a small rocky mound known as Prow Knob. But in recent decades, the retreat of the glacier has left Prow Knob as a freestanding island.
A century ago, the Alsek Glacier extended 3 miles beyond Prow Knob, ending at Gateway Knob, which sits at the opposing end of what is now Alsek Lake. This summer, the glacier finally lost contact with Prow Knob, as shown in satellite imagery from NASA.
The 2-square-mile island is now entirely surrounded by Alsek Lake, which is fed by meltwater from surrounding glaciers. The lake has nearly doubled in size in just the last four decades.
Alaska is home to 19,000 glaciers that collectively span an area nearly the size of West Virginia, but as temperatures rise, the ice is rapidly retreating. Alaska is warming two to three times faster than the Earth as a whole, and its glaciers are shedding more than 66 billion tons of ice each year.
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