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2d ago

NASA Images Show Alaska’s Prow Knob Has Become an Island as Alsek Glacier Retreats

Scientists call the detachment a marker of human-driven glacier loss, raising risks from calving, outburst floods, landslides.

© NASA Earth Observatory
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Overview

  • Landsat 9 data show the final separation occurred between July 13 and August 6, 2025, when the last ice pulled away from Prow Knob.
  • The new island is an approximately 2-square-mile mountain that once stood as a nunatak within the Alsek Glacier and is now encircled by Alsek Lake.
  • Since 1984, Alsek Lake has nearly doubled in area, growing from about 17 to nearly 30 square miles, as the Alsek Glacier has retreated more than three miles.
  • NASA attributes the transformation to climate change, with the loss of ice contact making nearby ice more prone to calving and increasing the potential for glacial lake outburst floods.
  • The National Park Service says the shift is effectively irreversible and is monitoring ongoing changes as scientists describe a regional "new lake district" that includes growth in Alsek, Harlequin, and Grand Plateau lakes.