Glacial Melting and New Island Formation

Overview

The lecture outlines how melting glaciers in Alaska have created a new island, illustrating the impact of climate change on landscapes.

NASA satellites observed that a new 2-square-mile island, known as Prow Knob, has emerged in southeastern Alaska.
Prow Knob was previously surrounded by the Alsek Glacier, which has since melted and retreated.
Melting ice flooded the area, leading to the isolation of Prow Knob as an island in Alsek Lake.

In 1984, images showed Prow Knob partly connected to the shore with most of it encased in ice.
Over four decades, the Alsek and Grand Plateau Glaciers steadily retreated eastward.
By summer 2025, Landsat 9 images showed the final separation of ice from Prow Knob.

The transformation is highlighted as a sign of global climate change, with rising temperatures accelerating glacier retreat.
The Alsek Glacier has retreated more than 3 miles since 1984.
Alsek Lake has nearly doubled in size, from about 17 to almost 30 square miles since 1984.
Increased meltwater runoff has contributed to the growth of a proglacial lake.

Continued glacier melting is expected, especially now that ice is no longer stabilizing Prow Knob.
Further changes in landscape and lake expansion may occur as warming persists.

Glacier Retreat — The process of glaciers shrinking back as ice melts faster than it is replenished.
Proglacial Lake — A body of water formed from glacier meltwater accumulating in front of a retreating glacier.
Prow Knob — The newly formed island, previously surrounded by the Alsek Glacier.
Alsek Glacier — A large glacier in southeastern Alaska that has undergone significant melting.
Alsek Lake — A lake that expanded due to glacier meltwater, now surrounding Prow Knob.

Review changes in glacial regions as indicators of climate change.
Study satellite imagery of Alsek Glacier and Prow Knob for further understanding.