Glaciers

Nabesna glacier with Mt Blackburn in the background, Wrangell-St Elias National Park and Preserve.

NPS/Bev Goad

Approximately one quarter (4.6 million acres) of Alaska's glaciers exist within national parks. Glaciers require three conditions to form: abundant snowfall, cool summers, and the gravitational flow of ice. Glaciers form in land areas where annual snowfall is greater than annual snowmelt. Some areas in Alaska, such as the Harding Icefield in Kenai Fjords National Park, receives an average of 60 feet of snow each year. Large amounts of snowfall, combined with cool summers and gravity, form multiple, connected glaciers over time, known as an icefield.

Glaciers tell stories of the Earth's history; they shape the Earth's surface as they move and form valleys and mountains. Glacial ice documents weather and life from many years past. Tidewater glaciers are those that terminate in the sea. The ice that calves off these glaciers provide important habitat to ice-dependent species, such as seals.

What was the glacial extent in Alaska during the Pleistocene? Check out the Alaska PaleoGlacier Atlas.

Alaska's Shrinking Glaciers

Alaska is one of the most heavily glaciated areas in the world outside of the polar regions. Approximately 23,000 square miles of the state are covered in glaciers—an area nearly the size of West Virginia. Glaciers have shaped much of Alaska’s landscape and continue to influence its lands, waters, and ecosystems. Because of their importance, National Park Service scientists measure glacier change. They have found that glaciers are shrinking in area and volume across the state. 

The effects of climate change are felt more in high-latitude regions like Alaska than in most other regions of the world. Over a 50-year interval—between the 1950s and early 2000s—glaciers within Alaska national parks shrank by 8%. From 1985 to 2020, glacier-covered area in Alaska decreased by 13%, indicating that the rate of glacier loss accelerated in recent decades. As our climate continues to warm, glacial retreat will likely accelerate, profoundly impacting the landscape of Alaska and our parks for generations to come. 

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Learn more about how we understand glacier melt

Glacier monitoring and melt modeling on debris-covered Kennicott Glacier, presented at the 2021 meeting of the American Geophysical Union

Glaciers are a magnificent part of the landscape of Kenai Fjords National Park. They are responsible for carving the park's fjords, they nourish downstream ecosystems, and they provide recreational opportunities for visitors to the park. Although glaciers may appear to be permanent, unchanging features—things that change very slowly are often said to move at "a glacial pace"—glaciers are actually quite dynamic, changing in size in response to changes in their environment. How do we know that glaciers are changing in size? One method is to use photographs, taken by people on the ground or from satellites in space. By comparing photographs of the same location from different dates (repeat photography), we can monitor how glaciers change over time. Explore the new story map below to learn more.

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Glacier Terminology

Ablation

the retreat and degradation of glaciers

Advance

glacier flow exceeds ablation and the terminus extends beyond its previous point

Calve

process of ice breaking off at a glacier's terminus

Crevasse

a large crack in the surface of a glacier produced by the stress of glacial flow

Hanging

a glacier that clings to the side of a steep mountain or one that terminates at a cliff

Moraine

a deposit of rock debris shaped by glacial flow and erosion

Tidewater Glacier

a glacier that terminates in the sea and discharges icebergs and other small pieces of ice

Terminus

the lower end, or snout, of a glacier