Glacier Monitoring in Denali and Wrangell-St. Elias, 2024

U.S. Geological Survey glaciologist Emily Baker builds a new weather station on a bedrock ridge near Kahiltna Glacier, Denali National Park and Preserve. Image from the National Park Service's page.

In spring and fall 2024, Central Alaska Network principal investigator Michael Loso and scientists from the U.S. Geological Survey Alaska Science Center surveyed Kahiltna Glacier in Denali National Park and Preserve and Kennicott Glacier in Wrangell-St. Elias National Park and Preserve. The updated program now measures snow and melt at six sites on each glacier, and the work continues.

Why monitor glaciers

Glaciers grow and shrink in direct response to climate, which makes them valuable indicators of climate change and its effects. As Alaska's glaciers retreat, they can add significantly to sea level rise, reduce water supply to major rivers, reshape watersheds and trigger landslides. Knowing local trends helps anticipate the size and timing of such events and prepare for them. Both glaciers are well known and heavily used for recreation, and are important assets to their parks and communities.

For park managers, the monitoring:

• keeps current information on some of the parks' most spectacular resources for scientists and visitors;
• shows the local effects of climate change with direct, familiar examples;
• helps predict where glaciers are headed, for planning infrastructure and resources;
• supplies data to glaciology, meteorology, geomorphology and other sciences.

How it is done

The aim is to document long-term, climate-driven change on both glaciers, which means recording when and where each gains or loses mass and what the local weather is doing. The key measure is annual balance: the net mass gained or lost over a year, from accumulated snow minus summer melt.

• Spring: scientists dig snow pits to measure the snow that has fallen since the last season, drilling a core from the bottom of the pit when they cannot dig to the base, and weigh known volumes of snow to measure density.
• Stakes up to 12 meters long show accumulation and melt by how much is buried or exposed on each visit.
• Weather stations on or near the glaciers record precipitation, temperature, wind speed and solar radiation.

Work on Kahiltna Glacier began in 1991 and has expanded in recent years; work on Kennicott Glacier began in 2015.

Results

Because snow, ice and water differ in density, balances are converted to snow water equivalent. The clearest pattern is the expected one: balances are higher at higher, colder, usually snowier elevations. High sites also seem to respond to climate differently from low ones, probably because they react differently to summer and winter temperatures. Years differ, too: 2018 was a "good" year on Kahiltna, while 2023 was an especially good one on Kennicott, at least at lower elevations. Together with seasonal balances, these results show how the glaciers are responding to different aspects of the changing climate.

Annual mass balance on Kahiltna Glacier (left) and Kennicott Glacier (right), by site elevation. National Park Service figure.

Sources

• National Park Service, Central Alaska Inventory and Monitoring Network: "Central Alaska Glacier Surveys 2024," a resource brief.