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New study calculates retreat of glacier edges in Alaska’s Kenai Fjords National Park

New study calculates glacier edge retreat in Alaska's Kenai Fjords National Park

Holgate Glacier, shown here in June 2009, ends on the shore and is a popular kayaking destination, especially in the summer when the ice is calving. Local residents had recently observed land exposed to the terminus, but the new analysis shows the glacier has progressed over the past 5 years. Credit: US National Park Service

As glaciers retreat globally due to climate change, national park managers need to know what’s on the horizon to prepare for the future. A new study from the University of Washington and the National Park Service measures 38 years of change for glaciers in Kenai Fjords National Park, a beautiful gem about two hours south of Anchorage.

The study, published Aug. 5 in The journal of glaciology, notes that 13 of the 19 glaciers are retreating significantly, four are relatively stable, and two have advanced. It also finds trends in which glacier types are disappearing the fastest. The nearly 670,000-acre park is home to several glaciers: some end in the ocean, others in lakes or on land.

“These glaciers are a big draw for tourism in the park — they’re one of the most important things people come to see,” said lead author Taryn Black, a UW doctoral student in Earth and space sciences. “Park managers had some information from satellite imagery, aerial imagery and repetitive photography, but they wanted a more complete understanding of changes over time.”

The data shows that glaciers that flow into lakes, including the popular Bear Glacier and Pedersen Glacier, are the fastest to retreat. Bear Glacier retreated 5 kilometers (3 miles) between 1984 and 2021, and Pedersen Glacier retreated 3.2 kilometers (2 miles) during that period.

“In Alaska, a lot of glacier retreat is caused by climate change,” Black said. “These glaciers are at a very low elevation, potentially getting more winter rain than snow in addition to warming temperatures, which is consistent with other climate studies in this region.”

New study calculates glacier edge retreat in Alaska's Kenai Fjords National Park

Nearly half of Kenai Fjords National Park is covered in glacial ice. Glaciers play an important role in shaping the landscape of the park. Bear Glacier, shown here in September 2019, retreated more than 5 kilometers (about 3 miles) from 1984 to 2021, according to the new study. The lagoon at the base of the glacier grows as the glacier retreats. Credit: US National Park Service/Deborah Kurtz

A surprising finding was that the Holgate Glacier, which ends as a tidal glacier at the ocean, has progressed in recent years. Local boat operators had reported seeing newly exposed land on the edge of the glacier in 2020. But the new analysis shows that the overall glacier has been advancing for about 5 years and appears to be going through regular cycles of advance and retreat. The rims of most other tidal glaciers were relatively stable over the study period.

The six terminating glaciers all showed an intermediate response, with most retreating, especially in the summer months, but at a slower rate than the glaciers terminating the lake. The only other glacier to advance during the study period was the land-locking Paguna Glacier, which is covered in rock debris from a landslide caused by the 1964 Alaska earthquake. This debris insulates the glacier’s surface from melting.

To make the calculations, Black used 38 years of images captured by satellites in the fall and spring to trace the contours of each of the 19 glaciers — about 600 contours in all. She visually inspected each image to map the position of the glacier’s rim. Black has been using a similar approach lately Research to calculate the rate of retreat of sea-ended glaciers in West Greenland.

The new data for Alaska provides a basis for studying how climate change — including warmer air temperatures, as well as changes in both types and amount of precipitation — will continue to affect these glaciers. All glaciers in the study are considered maritime glaciers because they are subject to the warm, wet maritime climate.

New study calculates glacier edge retreat in Alaska's Kenai Fjords National Park

Located on the Kenai Peninsula in Alaska, Kenai Fjords National Park is dominated by two large ice fields. The 19 glaciers included in the study are shown as blue dots. Although Alaska’s glaciers make up only a small fraction of the planet’s glacial ice, they are losing ice faster than any other glacial region outside of Antarctica and Greenland. Credit: US National Park Service/Deborah Kurtz

The study is directly applicable to park managers. These numbers help to quantify the changes that have occurred and will pass for the glaciers and their immediate surroundings.

“We can’t properly manage our land if we don’t understand the habitats and processes that take place there,” said study co-author Deborah Kurtz of the US National Park Service in Seward, Alaska.

As the park’s Physical Science program manager, Kurtz is also interested in the changes in the surrounding ecosystems of rivers, lakes, and landscapes, and how to communicate these changes to the public.

New study calculates glacier edge retreat in Alaska's Kenai Fjords National Park

These colored contours show the edges mapped for each of the 19 glaciers studied in Kenai Fjords National Park. The color scale ranges from purple for 1984, the earliest year in the satellite images, to red for 2021, the most recent year. A few of the glaciers are Bear Glacier (a), Aialik Glacier (b), and Pedersen Glacier (c), all of which have retreated. Holgate Glacier (d), on the other hand, has progressed in many places. Thirteen of the 19 glaciers showed significant retreat. Credit: Taryn Black/University of Washington

“Interpretation and education are also an important part of the National Park Service’s mission,” Kurtz said. “With this data, we can provide scientists and visitors with more detail about the changes occurring on each specific glacier, helping everyone understand and appreciate the speed of landscape changes we are experiencing in this region.”

This research was done as part of an internship originally intended to take place in Kenai Fjords National Park. Black instead did the remote research from Seattle, visiting local glaciers on Mount Rainier. Part of this research was funded by the National Park Service’s Future Park Leaders program, a collaboration between the Ecological Society of America and the US National Park Service.

Coastal glacier retreat linked to climate change

More information:
Taryn Black et al, Maritime glacier retreat and endpoint area change in Kenai Fjords National Park, Alaska, between 1984 and 2021, Journal of Glaciology (2022). DOI: 10.117/jog.2022.55

Provided by the University of Washington

Quote: New study calculates glacier edge retreat in Alaska’s Kenai Fjords National Park (2022, Aug 5), retrieved Aug 5, 2022 from https://phys.org/news/2022-08-retreat-glacier-edges-alaska-kenai. html

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