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

As glaciers around the world recede due to climate change, national park managers need to know what’s on the horizon to prepare for the coming. New study from University of Washington and Nationwide Park Services measures 38 years of change for glaciers in Kenai Fjords Country Park, a magnificent gem approximately two hours south of Anchorage.

The study, published August 5 in The Journal of Glaciology, reveals that 13 of 000 glaciers show substantial retreat, four are relatively stable and two have advanced. It also finds trends in which types of glaciers are disappearing fastest. The nearly 670 000 acre park is home to various glaciers: some end in the ocean, others in lakes or on land.

“These glaciers are a big attraction for tourism in the park – they are one of the main things that people come to see,” said lead author Taryn Black, a PhD student in Earth and Space Sciences at UW. “Park managers had information from satellite images. but they wanted a fuller understanding of changes over time.”

Data shows that the glaciers that end the lakes, including the famous Bear Glacier and Pedersen Glacier, are retreating the more quickly. Bear Glacier retreated 5 kilometers (3 miles) between 1984 and 2021, and Pedersen Glacier retreated 3.2 kilometers (2 miles) during that time.

“In Alaska, much of the retreat of glaciers is due to climate change,” Black said. “These glaciers are at very low altitude. This may cause them to receive more rain in winter rather than snow in addition to warming temperatures, which is consistent with other climate studies in this region.”

A surprising discovery was that the Holgate Glacier, which as a tidal glacier ends at the ocean, has advanced in recent years. Local boat operators had reported seeing newly exposed land near the edge of the glacier in 2020. But the new analysis shows that the entire glacier has been progressing for around 5 years and appears to be going through regular cycles of advance and retreat. The edges of most other tidal glaciers were relatively stable during the study period.

The 6 land-terminating glaciers all showed an intermediate response, most retreating, especially during the summer months, but at a slower rate than the lake-ending glaciers. The only other glacier that advanced during the study period was the land-tipped Paguna Glacier, which is covered in rock debris from a landslide caused by the 1964 in Alaska. This debris insulates the glacier floor from melting.

To do the math, Black has used 38 years of images captured by satellites in the fall and spring to trace the outlines of each of the 19 glaciers – a whole of approximately 600 contours. She visually inspected each graphic to map the placement of the edge of the glacier. Black has used a similar approach in recent research to calculate the rate of retreat of marine-terminated 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 the types and amount of precipitation — will continue to affect these glaciers. All the glaciers in the study are considered maritime glaciers because they are subject to the hot and humid maritime climate.

The study has immediate application for managers of Park. These numbers help quantify the changes that have occurred and will continue to glaciers and their immediate environments.

“We cannot manage our lands well if we do not understand the habitats and the processes that take place there,” said co-author Deborah Kurtz of US Countrywide Park Assistance in Seward, Alaska. The physical sciences of the park, Kurtz is also interested in changes to the ecosystems of rivers, lakes, and surrounding landscapes, and how to communicate those changes to the general public.

“Interpretation and education are also an important part of Countrywide Park Assistance’s mission,” Kurtz said. “These data will allow us to provide scientists and visitors with more detail about the changes taking place on each specific glacier, helping everyone to better understand and appreciate the rate of landscape change we are experiencing in this region.”

This study was carried out as part of an internship initially planned at the Kenai Fjords countrywide park. Black instead conducted the research remotely from Seattle and visited the local glaciers of Mount Rainier. A portion of this research was funded by the National Park Provider’s Long Term Park Leaders Program, a partnership between the Ecological Culture of America and US National Park Assistance.

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