The study found that 13 of the 19 glaciers showed signs of substantial retreat, four were relatively stable and two had advanced. The findings also include trends in which glacier types are disappearing the fastest. This nearly 670,000-acre national park is home to a variety of glaciers: some terminate in the ocean, others in lakes or land. The study, from the University of Washington and the U.S. National Park Service, was published Aug. 5 inJournal of Glaciology“superior.
“These glaciers are a big draw for tourism in the park — they’re one of the main things people see,” said study lead author Taryn Black, a doctoral student in Earth and Space Sciences at the University of Washington. “Park managers have some information from satellite imagery, aerial photographs and repeat photography, but they want a more complete picture of changes over time.”
The data show that glaciers that terminate in lakes retreat the fastest. Glaciers of this type include the popular Bear Glacier and Pedersen Glacier glaciers. Between 1984 and 2021, Bear Glacier retreated 5 kilometers, while Pedersen Glacier retreated 3.2 kilometers over the same period.
“In Alaska, the retreat of many glaciers is caused by climate change,” Black said. “These glaciers are at really low elevations. This may cause them to get more rain in winter than snow, and in addition to warmer temperatures, This is consistent with other climate studies in the region.”
One surprising discovery is the Holgate Glacier, which as a tidal glacier ends in the ocean, has advanced in recent years. Local boat operators have reported seeing newly exposed land near the edge of the glacier in 2020. But the new analysis shows that the entire glacier has been advancing for about five years and appears to be going through regular cycles of advancing and retreating. The edges of most other tidal glaciers were relatively stable during the study period.
All six land-terminated glaciers showed intermediate responses, with most retreating, especially in summer, but at a slower rate than lake-terminated glaciers. During the study period, the only advancing glacier was the land-terminated Paguna Glacier, which was covered in rock debris from a landslide caused by the 1964 Alaska earthquake. These rubble shield the glacier’s surface from melting.
To do the calculations, Black used 38 years of satellite images taken in the fall and spring to trace the contours of each of the 19 glaciers — about 600 in total. She visually inspected each image to map the location of the glacier’s edge. Black used a similar approach in a recent study to calculate the rate of retreat of the end glaciers in the western Greenland ocean.
New data from Alaska provides a baseline for studying how climate change — including rising temperatures, as well as changes in the type and amount of precipitation — will continue to affect these glaciers. All glaciers in the study are considered marine glaciers because they are influenced by a warm, humid oceanic climate.
The findings of this study have direct applications for park managers. These numbers help quantify the changes that have occurred and will continue to occur in the glacier and its surrounding environment.
“If we don’t understand the habitats and processes that take place on our lands, we can’t manage those lands well,” said co-author Deborah Kurtz from the U.S. National Park Service.
As the park’s physical science program manager, Kurtz is also interested in changes to the surrounding river, lake and landscape ecosystems and how to communicate these changes to the public.
“Explain andeducateIt’s also an important part of the National Park Service’s mission,” Kurtz said. “These data will allow us to provide scientists and visitors with more details on what is happening to each specific glacier, helping everyone better understand and appreciate our presence in the region. The rate of landscape change experienced. “
