Alaska’s Excelsior Glacier has been retreating since 1941, forming a lake named Big Johnston. The glacier’s melting rate has doubled since 1994, according to a blog post from the American Geophysical Union (AGU) website. The lake, in turn, has doubled in size in the past 24 years. With Big Johnston Lake now five times the size of Central Park, Excelsior Glacier has completely separated into its eastern and western tributaries, according to a NASA article.
Mauri Pelto is the glaciologist at Nichols College who wrote the AGU post. “To see the amount of expansion and retreat in that amount of time is exceptional,” he told NASA.
According to Pelto, the high melting rate has been caused by warm temperatures and calving, the process by which ice at the edge of a glacier breaks off. This glacial breaking filled Big Johnston Lake with icebergs. But as Excelsior Glacier recedes farther away from the lake, icebergs are disappearing.
Since the glacier has retreated to a higher slope, it is no longer calving at a high rate. With this difference, the glacier “will still retreat, but it will slow down a lot—more on the order of tens of meters per year instead of hundreds,” Pelto told NASA.
Staff from the Johnstone Adventure Lodge, a local resort, captured images of the glacier that show its radical transformation from 2016 to 2019.
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