The Taku Glacier in Alaska is the thickest Alpine glacier in the world and one of the few glaciers that had managed to avoid major melting. This is no longer the case. Climate change does not discriminate and comes for everyone. The most recent analysis shows Taku is shrinking as it is finally beginning to melt.
Researcher Mauri Pelto studied Taku as well as 249 other glaciers worldwide, using data spanning decades. Unlike the other glaciers, Taku was stable and was until the late 1980s. However, precise observations show that this was just the calm before the storm. Observational data from the Operational Land Imager on NASA’s Landsat 8 satellite starkly show that this sturdy glacier has begun thawing. The findings are published in the journal Remote Sensing.
“This is a big deal for me because I had this one glacier I could hold on to,” Pelto, a glaciologist at Nichols College, told Kasha Patel at the NASA Earth Observatory. “But not anymore. This makes the score climate change: 250 and alpine glaciers: 0.”
Taku is the largest glacier in the Juneau Icefield, which comprises 40 large valley glaciers and 100 smaller ones. Unlike any other glacier in the field, Pelto and colleagues discovered that between 1946 and 1988, Taku continued to advance and gain mass. Given this mass-gaining trend, it's perhaps not surprising that its thickness from surface to bed is 1,480 meters (4,860 feet).
“We thought the mass balance at Taku was so positive that it was going to be able to advance for the rest of the century,” explained Pelto. “A lot of times, glaciers will stop advancing for quite a few years before retreats start. I don’t think most of us thought Taku was going to retreat so quickly.”
The Landsat 8 data was used by Pelto to measure the extent of Taku's transient snowline, the point at which snow deposition stops and only ice is left. The average height of the snowline increased by 85 meters (280 feet) from the 1946-1985 period to the 1986-2018 period. In images that compare the 2014 extension to 2018, one can see how the end of the glacier is retreating.
“To be able to have the transition take place so fast indicates that climate is overriding the natural cycle of advance and retreat that the glacier would normally be going through,” said Pelto. “Taku Glacier is being exposed to melting it hadn’t before, which will drive new changes.”