In Montana, average temperatures have risen 1.8 times faster than the global average, and Glacier National Park’s ice bodies are taking the heat.
From 1900 to 2006, annual average temperatures in the state increased by 1.33 degrees Celsius, or about 2 degrees Fahrenheit. The rest of the world has seen an increase on average of 0.74 degrees Celsius, U.S. Geological Survey physical scientist Eric Pietzch noted at Science and History Day in the Park.
Pietzch, glacier expert Dan Fagre, and others have spent decades tracking snow characteristics through space and time. They’re trying to get a comprehensive picture of how glaciers respond to climate change.
In the Rocky Mountains West, snow represents an important water source for drinking and irrigation, and provides unique meltwater habitats. But with warming temperatures, habitats and resources could be threatened.
Since 1890, Montana and other regions have seen more frequent hot days above 90 degrees Fahrenheit, and will experience fewer days below freezing. Additionally, temperature is rising faster at higher elevations, which puts even more pressure on glaciers.
Snow accumulates zero to 11 meters per winter and is redistributed across ice bodies. Pietzch noted that the scientists use drills and stakes to measure accumulation in spring and melting each fall, with about eight stake stations on Sperry Glacier alone. Different parts of each glacier experience different amounts of ice loss due to redistribution of snow and varying melt patterns, and years may vary. A cold winter and mild summer could allow an increase in glacial extent, while a warmer winter and hot summer could cause a lot of melting.
However, all glaciers in the Park and elsewhere are shrinking on a longer-term scale. Since 1966, the 37 named glaciers in the Park have shrunk 39 percent on average. For some, it’s more like an 85 percent loss.
One projection model, with the 2 degree increase in Celsius per century that world leaders have agreed to allow, has Sperry Glacier completely gone in 2100. There are now only 26 glaciers in the Park larger than 25 acres, and the loss could be even greater — only areal extent is measured, not ice thickness or volume, so melting could be eroding glaciers faster than previously thought.
Glaciers on steep, shadowed north faces tend to retreat less quickly. But those at lower elevations, like the iconic Grinnell Glacier, melt even faster than the average. A calving event at Grinnell a couple years ago led to an 11-acre loss between 2015 and 2016.
Glaciers are essential to the Park ecosystem, keeping spring temperatures cold and providing cold water for threatened native fish and insects. They also provide most of the water for high alpine habitats and some water to rivers and streams in lower elevations. Even mammals like wolverines rely on the snowpack, as they den under deep snows in the high country.