High in the Teton Range, patches of ice tucked beneath some of the mountains’ most dramatic peaks are doing something that might not be obvious from a distance: they’re moving.
Grand Teton National Park is home to numerous glaciers, bodies of permanent ice that slowly flow downhill under their own weight. Scientists have been monitoring these glaciers for years, measuring their movement, seasonal snowpack, and changes in the amount of ice they contain.
Today, 11 exposed surface glaciers have been identified in the Teton Range. Some have lost so much ice that they may no longer be actively moving, meaning they could now be considered remnant glaciers rather than active glaciers.
Middle Teton Glacier is one of the glaciers scientists are watching most closely.
Located on the northeast side of the 12,804-foot Middle Teton, the glacier is the second largest in the range and is considered by researchers to be representative of the Tetons’ remaining glaciers.
Its accessibility also makes it particularly useful for long-term monitoring.
Modern monitoring efforts began in 2014, although scientists have been documenting glaciers in the Teton Range since the 1920s.
Park scientists visit Middle Teton Glacier throughout the season, including intensive surveys near the end of the winter accumulation period and again following the summer melt season.
During spring surveys, researchers measure snow depth and density and install stakes deep into the glacier. As the seasonal snowpack and underlying ice melt throughout the summer, the exposed portions of those stakes allow scientists to measure how much material has disappeared.
The stakes can also help researchers determine how quickly the glacier itself is moving.
Glaciers aren’t simply stationary patches of ice. Enough accumulated ice will deform and flow downhill under its own weight, which is one of the characteristics that separates an active glacier from a permanent snowfield or remnant ice body.
Scientists also use GPS surveys and time-lapse cameras to track changes in the Tetons’ glaciers. The cameras allow researchers to observe changes in snow cover, crevasses, ice movement, rockfall, and icefall over time.
The measurements have revealed significant changes.
Between 2014 and 2022, the surface elevation of the Teton Range’s exposed glaciers decreased by an average of 19 feet, 5 inches. Across that period, the average loss exceeded two feet per year.
The glaciers collectively lost an estimated 280 million cubic feet of ice during the same period.
The changes are part of a much longer trend.
Grand Teton National Park says all of the range’s glaciers have retreated since the late 1800s, although there have been shorter periods when some glaciers advanced.
The glaciers occupying the Tetons today are also much smaller than the enormous glaciers responsible for creating much of the landscape visitors see from the valley floor.
During the Pleistocene Ice Age, massive glaciers flowed through the region, carving the deep canyons and dramatic terrain that define the Tetons. Those large glaciers disappeared thousands of years ago.
The smaller glaciers found high in the mountains today primarily occupy shaded alpine cirques. Many are believed to have formed during the Little Ice Age, a cooler period that lasted roughly from 1400 to 1850, although research suggests Teton Glacier itself may have a considerably longer history.
Evidence of the Tetons’ glacial past is everywhere.
Glaciers carved the range’s distinctive U-shaped canyons and helped create many of the lakes scattered along the base of the mountains. They transported enormous quantities of rock, gravel, and sediment, leaving behind moraines and outwash plains that still influence the landscape today.
The remaining glaciers continue to play an ecological role.
Ice stored high in the mountains contributes meltwater during the summer, when much of the seasonal snow has already disappeared. Research cited by the National Park Service has found that glacier-fed streams can remain colder than comparable streams without glacial influence.
Those cold environments can be especially important for species adapted to them.
One example is Lednia tetonica, a stonefly found only in cold meltwater environments in the Teton Range. As surface glaciers retreat and the alpine environment changes, researchers are studying how the loss of cold-water habitat could affect species that depend on it.
Scientists are also paying increasing attention to another type of ice hidden throughout the Tetons.
Unlike exposed surface glaciers, rock glaciers contain mixtures of rock and ice covered by debris. Grand Teton researchers have identified 22 active rock glaciers in the range, along with more than 30 remnant rock glaciers that are no longer moving but still contain ice.
So far, those debris-covered glaciers appear considerably more resistant to ice loss.
From 2014 to 2022, researchers found that the surface elevation of rock glaciers decreased by an average of just under two feet. Exposed surface glaciers, by comparison, dropped an average of more than 19 feet.
That difference could make rock glaciers increasingly important as conditions in the Greater Yellowstone Ecosystem continue to change.
The National Park Service says temperatures above 7,000 feet in the region increased by approximately 2.5°F between 1950 and 2020. Scientists expect the Greater Yellowstone Ecosystem to continue transitioning from an environment dominated by snow toward one increasingly influenced by rain.
What happens to the Tetons’ remaining glaciers will provide researchers with another way to measure that transition.
Some of the smallest ice bodies have already changed dramatically. Teepe Glacier, located on the east face of Grand Teton, is no longer considered active. The National Park Service has previously warned that some of the range’s smallest remnant glaciers could disappear within decades.
Larger glaciers, including Teton Glacier and Middle Teton Glacier, could persist much longer, although exactly how long is difficult to predict.
For now, scientists will continue heading into the high country to measure them.
Visitors don’t necessarily need to make the same journey to see some of the park’s remaining ice.
Teton Glacier can be viewed from the Teton Glacier Turnout along Teton Park Road. Falling Ice Glacier on Mount Moran is visible from the Mount Moran Turnout, while Skillet Glacier can be seen from the Colter Bay area.
From a distance, they may look like small patches of snow and ice beneath the Tetons’ enormous peaks.
Look a little closer, however, and they tell a much bigger story. These glaciers are remnants of the processes that helped shape one of America’s most recognizable mountain landscapes, and scientists are now getting a remarkably detailed look at how they continue to change.
