Researchers have discovered nearly 1 billion tons of water equivalent locked within Utah’s rock glaciers. A team from the University of Utah and the Utah Geological Survey used 232 gravity measurements to map 1.55 million cubic meters of hidden ice beneath Mount Timpanogos, revealing vital subterranean freshwater reserves in warming mountain environments.
Mapping Subterranean Ice via Gravity Measurements
At first glance, Utah’s rocky mountain slopes may look completely dry, with loose stones and boulders covering the ground. But beneath some of those rocks lies an enormous store of frozen water. Researchers have now estimated that Utah’s rock glaciers contain about 0.99 gigatonnes, or nearly 1 billion tons, of water equivalent. These unusual formations are bodies of ice buried beneath thick layers of rock and debris, allowing them to survive in places where conventional glaciers cannot. Rock glaciers look nothing like the bright, exposed ice fields people normally associate with glaciers. They are instead masses of ice covered by layers of loose rocks and debris, with the ice slowly moving downhill beneath the surface. That rocky blanket can insulate the ice from warmth and sunlight, allowing these formations to persist in mountain environments that may no longer support conventional glaciers.
To look beneath the Timpanogos Rock Glacier, the team turned to a method that does not require drilling through the entire formation. Led by Bronson Cvijanovich alongside Michael S. Thorne, Surya Pachhai, Leif S. Anderson, Ivan Tochimani-Hernandez, Christian L. Hardwick, and Tonie van Dam, researchers from the University of Utah and Utah Geological Survey collected 232 gravity measurements across the site. As reported in their study, ‘The Internal Ice Content of Timpanogos Rock Glacier, Utah, USA From 3-D Bayesian Inversion of Gravity Data,’ published in the Journal of Geophysical Research: Earth Surface, the team used a three-dimensional Bayesian inversion to reconstruct the hidden structure.
Ice is substantially less dense than surrounding bedrock, meaning a sufficiently large buried ice mass creates a tiny but measurable reduction in gravitational acceleration. By mapping these variations, researchers estimated that the Timpanogos Rock Glacier holds an ice volume of about 1.55 million cubic metres, with an average thickness of 18.8 metres. The study indicates the entire formation is about 72% ice by volume, while its ice core is approximately 83% ice. That hidden reservoir is significant because its buried ice may persist for centuries, even while surface conditions appear relatively stable.
Fieldwork Challenges and Snowfall Accumulation
Uncovering these hidden reserves required rigorous fieldwork. In fall 2024, Bronson Cvijanovich led field teams on six trips to the site, carrying sensitive equipment up a five-mile trail and climbing approximately 3,500 feet to reach the rock glacier. The researchers used a sophisticated gravimeter to take readings at 232 locations about 25 meters apart. Leif Anderson stated, There’s a lot of ice hiding in Utah’s mountains.
Hikers walking over what seems to be normal rubble may be blissfully unaware that dozens of meters of ice could be underneath.
The researchers also explored how rock glaciers develop ice beneath their rocky surfaces. The process seems to be a combination of snowfall and rockfall beneath steep mountain slopes and cirques where rocks frequently break loose. Large rocks falling on areas of persistent snow can bury and protect the snow from melting, which adds ice to the rock glacier over time. Researchers found that years with heavy snowfall, cool summers and substantial rockfalls can contribute to ice accumulation, with more than 70 patches of debris-covered snow still existing at Timpanogos.
Global Implications for Changing Climates
To visualize the scale of the discovery, researchers compared the 1.55 million cubic metres of ice beneath Mount Timpanogos to the volume of roughly 600 Olympic-sized swimming pools. Using their measurements alongside data from other rock glaciers, the team developed a new area-volume relationship. This method generated an estimate of about 0.99 gigatonnes of water, equal to roughly 815,000 acre-feet, for Utah’s rock glaciers, which total 836 known formations. Furthermore, researchers estimate there may be around 50,000 worldwide, holding about 48 gigatons of water.
These reserves carry profound implications as climate change reduces conventional glacier ice. Rock glaciers can store water, provide refuges for cold-adapted species and, if destabilised, create hazards for communities below. However, scientists point out that not all rock glaciers are still gaining ice, as some have already lost their frozen cores. The Timpanogos Rock Glacier, however, appears to remain active and is still adding ice.
