NPS In the early light of a summer morning, a team of physical scientists from Grand Teton National Park begins their ascent up Garnet Canyon, on route for Middle Teton Glacier (MTG). The trip is routine; the glacier monitoring crew makes the journey to MTG, and other glaciers in the range, throughout the season. There is a rich history of glacier monitoring in the Teton Range. Researchers have been documenting the condition of the range’s glaciers since the 1920s, though methods have changed drastically since then. Modern monitoring efforts began in 2014. Within the Greater Yellowstone Ecosystem, higher elevations are experiencing the most extreme changes in climate. Between 1950 and 2020, the average temperature at elevations above 7,000 feet, rose by 2.5°F. The effects of climate change are revealed in the condition of Grand Teton’s glaciers. Between 2014 and 2022, the average ice loss was over two feet per year. This is not a local phenomenon either. Globally, deglaciation is expected to reduce glacial mass by between 26 and 41 percent by the year 2100. Glaciers are powerful indicators of climate trends. Mapping their activity grants researchers insight on the entire region. Small glaciers—like the ones you’ll find tucked away in the Tetons’ cirques—make up the majority of global glacial area. Yet, they are understudied. The accessibility of the Teton glaciers provides, in their succession, an opportunity to explore the lifecycle and ecological role of small, cirque glaciers. Monitoring Methods
NPS / Churchwell The Teton glaciers are visited routinely throughout the ablation season. Most visits focus on installing timelapse cameras, taking repeat photographs, monitoring meteorological sensors, and collecting streamflow measurements. Timelapse cameras and repeat photographs attempt to capture a glacier’s activity visually. Repeat photos are taken from the same locations season after season, typically at a spot that has a good view but no place to install a camera. Timelapse cameras take photos at set intervals from opportune vantage points, either strapped or staked onto rock or tree. They are left for the entire ablation—or melting—season. In September of 2023, a Cyclapse camera was installed above MTG to take photos year-round. Researchers want to know how elements of the snow regime, like avalanche cycles, differ throughout the seasons. They also want to know whether annual snow depositions are changing. If Cyclapse cameras can consistently survive the winter, they could capture patterns in surface structure and snow distribution throughout the accumulation season. Generally, monitoring methods are shifting from qualitative to more quantitative methods (from descriptive to numerical). The goal with the new Cyclapse cameras is to compliment quantitative metrics with a robust set of year-round qualitative data. Together, they can tell a holistic story of glacial activity. Meteorological sensors collect climate metrics to accompany glacier data. Numerous air temperature loggers are deployed across the range. One pyranometer, measuring solar radiation, is installed at the Lower Saddle, between the Middle and Grand Teton. The direct shortwave radiation of sunlight is a unique driver from ambient air temperature. Both cause melt, but a warm, cloudy day will have less ablation than a sunny day of the same air temperature. Researchers measure solar radiation to help determine a glacier’s albedo—the fraction of sunlight its surface will reflect. Just as black asphalt captures more heat than lighter toned concrete, a glacier will capture more heat with reduced snow cover, as ice and debris are exposed. At places of stream outflow, loggers are installed to measure depth and temperature. Stream discharge is also collected manually on monitoring trips. Together these metrics are used to analyze seasonal trends in meltwater. Researchers are trying to compare patterns in glaciated versus non-glaciated regions. They have had difficulty isolating single-source channels. While this has prolonged the search for suitable study sites, it also highlights the complexity of alpine stream systems and the importance of subterranean ice. Most methods of direct glacier monitoring are concerned with spatial measurements: area and volume. These can be used to determine one of the most important metrics in glacier monitoring, mass balance—the difference between how much a glacier gains in accumulation and loses in ablation. Methods to measure mass balance are shifting to include more remote sensing, as opposed to strictly on-the-ground fieldwork. 
NPS LiDAR (Light Detection and Ranging) imagery provides an emergent method to map glacial change. LiDAR is a form of remote sensing that measures reflection of light off the ground. The time it takes for a light pulse to reflect back to the device corresponds with the distance it has traveled. With LiDAR flight surveys, the physical science team maps elevation across the glacier surfaces. Comparing these surveys across time shows changes in elevation, and a representation of mass balance. LiDAR flights were taken across the range in the summers of 2014 and 2022. Glaciers can have seasonal snow on their surface late into the summer, so the differencing is representative of general elevation change, as opposed to just ice loss. Similar results were seen across the different glaciers. For MTG, the average surface change was an elevation loss of a little over fourteen feet. This corresponded with a total snow and ice loss of over 37 million cubic feet. One result of the LiDAR differencing (measuring the distinction between two maps) surprised researchers. The debris fields skirting the edge of MTG’s visible ice also showed elevation change and movement. This suggests a body of subterranean ice stretches wide under the glacier’s rocky surroundings, including in the popular Moraines camping zone. 
NPS / Grubb Eyes on Middle Teton GlacierAlong with its accessibility, MTG is the second largest glacier and considered representative of the range. This makes it a prime site for further monitoring. The Physical Science Team conducts more intensive surveys of MTG at the cusps of the accumulation and ablation seasons. The accumulation season typically ends in late May. With heavy snow conditions, the team accesses the glacier by ski mountaineering. The trip consists of probing for snow depth, digging pits for snow density, and installing ablation stakes, which will be monitored throughout the summer. Ablation stakes are shot into the glacier with a steam drill. These stakes are made up of segments of PVC pipe, strung together and pre-marked with depth measurements. As the season progresses, and seasonal snowpack melts, the upper segments of pvc are exposed, and eventually collapse at joint points. 
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NPS Depth measurements can be paired with snow density to determine how much water is contained in some amount of snow (snow water equivalent, or SWE). Using the marks on the ablation stakes, SWE can inform how much water is lost to melting. The amount of water lost from melting ice can be determined similarly with ice depth and densities. Another purpose of the ablation stakes is to measure the velocity of MTG’s movement. Glaciers flow downslope, under their own weight. The process accelerates during ablation due to internal meltwater. As the ice creeps down the mountain slope, the stakes creep with it. By taking GPS measurements at the time of installation, and with each following visit of the season, the team can assign a rate to the glacier’s movement. Currently, MTG’s ice is flowing at an average rate of just under 20 feet per year. In 2015, a Ground Penetrating Radar (GPR) unit was used to map ice thickness in reference to the bedrock resting under MTG. GPR is similar to LiDAR, but its measurements are subsurface. The GPR device is mounted on a sled and sends electromagnetic pulses into the ice as two people tow it across the glacier’s surface. According to Daniel McGrath, an external researcher who performs GPR work on MTG, the 2022 survey found the glacier’s mean ice thickness to be approximately 95 feet, reaching a maximum of about 177 feet. Paired with geodetic elevation surveys, this data can be used to show the change in ice thickness over time. Geodetic surveys are conducted in the fall, at the end of the ablation season. They are technical expeditions, undertaken in the company of the Jenny Lake Climbing Rangers. With the surface stripped of seasonal snow, blue glacial ice is exposed. A GPS device is mounted to a staff-like survey rod, which is carried across the glacier, along a predetermined grid. As the glacier loses ice, the surface elevations will sink closer to the bedrock. Between 2016 and 2021, MTG’s ice thickness dropped as much as 21 feet along its extent. 
NPS / Grubb Evolving Glaciers
NPS / Grubb Research in the Tetons has revealed the importance of rock glaciers to maintain water storage and provide refuge for alpine species. Surface glaciers have a uniform, often exposed, icefield. Rock glaciers have a mixed matrix of rock and ice, entirely hidden under a layer of debris. The rocky exterior may have a lower albedo—more absorption of solar radiation—but the cold environment within is insulated, and the internal ice remains active. The monitoring program has found rock glaciers to be far more resilient than their exposed counterparts. Between 2014 and 2022, the surface of rock glaciers decreased by an average of 1 foot and 10 inches, while surface glaciers dropped an average of 19 feet and 5 inches. Similarly, the total volumetric loss over the same period was about 1.7 million cubic feet for rock glaciers and around 280 million cubic feet for surface glaciers. So far, researchers have identified 22 rock glaciers still active and flowing in the Teton Range. Upwards of thirty more remnant rock glaciers have been identified, no longer active, but still containing ice. Glaciers play a vital role in sustaining ecological functions, globally and locally. Their high albedo reflects solar radiation from the planet. Deglaciation and climate change are caught in a feedback loop; the loss of worldwide albedo accelerates the effects of global warming. Within Grand Teton, glaciers contribute to the region’s hydrologic regime and act as water storage reservoirs. Compared to seasonal snowpack, glacial ice contributes very little meltwater to the Tetons’ watershed. But studies in other parks have shown glaciated streams are colder than non-glaciated streams. This provides necessary refuge for cold-dependent organisms. One species of Stonefly (Lednia tetonica) finds its only home in the cold meltwater of the Teton Range. Rock glaciers are common features of montane landscapes that will likely outlast surface glaciers. Endemic alpine species will come to rely on the resilience of rock glaciers amidst a warming climate that may deplete other glacial habitats. As the entire alpine ecosystem warms, rock glaciers and their meltwater will act as a buffer, continuing to provide some of the ecosystem services of glaciated regions. All climate projections show that the Greater Yellowstone Ecosystem is transitioning from a snow-dominated to a rain-dominated ecosystem. The future will bring warmer temperatures and higher precipitation. Monitoring of the Teton glaciers will continue as a way to gauge these changes. As they recede, researchers will observe how surface glaciers evolve—potentially into more rock glaciers—and how alpine systems respond to climate change. The Teton Range is in a transitional stage of deglaciation that may differ, in timing, from other regions. The hydrologic regime is on the verge of shifting. With the accessibility of the Tetons, park researchers are in an opportune position to observe that shift. Their discoveries may extend to other regions with less accessible ranges, in various states of deglaciation For future work, the physical science team at Grand Teton National Park is collaborating with outside entities such as the Teton Alpine Stream Research (TASR) project, the USGS Benchmark Glacier Project, and universities of the mountain west. These collaborations will help regional scientists understand current trends, and how to best plan for changes to come. 
NPS ReferencesBrighenti, Hotaling, S., S. D.S. Finn, A.G. Fountain, D. Herbst, J.E. Saros, L.M. Tronstad and C.I. Millar. In press. Rock glaciers: global climate refugia for mountain biodiversity. Global Change Biology.
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Last updated: August 14, 2024