The Glacier - Climate Connection
Building on the past to inform the future: The USGS Benchmark Glacier Project delivers science to a world adapting to rapid glacier loss
USGS Benchmark Glacier Project
Mountain glaciers are melting faster than the Greenland or Antarctic ice sheets ( Huggonet and others, 2021 ). This loss of ice has consequences that extend far beyond mountain landscapes, impacting ecosystems and humans on every continent. The repercussions of mountain glacier loss include changes to global sea level ( Zemp and others, 2019 ), which will cost coastal communities more than a trillion dollars by 2100 ( Neumann and others, 2015 ) and freshwater delivery to rivers and oceans , which will affect millions of people living downstream who rely on those rivers for irrigation and drinking water ( Milner and others, 2017 ).
The U.S. Geological Survey Benchmark Glacier Project is one of the longest running studies of glaciers on Earth. For over six decades, this project has coordinated intensive glacier field research to better understand the physics that control a glacier's behavior, the connections between climate and glaciers, and downstream impacts of glacier loss ( O'Neel and others, 2019 ).
Take a look at these examples of glacier change. What differences do you see?
Click and drag the center slider to reveal changes in Grinnell Glacier from 1910 to 2016 1910 (Elrod, U of M Archives) - 2016 (McKeon, USGS)
Now, at a time when glaciers are changing rapidly, the long-term data and ongoing efforts of the USGS Benchmark Glacier Project provide key scientific insight that can inform sea level and water resource management strategies.
Since the mid-1950s, the USGS Benchmark Glacier Project has documented changes at five glaciers located between 48° N in the U.S. Northern Rockies and 63° N in the Arctic.
Image: South Cascade Glacier, Sept. 2015.
Glacier change is the sum result of multiple years of response to atmospheric conditions, or climate . Each of the five mountain glaciers studied represents a distinct climate region in Western North America. This diversity allows scientists to tease apart complex regional climate conditions that impact glaciers ( O'Neel and others, 2019 ).
Image: Weather station at Wolverine Glacier measures site-specific climate parameters at regular intervals. Sept. 4, 2015.
Measurements of glacier mass balance (gain or loss of snow and ice) track seasonal and year-to-year change as each glacier responds to winter snow accumulation and summer melt. This provides a close-up look at the connection between glaciers and climate.
Image: Scientist prepares to extract a snow core on Wolverine Glacier, Sept. 2018.
Combining field measurements with remote sensing (satellite) technologies and big data processing capabilities, the project is now positioned to deliver regional estimates of glacier change.
Satellite image showing the extent of South Cascade Glacier on October 14, 2015 (cyan line) and August 8, 1958 (green line). Data from McNeil and others, 2019
Background Image: Satellite view of South Cascade Glacier terminus, Aug. 17, 2015. (@2015 DigitalGlobe Next View License)
The USGS Benchmark Glacier network is contained within North America, but findings empower scientific discovery that applies to glaciated mountain systems around the world.
Image: Scientists look for an ablation stake on Lemon Creek Glacier, Sept. 17, 2021.
Glaciers Have Far-Reaching Impacts
Glaciers are more than melting icons of climate change. What are the biological and ecological services that glaciers provide? Why is glacier loss relevant to human society?
Examples of the impacts of glacier loss at local, regional and global levels. USGS.
As reservoirs of frozen fresh water, glaciers are a key component of mountain ecosystems, sustaining species adapted to cold-water habitats ( Fell and others, 2017 ). Glaciers provide human services too, including drinking water, irrigation, hydroelectric power, and recreation ( Milner and others, 2017 ).
Examples of the connections between glaciers, ecosystems and society: (photo 1) infrastructure damage from sea level rise, (photo 2) hydroelectric power and water availability from glacial-fed reservoirs, (photo 3) recreation opportunities, (photo 4) species threatened by reduced streamflow such as Coho salmon (Oncorhynchus kisutch) , (photo 5) drinking water availability.
As climate warming speeds glacier loss, additional glacier meltwater alters the hydrologic cycle and sometimes creates environmental hazards, including outburst flooding ( Carrivick and Tweed, 2016 ). Glacier retreat has additional impacts to tourism and mountain recreation.
Mountain glacier melt contributes to changes in sea level around the world ( Zemp and others, 2019 ), impacting tens of millions of people who live along coastlines. Amplified stormsurges, high tides, coastal erosion, and wetland loss, are consequences of sea level rise.
"From Icefield to Ocean graphic" illustrates the important linkages between Alaskan glaciers and the coastal ecosystem.
Discovery Grounded in Diversity
For decades, key glaciers across western North America have been closely monitored. These consistent field measurements have provided valuable “benchmarks” to understand the linkages between glaciers and climate, ecosystem, and hydrology.
Location of the five USGS Benchmark Glaciers. Click on black pins to learn more about each glacier. ( O'Neel and others, 2019 )
USGS Glacier monitoring began with mass balance measurements at South Cascade Glacier (WA) in 1958. The project then expanded to Gulkana and Wolverine Glaciers (AK) in 1966 and Sperry Glacier (MT) in 2005. Close collaboration with the Juneau Ice Field Research Program (JIRP) yields mass balance measurements at Lemon Creek Glacier (AK) since 1953.
These five USGS Benchmark Glacier sites span mid- to high-latitudes, providing a broad sample of glacier response to climate across the continent. The sites also represent two kinds of alpine glaciers, cirque glaciers and valley glaciers, representing different stages of glacier retreat.
USGS Benchmark Glacier Tour
Click on the arrow on the right to learn about each Benchmark Glacier.
The Benchmark Glacier Project tracks glacier response to climate change across various stages of life (time) and various climate regimes (space).
Seracs (fins of ice) and crevasses (deep blue cracks) in the Wolverine Glacier icefall, June 29, 2014.
Research at the Glacier Scale
Results of glacier mass balance at the five benchmark glaciers shows a trend in glacier loss for all glaciers. USGS
The Benchmark Glaciers have been monitored for decades. To maximize the scientific value of these long-studied glaciers, the USGS Benchmark Glacier Project reanalyzed the data and consolidated field practices and data processing among the five sites in 2019. ( O'Neel and others, 2019 ).
Graphic: Cumulative mass balance (net gain or loss of snow over one year) for each USGS Benchmark Glacier. Despite occasional positive years, the overall trend indicates glacier loss for all glaciers.
Experimentation with early survey methods on these glaciers evolved into some of the standard practices used today in glaciology.
Image: Sperry Glacier at the end of the summer melt season. The ablation stake held by the researcher was placed upright through meters of snow the previous spring. The horizontal length of the stake shows how much snow and ice has melted from this site since it was placed. Sept. 26, 2021.
In addition to closely monitoring seasonal and annual changes in mass balance, these glaciers have been the hub of research focused on physical glacial processes, including how glaciers form and flow, erode rocks, influence nearby stream water, and react to changes in climate.
Image: A scientist skis to the weather station on Wolverine Glacier, Dec. 14, 2021.
For example, early research at South Cascade Glacier contributed to the understanding of how water flows through snow and under the glacier ( Fountain and Walder, 1998 ).
Image: Tracer is added to glacier runoff to document sub-glacial flow on Wolverine Glacier, Aug. 17, 2016.
Ongoing Glacier Scale Research
Maintaining the Mass Balance Record
Direct measurement of mass balance at the five benchmark glaciers track the annual cycle of accumulation and loss across the glacier surface, essentially taking the pulse of the glacier’s health.
Collection of mass balance data includes: (photo 1) scientist locates and records snow level on ablation stake, (photo 2) snow pit is dug to the glacier surface and sampled from top to bottom, (photo 3) wedge-cutter samples from snow pit are weighed to obtain snow density, (photo 4) results are recorded in field notebook, (photo 5) snow corer is used to obtain snow samples as an alternative to digging a snow pit, (photo 6) snow core samples are cut in sections to weigh to obtain snow density, (photo 7) layers within snow core samples are measured and recorded.
Maintaining the Benchmark Glacier Project involves visiting each glacier twice every year, to measure snow depth and density in the spring, and to measure melt in the fall, across each glacier’s elevation range.
This work requires scientists skilled in glacier travel. Site visits are labor-intensive, but provide a detailed record of each glacier’s response to climate and geographic factors that that cannot be replaced by remote sensing or modeling approaches to understanding glacier behavior.
Image: Scientists record snow density measurements at a snow pit on Gulkana Glacier, April 30, 2020.
Use of identical methods across all USGS Benchmark Glacier sites allows for the comparison of apples to apples across the different glacier settings.
Video: Scientists use a wedge cutter to collect snow samples on Gulkana Glacier. Each sample is weighed to determine the density of the snowpack on the glacier, a necessary measurement for calculating mass balance. April 4, 2019, USGS.
Climate Connections
High elevation weather stations are maintained near the glacier margins. They provide complementary weather data to assess how local climate influences glacier change.
Image: USGS scientist adds new sensors to the weather station on Gulkana Glacier, April 30, 2020.
Firn Evolution
To calculate glacier mass balance, scientists must know the density of snow and ice. However, glaciers are comprised of not only ice, which has a known density, and snow, which has density that can vary, but also firn, which is the transitional material between snow on the surface and the glacier ice below. Firn density is less than that of glacier ice, but more than that of snow. Furthermore, the thickness of the firn layer varies across the glacier. Scientists with the USGS Benchmark Glacier Project are working to understand the density of firn, the final puzzle piece needed to provide the best estimate of mass balance possible.
Image: Layers within a segment of a Wolverine Glacier snow core show how density varies in the snow. May 13, 2016.
USGS scientists measure firn density and track the thickness of firn below the glacier surface. Additional instrumentation tracks the temperature of the firn throughout the year and is used to understand the evolution of firn density through compaction and potential freezing of surface melt water.
Image: A snow core is weighed and measured to support firn evolution studies on Wolverine Glacier, Sept. 2018 .
Refining mass balance calibration
At Wolverine Glacier, scientists are quantifying mass balance with geophysical techniques, including ground penetrating radar ( GPR ) and LiDAR data collected during intensive field campaigns. While not feasible to undertake each year or at regional scale, the data is used to provide corroborating information on snow accumulation and ice melt, to complement mass balance estimates derived from the traditional stake method.
Image: Scientists set up ground penetrating radar equipment on Wolverine Glacier, April 23, 2015.
Such analysis helps scientists refine their methods to continually improve the accuracy and understand the uncertainties of their mass balance estimates, which are crucial to translating these data on glacier loss into actionable information for water resource management.
Image: Scientist takes a repeat phase-sensitive radio-echo-sounding system measurement to study firn compaction, May 24, 2021.
Time lapse video showing the installation of ablation stakes using a steam drill at South Cascade Glacier, June 16,2022.
(Including some interesting ice worm activity in the foreground!)
Research at the Regional Scale
In the past, state of the art technology was limited to direct glaciological measurements – digging snow pits and installing ablation stakes – and using surveyor's tools. Technological advances over the ensuing decades provide an assortment of techniques which broaden the project’s perspective.
Image: Long measurement poles are used to probe snow depth around an ablation stake on Wolverine Glacier, June 3, 2016.
High-resolution photographs taken from satellites in space (a type of remote sensing ) and methods for generating regional elevation maps (digital elevation models) enable comprehensive ice elevation surveys and calculation of glacier volume change. By comparing glacier surface elevation between different years, scientists determine the loss of water in relation to climate records, linking climate to glacier change across regional scales.
Image: Satellite image of glaciers near the central region of Glacier National Park, MT. USDA image, August 27, 2005.
Ongoing Regional Scale Research
Regional Analysis
Using repeat imagery from satellites and aircraft, scientists are analyzing glacier change across Glacier National Park (GNP), Montana. This effort will help resource managers plan for ecosystem and hydrologic changes in this UNESCO World Heritage Site . Scientists will then scale up, applying techniques honed for GNP, to analyze regional glacier change in the Pacific Northwest (PNW) and Alaska.
Image: Glacier margin perimeter and area are determined by aerial photo analysis. Historic (1966) and contemporary (2015) images of Grinnell Glacier, GNP, show how the glacier shape and size have changed. USGS Data
Contributing to Global Studies
South Cascade, Gulkana, Wolverine and Lemon Creek Glaciers have the longest continuous mass balance records in the United States and are among the 40 longest in the world. As world ‘reference’ glaciers, they are among the sites included in the World Glacier Monitoring Service’s internationally coordinated glacier monitoring network , which tracks global glacier change as a resource for the Intergovernmental Panel on Climate Change (IPCC) and climate scientists across the globe. Tracking these glaciers for decades has helped scientists unravel how glaciers respond to climate, which in turn helps policy makers prepare for glacier loss as the climate continues to warm.
Images: The USGS Benchmark Glacier Project advances the understanding of the climate - glacier connection as it applies to mountain glaciers around the world. (photo 1) Scientist carrying a steam drill, en-route to install a new ablation wire on Wolverine Glacier, Sept. 7, 2018, (photo 2) Alpinglow on peaks surrounding Wolverine Glacier, Dec. 21, 2021, (photo 3) Scientist measuring ablation wire on Wolverine Glacier, Sept. 7, 2018. USGS images
Decades of Discovery
Since benchmark glacier monitoring began in 1958, these glaciers have been a hub of field research, yielding hundreds of scientific publications relating to how glaciers work and how glaciers are impacted by climate.
In particular, a reanalysis of benchmark glacier data between 1983-2017 ( O’Neel and others, 2019 ) provides insight regarding how climate and regional factors influence glacier change:
- All five Benchmark glaciers lost ice mass since the start of measurements
- Increased summer warming is the primary cause of glacier loss
- Elevation, shading, wind, avalanches, and glacier surface features influence melt rates
- Preexisting ice thickness and distribution of ice across elevation control glacier retreat
- Continentality (distance from the coast) impacts glacier loss more than latitude
Informing the Future
Image: Scientist holds ablation stakes used to measure the change in snow depth on Gulkana Glacier, April 25, 2019.
Continuous research endeavors lasting decades such as the USGS Benchmark Glacier Project are rare. The project’s value has been newly invigorated by the imperative to understand the physics that control glacier response to climate in our warming world. Researchers have honed glaciological methods to track the changing benchmark glaciers with consistent field measurements and produce intercomparable results. Innovation in remote sensing techniques have broadened the project’s scope by providing the means to calculate glacier change across regions, leading to improved understanding of the utility of the benchmark glacier datasets in regional assessments of changes. Sixty years into its history, this project will continue its monitoring legacy to reveal the physics that govern glacier response to climate and the resultant downstream impacts of glacier change. This information will provide resources managers and decision-makers what they need when considering the ecologically important resource of dynamic ice.
Click and drag the center slider to reveal changes from 1908 to 2015 at Sperry Glacier, one of the USGS Benchmark Glaciers 1908 (Leibig, GNP Arvchives) - 2015 (Clark, USGS)
Resources
USGS Glacier Websites
USGS Glacier Factsheets
Outside Resources
Resources for Educators
Photo comparison shows mass loss during the first 49 years of the Benchmark Glacier Project at Gulkana Glacier.
All photographs by U.S. Geological Survey unless otherwise noted
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