As warming atmospheric temperatures cause glaciers to thin and retreat around the world, understanding how glaciers respond to climate change, algae growth and impurities such as dust and black carbon is vital. Understanding the response helps scientists, policymakers and communities to mitigate damage and protect watersheds and communities that depend on these glaciers. However, many glaciers are located in remote locations that are difficult to access and difficult to study.
In a paper published in the Journal of Glaciology in May 2022, physicist Markus Allgaier collaborated with geologists and geographers to develop a portable instrument that could be easily placed in a backpack and carried to remote glaciers to measure the optical properties and composition of their ice.
Collecting data on ice composition and glacier retreat is important to evaluate how glaciers respond to climate change. The data also helps scientists predict how communities downstream of the glaciers might be affected by their retreat. Currently, many glaciologists rely on modeling techniques to evaluate the ice composition of glaciers, especially for more remote glaciers that are difficult to access and difficult to investigate.
However, without being on the glacier, it can be difficult to accurately measure ice composition, algae growth, and dust and black carbon levels. This deficiency makes backpack glaciology — hiking to remote locations with portable equipment for physical measurements on the glaciers — vital to understanding the ice and its behavior.
Backpack glaciology comes with a tradeoff, however. To make instruments portable, they are often simple and unable to measure variables such as albedo, which is important to understand retreat. For example, the North Cascades Glacier Climate Project, a decades-long project to measure glaciers in northwest Washington, uses a long metal probe with detachable segments, a laser rangefinder and marked ropes to conduct most of its research. These tools help researchers collect vital data on snow depth, ablation rates, endpoint location and glacier profiles, but scientists looking to measure albedo or ice composition on remote glaciers have few choices available.
Allgaier, a postdoctoral physicist at the University of Oregon, is working to address the lack of options and improve the measurement tools available to glaciologists around the world. Allgaier explained in an interview with GlacierHub that while he has a background in quantum physics, he wanted to “apply these fields to environmental science and climate research,” citing his love of mountains and his desire to contribute to research that focuses on on understanding it. He started by researching what optical measurements glaciologists use and thinking about how they could be improved and what was missing from the techniques used today. He engaged glaciologists, geographers and hydrologists to develop an instrument together.
These collaborations culminated in the development of a device that measures the composition and structure of glacial ice using photons or subatomic light particles. The device shoots a laser pulse into the glacial ice and measures the time it takes for the photons to bounce off the ice and hit a receiver about two meters away. Air bubbles in the glacier scatter the laser pulse in random directions, changing both the time it takes to hit the receiver and the shape of the pulse when it gets there.
According to Allgaier, “the pulse shape and duration of the detected light is unique, and these tell us how much light is absorbed in the ice and how much scattering there is.” In turn, this data allows researchers to determine the composition and density of the ice, as well as the optical properties of the glaciers. These can be used to predict the withdrawal rate.
Stressing the importance of this device to both large and small glaciers, Allgaier said that by measuring the composition and structure of the ice, the device “gives a glimpse of what causes melting and why the glacier albedo is what it is.”
While this device is perfect for collecting data on difficult-to-access glaciers, it can also be used to verify that remote-sensing data from easily accessible glaciers is accurate and matches what is found on the ground. The latter idea arose from Allgaier’s collaboration with geographers at the University of Oregon. Johnny Ryan, an assistant professor in the geography department, participated in the project to provide perspective on glaciers, ice sheets and practical applications of the device. Ryan says he and his colleagues in the geography department were able to offer suggestions on how to improve the device to work best in the field and provide insight into how the project might fit into current glaciological research.
According to Ryan, the geographers were also instrumental in testing the laser in the field — they knew where to go and how to navigate the glaciers and how to get permits. The group tried it out on a few Oregon glaciers: the Crook Glacier on Broken Top Mountain and the Collier Glacier on the North Sister. Both tests were successful.
So far, only a small fraction of the world’s glaciers have been studied, Ryan said. In the future, this tool will help researchers to “study glaciers that have not normally been studied, but are still important for water resources and sea level rise.” And by verifying data from satellites and aircraft, this new research is especially important for communities downstream of glaciers nestled in mountains too dangerous to climb. Understanding how their glaciers are changing and receding is vital to the future of these communities.
Researchers use lasers to get a new look at Oregon’s glaciers
Markus Allgaier et al, Direct measurement of optical properties of glacial ice using a photon counting diffuse LiDAR, Journal of Glaciology (2022). DOI: 10.117/jog.2022.34
Provided by State of the Planet
Quote: New tool helps researchers study remote glaciers (2022, October 19) retrieved October 19, 2022 from https://phys.org/news/2022-10-tool-remote-glaciers.html
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