Tucson Standard

A University of Arizona-led project that uses advanced airborne radar mounted on low-flying aircraft to study Arctic glaciers is one of six new missions to receive funding from NASA. Dubbed Snow4Flow, the mission is led by Jack Holt, a professor in the UArizona Lunar and Planetary Laboratory and the Department of Geosciences. It is one of only two missions selected from 42 proposals to be funded at $30 million. Four other projects will each receive $15 million.

The funding, announced April 19, comes from NASA's Earth Venture program, which focuses on missions that use instruments mounted on aircraft to make measurements that cannot be made from space.

Snow4Flow aims to better understand the snowfall feeding into glaciers and how fast those glaciers move. In combination with climate models, this will allow researchers to make more accurate predictions about how glaciers shrink and grow and how much they contribute to sea level change, Holt said.

"Those glaciers are retreating fast, and they're making a large contribution to sea level rise, but we don't know exactly how much and how that's going to change in the future," he said. "Right now, we can't accurately measure how much snow feeds into the glacier systems, and without knowing their ice thickness, you don't know the volume of ice flowing out from the glacier. Those are things that you can't measure with satellites from space."

Snow4Flow addresses a critical need for climate scientists in developing accurate projections of sea level rise from melting land glaciers. Across four major study regions representing many hundreds of glaciers in the Northern Hemisphere – Alaska/Yukon, southeastern Greenland, the Canadian Arctic Archipelago, and Svalbard archipelago in Norway – the Snow4Flow team will use microwave and long-wavelength radar sounders mounted on low-flying aircraft to measure snow accumulation and glacial ice thickness. The resulting data will inform models of glacier dynamics and their contributions to sea level rise.

While Holt's team will focus on studying glaciers in the Northern Hemisphere, they expect the data collected over the five-year project will be applicable to glaciers in other parts of the world. The measurements can be used to calibrate observations from different satellite missions, allowing scientists to monitor glaciers from space and improve models predicting how glaciers globally will respond to climate change.

Snow4Flow centers around two instruments: one with low-frequency radar generating very long wavelengths needed to penetrate thick ice sheets and another operating at shorter wavelengths optimized for probing blankets of snow.

"We will mount them on small aircraft – fixed-wing or helicopters or both – which will fly low over glaciers that pass through mountain valleys," Holt said. "During those flights, we will collect data that essentially produce cross-sections of the snow and glacier ice thickness."

"At the same time, these missions improve our ability to use satellites by calibrating algorithms that attempt to use spaceborne data for such purposes," he added.

Rather than having science and instrument teams defined at proposal time, projects selected for NASA funding will be open to other scientists interested in joining. Holt expects a final team assembled by fall 2025 with flight operations beginning in spring 2026. The mission will take place over three years, capturing winter snowfall before snowmelt begins in summer months.

Holt attributes Snow4Flow's success in attracting federal funding partly due to a strategic cluster hire at UArizona including Ali Behrangi in Hydrology and Atmospheric Sciences and Chris Harig in Geosciences through UArizona's Earth Dynamics Observatory (EDO). Cluster hires recruit multiple scholars into departments based on shared research interests. Behrangi studies snowfall in high-latitude regions while Harig studies ice mass loss using gravity measurements from space satellites.

"The University of Arizona's continued success in attracting this level of research funding is a direct consequence of our efforts focusing recruitment in key areas where we offer unparalleled expertise," said University President Robert C. Robbins. "Snow4Flow exemplifies an opportunity where our researchers can assemble a dream team capable of developing solutions for some pressing challenges."

UArizona’s EDO combines strengths in space exploration, instrumentation, and Earth sciences for learning more about our planet. Collecting information about Earth from space provides new insights into how Earth systems work, their changes over time, and human responses.

Behrangi noted EDO played a crucial role by encouraging innovative thinking: "It allowed us to break free from conventional ideas envisioning a broader mission instead of smaller proposals."

"These large federal programs are increasingly interdisciplinary," said Harig. "Jack (Holt) used our expertise within EDO refining the project idea over years positioning it well when solicitation came out."