Researchers measure global ice sheets from the sky

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Two researchers from The Ohio State University recently measured the internal temperatures of the Greenland ice sheet from the sky.

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Their work explores options for how scientists gather future data to help advance climate science and further understand the movement of glacial ice around the world. 

With the help of NASA funding, Ohio State ElectroScience Laboratory Research Associates Mark Andrews and Domenic Belgiovane headed north in September 2016 to test the technology they created under the project, “UWBRAD: Ultra Wideband Software Defined Microwave Radiometer for Ice Sheet Subsurface Temperature Sensing.”

Project leader Joel Johnson, professor and chair of the Department of Electrical and Computer Engineering, said the ice sheets of Greenland and Antarctica play an important role in the global climate. Knowing the temperature of the ice at different depths is central to modeling ice sheet movement behavior.

“They contain about 70 percent of the world’s fresh water, and gauging temperatures deep beneath their surface is a critical way to predict how they might evolve in the future,” he said.

Professor Ken Jezek, a glaciology expert with Ohio State Byrd Polar Research Center, said the UWBRAD technology is “vastly more efficient” at measuring glacier subsurface temperatures over current methods, which include sending ground crews out to drill boreholes into the ice, up to a mile deep in some locations. Jezek said this drilling is not only dangerous, it's expensive, and only a few holes were ever created. Conducting ice sheet thermometry from an airplane or even a spacecraft, he said, is faster, cheaper and allows for readings over much greater geographic areas.

In this regard, the UWBRAD mission sets a new precedent.

“There is currently no way of getting temperature information below the surface,” said Andrews. “The surface temperature you can get through various means, but that doesn’t tell you much information about what is going on underneath. There hasn’t been any particular way of trying to figure that out yet from remote sensing. So, this is a first attempt at it.”

Belgiovane said his primary role on the mission involved working with project co-leader Chi-Chih Chen in the design of the antenna and assisting Andrews on the mission. He was involved in building the antenna from its initial concept and testing to its eventual flight deployment. The antenna had to withstand the rigors that come with being attached to the bottom of a DC-3 aircraft camera port in mid-flight. It did so successfully.

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The UWBRAD sensor is a specialized microwave radiometer designed to receive the naturally occurring low-frequency microwaves given off by the Earth. Because UWBRAD measures these microwaves at different frequencies, which correspond to different depths inside the ice sheet, it becomes possible to determine the temperature of ice hundreds of meters below the surface without boring holes.

“One of the ways I usually describe how the instrument works, and radiometry in general, is that literally we are looking at the world in a different light,” Andrews said. "This radiometry is an even lower frequency than infrared, that's one way to help people understand what we're looking at."

Andrews said the inspiration for UWBRAD came about because radiometers in space detected a brightness temperature anomaly over Antarctica. That anomaly lined up with the location of Lake Vostok – the largest of Antarctica’s almost 400 known lakes hidden underneath the glaciers. This discovery highlighted the potential of their work for observing features occurring beneath the ice sheet surface.

Although results appeared promising, the research mission wasn’t without its challenges. While retrieving data over Greenland the instruments shut down twice, and man-made radio frequency interference (RFI) emitting from the more heavily populated areas clouded out some results as well.

Despite the challenges, the UWBRAD team will present their data to NASA in October to see about returning to Greenland for a second attempt.

by Ryan Horns, Dept. of Electrical and Computer Engineering