LAWRENCE — A team of researchers with the Center for Remote Sensing of Ice Sheets (CReSIS) at the University of Kansas will soon have better ways to monitor and predict the impact of climate change on polar ice sheets.
Rick Hale, associate professor of aerospace engineering at the KU School of Engineering, and his collaborators received a $1.7 million dollar, three-year grant from the National Science Foundation to develop enhanced radar capable of capturing higher-resolution images of polar ice sheets, in a more thorough and efficient manner.
"This new ultra-wideband radar merges two functionalities. You get the deep ice sounding capability that provides details on the bed conditions, and you have the increased bandwidth of the accumulation radar, which provides data on the conditions of the layers within the first few hundred meters of the ice sheet," Hale said.
This setup will improve current research methods, which involve attaching separate radars operating at different wavelengths and bandwidths to an aircraft. After data are collected from these multiple instruments, researchers must then go through the painstaking process of synchronizing the data from the individual radars to get a complete picture of the ice layers and ice bed. Combining a low-operating frequency to enable penetration depth to detect bedrock through thick ice with the ultrawide bandwidth to provide high resolution layering from the surface to the bed provides the greatest flexibility to science teams in the field.
"The new system will provide more immediate wide-swath images of the ice bed interface and map the internal layering of the ice sheet, through 2.5 miles of ice, all the way from the surface to the bed, with a single system, and without sacrificing either penetration depth or resolution. That's a significant advantage," Hale said. "With the wide-swath imaging capability enabled by the large-antenna array and advanced radars, we can fly more sparse lines with the aircraft but still get the fine resolution at the bed."
Each layer of an ice sheet provides a historical record of the climate conditions at a certain time. Researchers drill through the glacier and gather a physical sample of ice in order to analyze changes over thousands of years. This process provides a physical validation of the digital images captured by the radar systems designed by KU.
Images collected from KU's radar help researchers decide where to drill for their ice core samples. A site must be chosen that provides a pure record of annual snowfall – where layers have not mixed over time. The presence of water at the bedrock, or even ice that's softened from being near water at the bedrock, can lead to layers mixing and interfere with data collection.
"With all of the physics-based computer models, it's the boundary conditions that are important. The simulation tools have improved, but any simulation is subject to the boundary conditions that you put on the tool, and we still don't know what the boundary conditions are for some of these fast-moving outlet glaciers," Hale said. "We're certainly not seeing the conditions at the ice bed at the resolution that we need and this sensor would allow that."
The critical boundary conditions for any ice-sheet model are: (1) the surface topography of the ice sheet; (2) the shape of the bedrock beneath the ice; (3) the surface mass balance; (4) the internal temperature profile; and (5) whether there is water at the bed. The surface and bed topographies are perhaps the most critical, since they determine the most important input into any ice-sheet model, the driving stress. Water at the bed is also important because it promotes sliding, which causes ice streams to speed up.
The development of the new radar will be aided by laboratories within KU's new Measurement, Materials and Sustainable Environment Center, including an anechoic chamber that is used to fine tune antennas and radar signals, and the composite materials lab, which provides ample space to design and assemble the necessary components.
The project involves international collaborations with the Niels Bohr Institute, Centre of Excellence for Ice and Climate at the University of Copenhagen, Denmark, the Greenland Nature Institute and Germany's Alfred Wegener Institute (AWI) for Polar and Marine Research, strengthening KU's role in Sustaining the Planet, Powering the World. Additional negotiations are in progress wherein AWI will provide additional funds to duplicate a set of radars for their aircraft and provide aircraft flight hours to test and verify systems function as designed. "This grant and the ongoing breakthrough research by the CReSIS team demonstrates that this is truly a world class center," said Stan Rolfe, interim dean of engineering. "It is wonderful to see KU play such a key role in working to solve the challenges posed by global change."