New radar tech discovers Earth's hidden ice — preps to explore life on Europa

The research team conducted surveys over the Devon Ice Cap in the Canadian Arctic to test the technique. They successfully mapped a layer of impermeable ice near the surface, resembling a slab, which redirects surface melt into water channels downhill. 

This finding, as highlighted by Kristian Chan, a graduate student involved in the study, can aid in predicting the future of the ice cap and its contribution to rising sea levels.

"If you have only relatively thin ice layers, then the firn [snow-packed surface layers] has the ability to absorb and retain surface meltwater," Chan said. "But if these impermeable slabs are widespread, then the contribution of surface melt to sea level rise is enhanced," he explained in a press release. 

The ice layers on the Devon Ice Cap were unexpectedly thick, with some forming slabs up to 16 feet thick over several miles. 

These slabs effectively pool and redirect meltwater, as confirmed by correlating the locations of the thickest ice slabs with those of meltwater rivers. The study demonstrates the potential of the new radar technique in revealing such insights.

Chan and the UTIG team, led by Senior Research Scientist Don Blankenship, are developing a radar instrument called REASON, set to launch aboard NASA's Europa Clipper in 2024. This mission and a European Space Agency spacecraft launched earlier will enable two ice-penetrating radar instruments to investigate Jupiter's moons Europa and Ganymede. 

Significantly, both radar systems are compatible with Chan's technique.

The newfound capability will allow scientists to explore the upper layers of icy shells, potentially uncovering frozen brine, cryovolcanic remnants, or plume fallout deposits. 

These findings hold significant importance as they may provide clues about habitable environments or even serve as potential habitats in subsurface regions, as explained by coauthor Cyril Grima, a UTIG researcher and radar expert who is also part of the REASON team.

"Kristian has given us the ability to see things hidden just beneath the surface that is potentially accessible to future landers," Grima added. "It's really improved the reconnaissance ability of our radar instruments."

The full study was published in TheCryosphereand can be found here.

Study abstract:

Melting and refreezing processes in the firn of the Devon Ice Cap control meltwater infiltration and runoff across the ice cap, but their full spatial extent and effect on near-surface structure is difficult to measure with surface-based traverses or existing satellite remote sensing. Here, we derive the coherent component of the near-surface return from airborne ice-penetrating radar surveys over the Devon Ice Cap, Canadian Arctic, to characterize firn containing centimeter- to meter-thick ice layers (i.e., ice slabs) formed from refrozen meltwater in firn. We assess the use of dual-frequency airborne ice-penetrating radar to characterize the spatial and vertical near-surface structure of the Devon Ice Cap by leveraging differences in range resolution of the radar systems. Comparison with reflectivities using a thin layer reflectivity model, informed by surface-based radar and firn core measurements, indicates that the coherent component is sensitive to the near-surface firn structure composed of quasi-specular ice and firn layers, limited by the bandwidth-constrained radar range resolution. Our results suggest that average ice slab thickness throughout the Devon Ice Cap percolation zone ranges from 4.2 to 5.6 m. This implies conditions that can enable lateral meltwater runoff and potentially contribute to the total surface runoff routed through supraglacial rivers down glacier. Together with the incoherent component of the surface return previously studied, our dual-frequency approach provides an alternative method for characterizing bulk firn properties, particularly where high-resolution radar data are not available.