UHF Radar Sounding of Polar Ice Sheets

Abstract

In this letter, we report on the design, development, and field operation of a surface-based multi-channel ultrawideband (UWB) ultrahigh frequency (UHF) radar to measure ice thickness, basal conditions, and ice-shelf bottom melt rates. The radar concept is based on the recent success in sounding shallow low-loss ice (~1 km) and measuring the ice-shelf melt rates with a 600–900-MHz low-power radar, referred to as the accumulation radar. Our proposed radar system operates over the same frequency band, from 600 to 900 MHz, with a peak transmit power of 800 W. We used a large and lightweight 16 m $\times17$ m antenna array arranged in a Mills cross-configuration to obtain the required radar sensitivity to sound more than 3-km-thick ice and image the internal layers at a fine vertical resolution of about 60 cm. We used the system at the East Greenland Ice-coring Project (EGRIP) site in Summer 2018 to collect data over ~100 km of lines. We sounded about 2.8-km-thick ice with more than 40-dB signal-to-noise ratio and mapped the internal layers to a depth of almost 2.5 km. Our results show that an airborne or spaceborne radar operating at frequencies as high as 900 MHz with a large antenna array can be used to map large ice sheets in Greenland and Antarctica.