A Mobile, Multichannel, UWB Radar for Potential Ice Core Drill Site Identification in East Antarctica: Development and First Results

Abstract

We developed a high-performance, multi-channel, ultra-wideband radar system for measurements of the base and interior of the East Antarctic Ice Sheet. We designed the radar to be high-power (4,000 W peak) yet portable and operate with 60-MHz bandwidth at a center frequency of 200 MHz, providing high sensitivity and fine vertical resolution relative to current technology. We used the radar to perform extensive measurements as a part of a multinational collaboration. We collected data onboard a tracked vehicle outfitted with an array of high-gain antennas. We sounded 2-km to 3-km thick ice near Dome Fuji. Preliminary ice thickness data match those obtained via semicoincident measurements performed with a different surfacebased pulse-modulated radar system operated during the same field campaign, as well as previous airborne measurements. In addition, we mapped internal reflection horizons with fine vertical resolution from 300 m below the ice surface to ~100 m above the bed. In this paper, we provide a detailed overview of the radar instrument design, implementation, and field measurement setup. We present sample data to illustrate its capabilities; and discuss how the data collected with it will be valuable for the assessment of promising drilling sites to recover ice cores 0.9 to 1.5 million years old. Index Terms-Oldest ice core, UWB radar sounding. I. INTRODUCTION eep ice cores from the Antarctic Ice Sheet provide a detailed record of climate state changes, volcanic and solar activity, as well as atmospheric composition dating back 800,000 years (800 ka) [1-2]. Unsolved scientific questions related to the role of atmospheric greenhouse gases on the Mid-Pleistocene transition (MPT) [3], which appears to have occurred between ~900 ka and 1.2 Ma, have prompted the international scientific community in a quest for suitable drilling locations to recover samples of the Oldest Ice that will

High-resolution subglacial topography around Dome Fuji, Antarctica, based on ground-based radar surveys conducted over 30 years

“…Even though such vertically long antennae would have difficulty in mounting on ground-based platforms, they provide an important opportunity for improving conventional radar systems. Modern radar sounders with phase analysis and SAR processing (e.g., Rodriguez-Morales et al, 2020;Lilien et al, 2021) are able to remove hyperbolic effects. For improving the accuracy of bedrock topography measurements, we can apply radar with high-gain and high-directivity antennae, state-of-the-art modern radar with focused SAR processing, or both.…”

“…In the present study, we focus on the performance of the conventional JARE pulse-modulated radar. Ice thickness detected with the wideband radar sounder provided by the Center for Remote Sensing of Ice Sheets (CReSIS), the University of Kansas, is discussed elsewhere (Rodriguez-Morales et al, 2020).…”

“…These authors suggested primary areas for potential drilling sites on the subglacial mountains based on the distinction of melted/frozen bottom by ice sheet modelling under the assumption of surface mass balance and geothermal heat flux. Detailed basal topography data with higher spatial resolution are essential to provide further constraints for modelling to improve the site predictions because actual bed topography has much finer-scale (i.e., < 10 km) mountainous undulations (e.g., Fujita et al, 1999Fujita et al, , 2012Karlsson et al, 2018;Rodriguez-Morales et al, 2020). New ice-penetrating radar surveys with high spatial resolution and the compilation with existing data have been necessary to improve the ice thickness maps, which would facilitate the identification of candidate sites for the oldest ice drilling.…”

“…The hyperbolic effects mask sharp peaks and steep valleys near such peaks, resulting in underestimation of ice thickness. Focused synthetic aperture radar (SAR) processing can be used to correct the errors (e.g., Young et al, 2017;Rodriguez-Morales et al, 2020). Another approach is to make the footprint of the radar beam smaller with conventional radar soundings.…”

Comment on tc-2021-266

“…The hyperbolic effects mask sharp peaks and steep valleys near such peaks, resulting in underestimation of ice thickness. Focused synthetic aperture radar (SAR) processing can be used to correct the errors (e.g., Young et al, 2017;Rodriguez-Morales et al, 2020). Another approach is to make the footprint of the radar beam smaller with conventional radar soundings.…”