An Airborne Radar Sounding Instrument Concept for Characterizing Water Storage in Greenland's Porous Ice and Firn
Abstract
Meltwater runoff is a significant contributor to mass loss in Greenland and therefore to sea level rise. Regional climate and surface mass balance models assume efficient delivery to the ocean; however, ground-based studies suggest extensive meltwater storage in porous firn aquifers and potentially in weathered ice in the ablation zone which can significantly delay runoff. Constraining the spatial extent and water storage capacity of these areas would inform understanding of the hydrologic processes governing supraglacial runoff, as well as mass balance models.
Airborne radar sounders are well suited to extensive geophysical surveys. However, current systems are responsive primarily to reflecting interfaces and are typically designed to suppress returns from volume scattering phenomena such as water-filled pores. Therefore, we explore the design requirements for an airborne radar sounding system which can constrain the size and density of water-filled pores in the upper 50 meters of the ice sheet based on volumetric backscatter power. We employ a Mie scattering model to identify a series of resonant frequencies which correspond to high backscatter from pores of specific radii. On this basis, we present a multi-frequency, dual-polarization instrument concept that employs interleaved pulses at these resonant frequencies to constrain pore size and measures backscattered power to derive pore density. Additionally, we develop requirements for the radar system parameters (power, pulse repetition frequency, resolution, etc) as well as the antenna and digital system components needed to make these measurements. Our results support the feasibility of investigating porous water storage using radar sounding systems, albeit requiring a highly tuned design to achieve good performance.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C51F1125C
- Keywords:
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- 0768 Thermal regime;
- CRYOSPHEREDE: 0770 Properties;
- CRYOSPHEREDE: 0776 Glaciology;
- CRYOSPHEREDE: 0794 Instruments and techniques;
- CRYOSPHERE