Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 4.524 IF 4.524
  • IF 5-year value: 5.558 IF 5-year 5.558
  • CiteScore value: 4.84 CiteScore 4.84
  • SNIP value: 1.425 SNIP 1.425
  • SJR value: 3.034 SJR 3.034
  • IPP value: 4.65 IPP 4.65
  • h5-index value: 52 h5-index 52
  • Scimago H index value: 55 Scimago H index 55
Volume 12, issue 8 | Copyright
The Cryosphere, 12, 2689-2705, 2018
https://doi.org/10.5194/tc-12-2689-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 16 Aug 2018

Research article | 16 Aug 2018

Multi-channel and multi-polarization radar measurements around the NEEM site

Jilu Li1, Jose A. Vélez González1, Carl Leuschen1, Ayyangar Harish2, Prasad Gogineni3, Maurine Montagnat4, Ilka Weikusat5, Fernando Rodriguez-Morales1, and John Paden1 Jilu Li et al.
  • 1Center for Remote Sensing of Ice Sheets, University of Kansas, Lawrence, Kansas 66045, USA
  • 2Department of Electrical Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India
  • 3Department of Electrical and Computer Engineering, University of Alabama, Tuscaloosa, Alabama 35487, USA
  • 4IGE, Université Grenoble Alpes, CNRS, IRD, G-INP, 38041 Grenoble, France
  • 5Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 24, 27568 Bremerhaven, Germany

Abstract. Ice properties inferred from multi-polarization measurements, such as birefringence and crystal orientation fabric (COF), can provide insight into ice strain, viscosity, and ice flow. In 2008, the Center for Remote Sensing of Ice Sheets (CReSIS) used a ground-based VHF (very high frequency) radar to take multi-channel and multi-polarization measurements around the NEEM (North Greenland Eemian Ice Drilling) site. The system operated with 30MHz bandwidth at a center frequency of 150MHz. This paper describes the radar system, antenna configurations, data collection, and processing and analysis of this data set. Within the framework derived from uniaxial ice crystal model, we found that ice birefringence dominates the power variation patterns of co-polarization and cross-polarization measurements in the area of 100km2 around the ice core site. The phase shift between ordinary and extraordinary waves increases nonlinearly with depth. The ice optic axis lies in planes that are close to the vertical plane and perpendicular or parallel to the ice divide depending on depth. The ice optic axis has an average tilt angle of about 11.6° vertically, and its plane may rotate either clockwise or counterclockwise by about 10° across the 100km2 area, and at a specific location the plane may rotate slightly counterclockwise as depth increases. Comparisons between the radar observations, simulations, and ice core fabric data are in very good agreement. We calculated the effective colatitude at different depths by using azimuth and colatitude measurements of the c axis of ice crystals. We obtained an average effective c axis tilt angle of 9.6° from the vertical axis, very comparable to the average optic axis tilt angle estimated from radar polarization measurements. The comparisons give us confidence in applying this polarimetric radio echo sounding technique to infer profiles of ice fabric in locations where there are no ice core measurements.

Publications Copernicus
Download
Short summary
Ice properties inferred from multi-polarization measurements can provide insight into ice strain, viscosity, and ice flow. The Center for Remote Sensing of Ice Sheets used a ground-based radar for multi-channel and multi-polarization measurements at the NEEM site. This paper describes the radar system, antenna configurations, data collection, and processing and analysis of this data set. Comparisons between the radar observations, simulations, and ice core fabric data are in very good agreement.
Ice properties inferred from multi-polarization measurements can provide insight into ice...
Citation
Share