29 Jul 2022
 | 29 Jul 2022
Status: a revised version of this preprint is currently under review for the journal TC.

Wind Transport of Snow Impacts Ka- and Ku-band Radar Signatures on Arctic Sea Ice

Vishnu Nandan, Rosemary Willatt, Robbie Mallett, Julienne Stroeve, Torsten Geldsetzer, Randall Scharien, Rasmus Tonboe, Jack Landy, David Clemens-Sewall, Arttu Jutila, David N. Wagner, Daniela Krampe, Marcus Huntemann, John Yackel, Mallik Mahmud, David Jensen, Thomas Newman, Stefan Hendricks, Gunnar Spreen, Amy Macfarlane, Martin Schneebeli, James Mead, Robert Ricker, Michael Gallagher, Claude Duguay, Ian Raphael, Chris Polashenski, Michel Tsamados, Ilkka Matero, and Mario Hoppman

Abstract. Wind transport alters the snow topography and microstructure on sea ice through snow redistribution controlled by deposition and erosion. The impact of these processes on radar signatures is poorly understood. Here, we examine the effects of snow redistribution on Arctic sea ice from Ka- and Ku-band radar signatures. Measurements were obtained during two wind events in November 2019 during the MOSAiC expedition. During both events, changes in Ka- and Ku-band radar waveforms and backscatter coincident with surface height changes measured from a terrestrial laser scanner are observed. At both frequencies, snow redistribution events increased the dominance of the air/snow interface at nadir as the dominant radar scattering surface, due to wind densifying the snow surface and uppermost layers. The radar waveform data also detect the presence of previous air/snow interfaces, buried beneath newly deposited snow. The additional scattering from previous air/snow interfaces could therefore affect the range retrieved from Ka- and Ku-band satellite radar altimeters. The relative scattering contribution of the air/snow interface decreases, and the snow/sea ice interface increases with increasing incidence angles. Relative to pre-wind conditions, azimuthally averaged backscatter at nadir during the wind events increases by up to 8 dB (Ka-band) and 5 dB (Ku-band). Binned backscatter within 5° azimuth bins reveals substantial backscatter variability in the radar footprint at all incidence angles and polarizations. The sensitivity of the co-polarized phase difference is linked to changes in snow settling and temperature-gradient induced grain metamorphism, demonstrating the potential of the radar to discriminate between newly deposited and older snow on sea ice. Our results reveal the importance of wind, through its geophysical impact on Ka- and Ku-band radar signatures of snow on sea ice and has implications for reliable interpretation of airborne and satellite radar measurements of snow-covered sea ice.

Vishnu Nandan et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on tc-2022-116', Andrew Shepherd, 01 Aug 2022
  • RC1: 'Comment on tc-2022-116', Nathan Kurtz, 30 Aug 2022
  • RC2: 'Comment on tc-2022-116', Silvan Leinss, 05 Sep 2022
    • AC2: 'Reply on RC2', Vishnu Nandan, 08 Jan 2023
      • AC3: 'Reply on AC2', Vishnu Nandan, 09 Jan 2023

Vishnu Nandan et al.

Video supplement

Supplemental Video 2: Ranging Analysis of KuKa Radar on snow-covered Arctic sea ice during MOSAiC Expedition Willatt, Rosemary; Clemens-Sewall, David

Supplemental Video 1: CCTV Footage of the remote sensing footprint between 9 and 16 November 2019 from the MOSAiC Expedition Spreen, Gunnar; Huntemann, Marcus

Vishnu Nandan et al.


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Short summary
We show that, wind blows and redistributes snow on sea ice, and Ka- and Ku-band radar signatures detect both newly deposited and buried snow layers that can critically affect snow depth measurements on ice. Radar measurements, meteorological and snow physical data were collected during the MOSAiC Expedition. With frequent occurrence of storms in the Arctic, our results provide baseline information that are vitally important for accurately calculating snow depth on sea ice from satellite radars.