29 Jul 2022
29 Jul 2022
Status: 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 Nandan1,2, Rosemary Willatt3, Robbie Mallett3, Julienne Stroeve1,3, Torsten Geldsetzer2, Randall Scharien4, Rasmus Tonboe5, Jack Landy6, David Clemens-Sewall7, Arttu Jutila8, David N. Wagner9,10, Daniela Krampe8, Marcus Huntemann11, John Yackel2, Mallik Mahmud2, David Jensen1, Thomas Newman3, Stefan Hendricks8, Gunnar Spreen11, Amy Macfarlane9, Martin Schneebeli9, James Mead12, Robert Ricker13, Michael Gallagher14, Claude Duguay15,16, Ian Raphael7, Chris Polashenski7, Michel Tsamados3, Ilkka Matero8, and Mario Hoppman8 Vishnu Nandan et al.
  • 1Centre for Earth Observation Science (CEOS), University of Manitoba, Canada
  • 2Department of Geography, University of Calgary, Canada
  • 3Centre for Polar Observation and Modeling, University College London, UK
  • 4Department of Geography, University of Victoria, Canada
  • 5DTU Space, Technical University of Denmark, Denmark
  • 6Centre for Integrated Remote Sensing and Forecasting for Arctic Operations (CIRFA), UiT The Arctic University of Norway, Tromsø, Norway
  • 7Thayer School of Engineering, Dartmouth College, USA
  • 8Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 9WSL Institute for Snow and Avalanche Research (SLF), Davos, Switzerland
  • 10CRYOS, School of Architecture, Civil and Environmental Engineering, EPFL, Lausanne, Switzerland
  • 11Institute of Environmental Physics, University of Bremen, Germany
  • 12ProSensing Inc, Amherst, MA, USA
  • 13Norce Norwegian Research Centre AS, Bergen, Norway
  • 14Physical Sciences Laboratory, NOAA, USA
  • 15Department of Geography and Environmental Management, University of Waterloo, Canada
  • 16H2O Geomatics Inc., Waterloo, Canada

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: open (until 23 Sep 2022)

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  • CC1: 'Comment on tc-2022-116', Andrew Shepherd, 01 Aug 2022 reply

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.