Interpreting the Altimetric Radar Cross Section of Young Sea Ice
Abstract
Ku-band radar altimeters such as the one onboard CryoSat-2 measure the return-time of backscattered radar pulses to derive sea ice freeboard and thickness. This method relies on the two-way penetration of radar waves through the overlying snow. Early research with a surface-based radar over tank-grown sea ice indicated that most radar power is returned from the sea ice surface rather than the overlying snow, but this has not been replicated by in-situ radars in the field. We present a 24-day timeseries of surface-based radar measurements from young Antarctic sea ice (growing from 20 to 36 cm in thickness), showing a progressive reduction in its normalised radar cross-section (σ0) over time. This is associated with weakening of very strong, single-peaked waveforms associated with specular reflection from the ice surface; these initially swamp the signal from the snow surface but rapidly diminish with snow and ice ageing. Our observations help resolve the apparent contradiction between previous surface-based studies, and are consistent with an early-winter decline in σ0 observed by CryoSat-2. Our results also highlight the suppressing effect of frost flowers on σ0, and the similarity of σ0 evolution between the Ku- and Ka-bands. Our findings are relevant to the capability of the planned Ku/Ka-band CRISTAL altimetry mission, which aims to leverage differential radar penetration through snow on sea ice.
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BibTeX
@article{mallett2026interpreting,
title = {{Interpreting the Altimetric Radar Cross Section of Young Sea Ice}},
author = {Robbie Mallett and Vishnu Nandan and Julienne Stroeve and Rosemary Willatt and Thomas Newman and Gaelle Veyssiere and Carmen Nab and Connor Nelson and John Yackel and Amy Macfarlane and Jeremy Wilkinson},
journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
year = {2026},
month = oct,
doi = {10.1109/jstars.2026.3735896},
url = {https://hal.science/hal-05820768v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Interpreting the Altimetric Radar Cross Section of Young Sea Ice
AU - Robbie Mallett
AU - Vishnu Nandan
AU - Julienne Stroeve
AU - Rosemary Willatt
AU - Thomas Newman
AU - Gaelle Veyssiere
AU - Carmen Nab
AU - Connor Nelson
AU - John Yackel
AU - Amy Macfarlane
AU - Jeremy Wilkinson
PY - 2026
DA - 2026/10/20
JO - IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
DO - 10.1109/jstars.2026.3735896
UR - https://hal.science/hal-05820768v1
AB - Ku-band radar altimeters such as the one onboard CryoSat-2 measure the return-time of backscattered radar pulses to derive sea ice freeboard and thickness. This method relies on the two-way penetration of radar waves through the overlying snow. Early research with a surface-based radar over tank-grown sea ice indicated that most radar power is returned from the sea ice surface rather than the overlying snow, but this has not been replicated by in-situ radars in the field. We present a 24-day timeseries of surface-based radar measurements from young Antarctic sea ice (growing from 20 to 36 cm in thickness), showing a progressive reduction in its normalised radar cross-section (σ0) over time. This is associated with weakening of very strong, single-peaked waveforms associated with specular reflection from the ice surface; these initially swamp the signal from the snow surface but rapidly diminish with snow and ice ageing. Our observations help resolve the apparent contradiction between previous surface-based studies, and are consistent with an early-winter decline in σ0 observed by CryoSat-2. Our results also highlight the suppressing effect of frost flowers on σ0, and the similarity of σ0 evolution between the Ku- and Ka-bands. Our findings are relevant to the capability of the planned Ku/Ka-band CRISTAL altimetry mission, which aims to leverage differential radar penetration through snow on sea ice.
SN - 1939-1404
ER -