Preprints
https://doi.org/10.5194/egusphere-2024-2054
https://doi.org/10.5194/egusphere-2024-2054
22 Jul 2024
 | 22 Jul 2024

Dual-frequency radar observations of snowmelt processes on Antarctic perennial sea ice by CFOSCAT and ASCAT

Rui Xu, Chaofang Zhao, Stefanie Arndt, and Christian Haas

Abstract. Since 2017, Antarctic sea ice coverage has shown strong reductions, and therefore observations of its surface melting behavior are of utmost importance. Here we study the capability of the Ku-band Chinese-French Oceanography Satellite Scatterometer (CFOSCAT) launched in 2018 to detect surface melting and compare it with more established observations of the C-band Advanced Scatterometer (ASCAT) in orbit since 2007. Both CFOSCAT and ASCAT observations show increases of radar backscatter of more than 2 dB over perennial ice once the ice surface warms and destructive snow metamorphism commences, defined as pre-melt onset (PMO). Backscatter increases by more than 3 dB once prominent thaw-freeze cycles commence, defined as snowmelt onset (SMO). Scatterometer data are compared with drifting buoy and ERA5 reanalysis air temperature data to support the interpretation of melt-related snow processes. Between 2019 and 2022, the average CFOSCAT pre-melt and snowmelt onset dates for 12 perennial ice study regions are Nov 9±23 days and Dec 1±22 days and earlier than those of ASCAT on Nov 21±22 days and Dec 11±25 days, respectively. Sensitivity tests show that results slightly depend on chosen backscatter thresholds but little on sea ice concentration. The derived SMO are in good agreement with previous studies, but the SMO difference between dual-frequency radar observations is smaller than that reported by previous studies due to the sensor differences and different spatiotemporal resolutions. SMO differences between dual-frequency radar observations were also found to be potentially related to regional differences in snow metamorphism. With regard to the long-term changes in SMO, there is strong interannual and regional variabilities in SMO changes and no clear changes could be detected concurrently with the beginning of Antarctic sea ice decline after 2015. Dual-frequency CFOSCAT and ASCAT observations hold strong promise for better understanding of snowmelt processes on Antarctic sea ice and it is necessary to extend the observation of Antarctic snowmelt based on dual-frequency scatterometers.

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Rui Xu, Chaofang Zhao, Stefanie Arndt, and Christian Haas

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2054', Anonymous Referee #1, 23 Jul 2024
    • AC1: 'Reply on RC1', Rui Xu, 30 Aug 2024
  • RC2: 'Comment on egusphere-2024-2054', Anonymous Referee #2, 31 Jul 2024
    • AC2: 'Reply on RC2', Rui Xu, 31 Aug 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2054', Anonymous Referee #1, 23 Jul 2024
    • AC1: 'Reply on RC1', Rui Xu, 30 Aug 2024
  • RC2: 'Comment on egusphere-2024-2054', Anonymous Referee #2, 31 Jul 2024
    • AC2: 'Reply on RC2', Rui Xu, 31 Aug 2024
Rui Xu, Chaofang Zhao, Stefanie Arndt, and Christian Haas
Rui Xu, Chaofang Zhao, Stefanie Arndt, and Christian Haas

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Short summary
The onset of snowmelt on Antarctic sea ice is an important indicator of sea ice change. In this study, we used two radar scatterometers to detect the onset of snowmelt on the perennial Antarctic sea ice. It shows that since 2007, the snowmelt onset has demonstrated strong interannual and regional variabilities. We also found that the difference of snowmelt onsets between the two scatterometers is closely related to snow metamorphism.