Chinese Journal of Polar Research

Chinese Journal of Polar Research ›› 2026, Vol. 38 ›› Issue (3): 386-399.DOI: 10.13679/j.jdyj.20240092

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Comparison of Arctic sea ice freeboard products from multi-source satellite altimeters

LIANG Beibei1, 2, HE Lian1, 2, HUI Fengming1, 2, CHENG Xiao1, 2   

  1. 1School of Geospatial Engineering and Science, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China;
    2Key Laboratory of Comprehensive Observation of Polar Environment (Sun Yat-sen University), Ministry of Education, Zhuhai 519082, China
  • Received:2024-10-21 Revised:2025-02-10 Online:2026-09-30 Published:2026-10-22
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Abstract:

Satellite altimeter has been recognized as one of the important tools to derive long-term and large-scale sea ice thickness in the polar regions. This study aims to compare five Arctic sea ice freeboard products derived from five different satellite altimeters currently in orbit, including CryoSat-2 (CS2), SARAL/AltiKa (AltiKa), Sentinel-3A (S3A), Sentinel-3B (S3B) and ICESat-2 (IS2). The consistency between different sea ice freeboards during the winter season (October to April) was analyzed and their accuracies were evaluated using the Operation IceBridge (OIB) airborne observation data. The AltiKa radar sea ice freeboards were calibrated relative to the IS2 observations to remove the systematic bias. Validation with OIB airborne observations shows overall performance of CS2 and S3A with the mean bias and root mean square error (ERMSE) values being about 0.030 m and 0.077 m, respectively. The mean bias and ERMSE values for IS2 are –0.001 m and 0.070 m, respectively. AltiKa tends to systematically underestimate total sea ice freeboards compared to OIB measurements with the mean bias and ERMSE values being about –0.154 m and 0.190 m, respectively. For the radar sea ice freeboards derived from CS2, S3A and S3B, the difference between S3A and S3B is within ±0.002 m and the discrepancy between CS2 and S3A/B is within ±0.010 m, indicating a good consistency among these three sea ice freeboard observations. The AltiKa radar sea ice freeboards are significantly lower than IS2 laser sea ice freeboards with the mean bias ranging from 0.041 m to 0.161 m, and the mean bias increases from October to April as sea ice grows. After calibrating AltiKa on IS2, the corrected AltiKa shows improved accuracy with bias and ERMSE values being 0.031 m and 0.109 m, respectively. This study helps to understand the consistency between Arctic sea ice freeboards from different satellite altimeters and to obtain long-term, consistent sea ice freeboard and sea ice thickness data, which supports the study of fusion of multi-source sea ice freeboard products and estimation of snow depth on Arctic sea ice based freeboard differencing method.


Key words: Artic sea ice, satellite altimeter, sea ice freeboard, comparison analysis