Impact of geophysical corrections on snow cover depth retrieval from CRYO2ICE campaign

Snow depth on sea ice is an important geophysical variable and a critical parameter for sea ice thickness retrieval from satellite altimetry. In recent years, the implementation of the CRYO2ICE coordinated observation campaign has provided a new opportunity for retrieving sea ice surface snow depth using combined radar and laser altimetry data. However, ocean dynamics and solid earth effects degrade altimetry accuracy, while varying geophysical correction models across altimetry products introduce biases in snow depth retrieval. This study systematically analyzed spatiotemporal differences in six major geophysical correction terms between CryoSat-2 and ICESat-2 altimetry products, based on CRYO2ICE coincident Arctic observations. Further, the impact of these differences on snow depth retrieval was quantified. Results show that ocean tide corrections exhibit the largest differences between the two altimetry products, characterized as random errors with significant spatial variability in shallow coastal areas. The inverse barometer corrections show significant systematic biases, particularly during autumn. While the solid earth tide corrections display relatively small overall biases but exhibit amplification effects in shallow coastal areas. In contrast, the long-period equilibrium tide, ocean loading tide, and geocentric polar tide corrections present minimal differences. Following the application of consistent geophysical correction models, the consistency of sea surface height anomaly at leads was enhanced, with mean absolute bias decreasing from 0.8 cm to 0.6 cm and standard deviation reducing from 8.0 cm to 7.6 cm. The impact assessment of different geophysical correction terms on snow depth retrieval results shows that: inverse barometer correction differences have the most widespread influence, with relative impacts exceeding 5% observed in 62.9% and 57.3% of the observation data in first-year ice and multiyear ice regions respectively; the ocean tide correction ranks second, with relative impacts exceeding 5% observed in 55.0% and 50.5% of the observation data in first-year ice and multiyear ice regions respectively, and relative impacts can reach 60% in Arctic marginal seas; other correction terms have relative impacts less than 5%. The magnitude of snow depth corrections increases significantly following the application of consistent correction models, demonstrating that geophysical correction model differences produce cumulative effects. The results offer scientific guidance for optimizing satellite altimetry data processing workflows and improving the precision of Arctic sea ice thickness remote sensing retrievals.