ICESat-2 surface elevation assessment with kinematic GPS and static GNSS near the ice divide in Greenland

Abstract. Since 2007, researchers have conducted monthly or bi-monthly kinematic GPS surveys along a 15-km transect near Summit Station, Greenland, providing ice surface elevation data with high relative accuracy (±0.8 cm) and high precision (±0.8 cm). We use these surveys to assess the long-term stability of ICESat-2 surface height measurements, revealing a sub-1.0 cm bias and sub-6.0 cm precision relative to ICESat-2 data, with no significant temporal trend in performance. While reliable, these surveys are resource-intensive. We introduce an alternative, novel validation method using autonomous GNSS stations with interferometric reflectometry (GNSS-IR) to measure surface elevation concurrent with ICESat-2 overflights. This method agrees well with kinematic GPS (-0.2 ± 5.0 cm) and is sensitive to active accumulation and surface roughness, offering additional environmental context. The ICESat-2 measurements are biased by -0.9 ± 3.8 cm compared to these autonomous stations. Together, these results demonstrate the importance of sustained, high-accuracy GNSS for building a long-term elevation benchmark record in Greenland, while also establishing GNSS-IR as a scalable alternative in support of current and future altimetry missions.