Marine geodetic references, such as the mean sea surface (MSS), are currently limited by the spatial resolution of conventional satellite altimeters. We analyze the new swath‐altimetry data from the Surface Water and Ocean Topography (SWOT) satellite, to determine the performance of SWOT for mapping the static ocean topography, and possible benefit of inclusion in future reference models. By determining how well SWOT observes the static features in the ocean surface during SWOTs fast‐sampling phase, we have determined the expected performance during the science phase of the mission. We observe a 50% reduction in variability of the static surface compared with Sentinel‐3, whilst resolving up to 36% shorter wavelengths (down to 8 km) compared to the current state‐of‐the‐art Hybrid23 MSS reference model. Comparisons with Sentinel‐3 show that SWOT will benefit the current altimetry record.

Using the Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) global high-resolution elevation measurements, it is possible to distinguish individual surface ocean waves. With the vast majority of ocean surveying missions using radar satellites, ICESat-2 observations are an important addition to ocean surveys. ICESat-2 can also provide additional observations not possible with radar. In this paper, we consolidate the ICESat-2 ocean observations by comparing the significant wave height (SWH) with coincident CryoSat-2 radar observations during the CRYO2ICE campaign from August 2020 to August 2021. We use 136 orbit segments, constrained to the Pacific and Atlantic oceans as well as the Bering Sea, to compare observations to show the level of agreement between these systems. Three models based on ICESat-2 are used in the comparison: the standard ocean data output (ATL12), a method of modeling the individual surface waves using the geolocated photons and, functioning as a baseline, an approach using the standard deviation of the ocean surface. We find the following correlations between the SWHs from the models and the SWHs from CryoSat-2: 0.97 for ATL12, 0.95 for the observed waves model, and 0.97 for the standard deviation model. In the same comparison, we find mean differences relative to the observed SWHs for each model, as well as errors, which increase as the SWH increases. The SWH observed from ICESat-2 is found to agree with observations from CryoSat-2, with limitations due to changes in the sea state between the satellite observations. Observing the individual surface waves from ICESat-2 can therefore provide additional observed properties of the sea state that can be used alongside other global observations.

Tsunamis from large subduction earthquakes pose severe coastal hazards, yet their genesis near the trench remains poorly constrained by land-based seismic geodetic data and distant deep-water sensors. Following the 29 July 2025 magnitude 8.8 Kamchatka earthquake, the NASA/CNES Surface Water and Ocean Topography (SWOT) satellite captured a distinct train of short-wavelength tsunami waves, which we link to near-trench tsunamigenesis. Sensitivity analyses of earthquake slip indicated tsunamigenesis within 10 kilometers of the trench, an inference not attainable from land seismology and geodesy or sparse deep-water seafloor pressure records alone. These results provide the first high-resolution, two-dimensional spaceborne observation directly linking the measured dispersive tsunami wavefield to near-trench tsunamigenesis, extending earlier model- and gauge-based inferences. They establish SWOT as a constraint on source processes, with implications for tsunami hazard science and subduction-zone geodynamics.

Using global high-resolution elevation measurements from the Ice, Cloud, and land Elevation Satellite 2 (ICESat-2), it is possible to distinguish individual surface ocean waves. As the majority of ocean surveying missions are radar satellites, ICESat-2 observations are an important addition to ocean surveys and can provide additional observations not possible with radar. By utilizing the coincident orbits between CryoSat-2 and ICESat-2 during the CRYO2ICE campaign, the observations from ICESat-2 are compared along long stretches of the ground tracks, rather than at the usual crossover points. Therefore, from August 2020 to August 2021, 136 orbit segments from ICESat-2 in the Pacific and Atlantic oceans are used in the comparison. To allow for comparison of ICESat-2 during the coincident orbits, CryoSat-2 is validated against in-situ stations as well as satellite altimetry measurements. Using the validated CryoSat-2 observations, the significant wave height (SWH) is determined from the individual photon heights observed by ICESat-2, by three different methods. First, by using the standard ocean data output (ATL12), the SWH determined from this can be further validated. Then, the two methods derived in this study contain a model of deriving the SWH directly from the observed surface waves, as well as a model using the same method as ATL12, to act as a baseline for the wave-based model. The validation of this wave-based model for extended stretches with CryoSat-2 would allow for the further use of this model for studies. The carried out comparisons result in correlations between ICESat-2 and CryoSat-2 of 0.97 for ATL12 and 0.95 for the wave-based model, with a small mean deviation between the altimeters. The observations from ICESat-2 experience a larger variance than other altimeter crossover-comparison studies, however being constrained by a larger time-lag (<3h) between the coincident orbits for ICESat-2 and CryoSat-2 this is expected. From the study, ICESat-2 is found to agree with observations from CryoSat-2, and utilizing the possibility of distinguishing the surface waves, would therefore provide beneficial for ocean observations.

We introduce a new Mean Sea Surface model (MSS) that incorporates the wide-swath altimetry obtained from the Surface Water and Ocean Topography (SWOT) satellite, along with long timeseries of conventional altimetry. The DTU25MSS constrains long wavelengths (>20 km) from a suite of conventional altimeters while utilizing almost 2 years of SWOT observations to reduce the short wavelength noise and incorporate previously unmapped geodetic features into the MSS. Parametric long wavelength corrections of the SWOT data in order to compensate for the short time-scale is presented, and the resulting MSS model is compared with contemporary MSS models as well as data from the SWOT Cal/Val orbit. The MSS is available on https://doi.org/10.11583/DTU.29412275 (Andersen and Nilsson, 2025), and includes an experimental MSS which has the reference period moved to 2023 as opposed to 2003, to compensate for sea level rise. To extend the MSS into the coastal zone, the high-resolution 250 m SWOT data is used close to the coast (<40 km), and resolves complex features previously not included. Using an updated MSS with better resolved short wavelength signals is seen to be a large benefit for interpreting the detailed SWOT observations with reduced leakage of geodetic features into the oceanographic signals, as well as 30 % increase in spatial resolution. Due to incorporating complex novel features in the coastal zone that have been resolved by SWOT the full effect on other more coarse observations is a potential for further studies. The SWOT data and utilization of it is only expected to be improved with time and further development of methods for utilizing this new dataset will move it closer to its full potentials.

We introduce a new Mean Sea Surface model (MSS) that incorporates the wide-swath altimetry obtained from the Surface Water and Ocean Topography (SWOT) satellite, along with long timeseries of conventional altimetry. The DTU25MSS constrains long wavelengths (> 20 km) from a suite of conventional altimeters while utilizing almost 2 years of SWOT observations to reduce the short wavelength noise and incorporate previously unmapped geodetic features into the MSS. Parametric long wavelength corrections of the SWOT data in order to compensate for the short time-scale is presented, and the resulting MSS model is compared with contemporary MSS models as well as data from the SWOT Cal/Val orbit. The MSS is available on http://doi.org/10.11583/DTU.29412275, and includes an experimental MSS which has the reference period moved to 2023 as opposed to 2003, to compensate for sea level rise. To extend the MSS into the coastal zone, the high-resolution 250 m SWOT data is used close to the coast (< 40 km), and resolves complex features previously not included. Using an updated MSS with better resolved short wavelength signals is seen to be a large benefit for interpreting the detailed SWOT observations with reduced leakage of geodetic features into the oceanographic signals, as well as ~30 % increase in spatial resolution. Due to incorporating complex novel features in the coastal zone that have been resolved by SWOT the full effect on other more coarse observations is a potential for further studies. The SWOT data and utilization of it is only expected to be improved with time and further development of methods for utilizing this new dataset will move it closer to its full potentials.