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Abstract:
Inconsistency in vertical reference surfaces between various sea-level data sources delivers a significant barrier to synergizing different sea-level approaches, which allows the determination of a realistic state of dynamic topography. As a result, transferring datasets with different approaches to a common and stable reference surface with a fixed reference epoch is feasible. Hence, a high-resolution geoid plays the role of a key component to link different sources. This study develops a method to reanalyze hydrodynamic model-based (HDM) sea levels via geoid-referenced tide gauges (TG). Thus, the steps of transferring datasets to a common vertical reference (including the same coordinate system, permanent tide system, and reference epoch) are demonstrated. Therefore, a comparison study allows us to highlight discrepancies between data sources and approach a realistic dynamic topography. The method is tested on the Baltic Sea using a dense network of TG stations, a high-resolution HDM, and Sentinel-3A satellite altimetry (SA) data for the period of 2017‒2021.Results show that the mean dynamic topography of corrected HDM is better by a factor of about 1.5. Validation with the Sentinel-3A satellite along-track data confirms the corrected HDM data to be more accurate than the original HDM. The synergy of different sources also identified problematic locations of HDM, SA, and geoid data, along with unreliable TG. For instance, the method identified a possible geoid problem in the eastern Baltic, which may be due to a lack of gravity data. The results are promising and the method can be applied to other sea areas.
