The impact of nonlinear tide-surge interaction on satellite radar altimeter-derived tides

• Published in: Marine geodesy 2023-05, Vol.46 (3), p.251-270
• Main Authors: Guarneri, H., Verlaan, M., Slobbe, D. C., Veenstra, J., Zijl, F., Pietrzak, J., Snellen, M., Keyzer, L., Afrasteh, Y., Klees, R.
• Format: Article
• Language: English
• Subjects: Altimeters; Altimetry; Atmospheric correction; Atmospheric models; Coastal waters; Continental shelves; Finite element method; Harmonic analysis; Modelling; Ocean models; Oceans; Radar altimeters; Radio altimeters; Satellite altimetry; Satellite radar; satellite radar altimetry; shallow waters; Tidal constituents; Tidal models; Tide gauges; tide-surge interactions; Tides; Time series; variance reduction; Water levels
• ISSN: 0149-0419; 1521-060X
• DOI: 10.1080/01490419.2023.2175084

Both empirical and assimilative global ocean tidal models are significantly more accurate in the deep ocean than in shelf and coastal waters. In this study, we answered whether this is due to the quality of the models used to reduce tide and surge or the general approach to treat tide and surge as two separate components of the water level obtained from stand-alone models, which ignores the nonlinear tide-surge interaction. In doing so, we used tide gauge observations as partially synthetic altimeter time series, tide-surge water-level time series obtained with the 2D Dutch Continental Shelf Model - Flexible Mesh (DCSM), and tide and surge water-level time series obtained using the DCSM, FES2014 (FES) and the Dynamic Atmospheric Correction (DAC) product. Expressed in the root-sum-square (RSS) of the eight main tidal constituents, we obtained a reduction % when removing the DCSM tide-surge water levels compared to when we removed the sum of the DCSM tide and DCSM surge water levels. The RSS obtained in the latter case was only 3.3% lower than with FES and DAC. We conclude that the lower tidal estimates accuracy in shelf-coastal waters derives from the missing nonlinear tide-surge interactions.