Sea level rise in the Baltic Sea: Data from Estonian coastal tide gauges over 30 years

This study investigates the rate of sea level rise along the Estonian coastline of the Baltic Sea over the three decades (1993–2022) using tide gauge data and advanced analytical methods. Tide gauge data were analyzed using an open-source software based on the “TG Analysis” method developed by Kristian Breili. The results reveal significant spatial and temporal variability: the average relative sea level rise was 1.35 ± 1.91 mm/yr over the three decades, with a notable acceleration to 9.01 ± 8.67 mm/yr in the last decade (2013–2022). Absolute sea level rise, after correction for land uplift (NKG2016LU), averaged 4.16 ± 1.81 mm/yr. Regional differences were observed, with faster relative sea level rise in areas of slower land uplift (e.g., Pärnu, Virtsu) and vice versa. The data and trends were further analyzed by applying advanced analytical methods (differentiation, spectral and segmented regression analysis, and sea level model validation). By differentiating the sea level rise trends along the Estonian coast, and comparing tide gauge data with data from Stockholm and Hanko, the results show a minimal velocity difference (0.65 mm/yr), confirming the reliability of the trends. Spectral analysis and segmented regression analysis identified breakpoints mainly in the early 1990s, with the transition to automated tide gauges in 2010 having no significant impact. Validation of the ESA BalticSEAL model showed good performance in western Estonia, while larger discrepancies were observed in the northern regions, which are linked to local geophysical factor.