# Long-Term and Decadal Sea-Level Trends of the Baltic Sea Using Along-Track Satellite Altimetry
## 7 Conclusions  
This examination of coastal sea-level trends, calculated using tide gauges (TGs) and multi-mission along-track satellite altimetry (SA) for the period 1995-2022, showed that the average absolute sea-level trend for TG and along-track SA varies between 3.32 and 3.86 mm/yr. This agrees with previous regional Baltic Sea studies, with average values of 3 mm/yr, and that of the global mean sea level (GMSL) rate from TG and SA observations, which showed rates of 3.2 mm/yr over the period 1993-2015 to 3.6 mm/yr over the period 2006-2015. A spatial distribution of larger sea-level trends was observed in the northern and eastern areas of the Baltic Sea, and this may be due to increased days of intense westerly winds, lower air pressure, and increased sea temperature. Decadal sea-level trends showed quite a variation in rates, and a possible increase may have occurred in the decade 2000-2009. This study demonstrates that along-track instantaneous SA data can be reasonably utilized for sea-level trend estimates, and that they give a very good alternative for areas where TGs may not be present and for areas that may be influenced by gaps in TG data.  
M.M.: conceptualization, methodology, validation, formal analysis, writing, visualization. A.E.: conceptualization, writing--review and editing, supervision, funding. N.D.-E.:conceptualization, writing--review and editing, supervision. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research is supported by the Estonian Research Council (grants PRG1129 and PRG1785: \"Development of continuous dynamic vertical reference for maritime and offshore engineering by applying machine learning strategies/DYNAREF/\").  
**Data Availability Statement:** The employed NKG2015 geoid model was provided by [76], and the NKG2016 LU VLM model was provided by [75]. The Baltic + SEAL dataset is available on request from [[http://balticseal.eu/](http://balticseal.eu/)]([http://balticseal.eu/](http://balticseal.eu/)), and standard SA data are available from [[https://eoportal.eumtest.int/](https://eoportal.eumtest.int/)]([https://eoportal.eumtest.int/](https://eoportal.eumtest.int/)). TG observations are downloadable based on the data provider, which is mentioned in Table A1. Post-processed data are available based on request.  
**Acknowledgments:** The two anonymous reviewers are thanked for their comments that improved the quality of the manuscript. The authors are also thankful to the Baltic + SEAL project team (of the Technical University of Munich) for granting access to the dataset and the below-mentioned institutes for providing tide gauge records and support (cf. Table A1): Poland: Institute of Meteorology and Water Management (IMGW-PIB); Germany: Federal Maritime and Hydrographic Agency (BSH); Estonia: Estonian Environment Agency (KAUR); Latvia: Centre of Environmental Geology and Meteorology of Latvia (LVGMC); Finland: Finnish Meteorological Institute (FMI); and the Swedish Meteorological and Hydrological Institute (SMHI).  
**Conflicts of Interest:** The authors declare no conflicts of interest. The founders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
Figure 16: Annual DT [cm] variation in TG observations (hourly data) of ASL (GIA-corrected) for six selected TG stations during 1995–2022. The bottom and top of each bar are the 25 th and 75 th percentiles of the DT and the line in the middle of each box is the median value at each year.