# Long-Term and Decadal Sea-Level Trends of the Baltic Sea Using Along-Track Satellite Altimetry
## 6 Discussion  
In this study, an analysis was conducted on sea-level trends covering a long-term period (28 years, from 1995 to 2022) as well as decadal scales (2000-2009 and 2010-2020) with the focus mainly on the Baltic Proper within the Baltic Sea region. The dataset utilized \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**ID**} & \multirow{2}{*}{**TG (\(\bullet\))**} & \multirow{2}{*}{**SA (\(\bullet\))**} & \multicolumn{2}{c}{**Global SLA**} & \multirow{2}{*}{**Nemo (\(\bullet\))**} & \multirow{2}{*}{**SEAL (\(\bullet\))**} & \multirow{2}{*}{**TG (\(\blacktriangle\))**} & \multirow{2}{*}{**SA (\(\blacktriangle\))**} \\  & **1995–2019** & **1995–2019** & & & & & \\ \hline
1 & 1.07 \(\pm\) 0.31 & 3.25 \(\pm\) 0.11 & 4.33 \(\pm\) 0.0 & **2.05 \(\pm\) 0.0** & 3.82 \(\pm\) 0.03 & 3.6 \(\pm\) 0.02 & 2.8 \(\pm\) 0.01 \\
2 & 2.79 \(\pm\) 0.14 & **3.94 \(\pm\) 0.09** & 3.98 \(\pm\) 0.0 & NaN & 4.05 \(\pm\) 0.03 & 4.6 \(\pm\) 0.01 & 4.8 \(\pm\) 0.01 \\
3 & \(-\)0.3 \(\pm\) 0.17 & 4.01 \(\pm\) 0.10 & **3.85 \(\pm\) 0.0** & NaN & 4.38 \(\pm\) 0.03 & 2.1 \(\pm\) 0.01 & 5.4 \(\pm\) 0.01 \\
4 & 2.06 \(\pm\) 0.18 & 3.57 \(\pm\) 0.11 & 3.23 \(\pm\) 0.0 & **1.40 \(\pm\) 0.0** & 3.33 \(\pm\) 0.02 & 2.4 \(\pm\) 0.01 & 4.1 \(\pm\) 0.01 \\
5 & 1.11 \(\pm\) 0.18 & 2.92 \(\pm\) 0.13 & 3.28 \(\pm\) 0.0 & **1.33 \(\pm\) 0.0** & NaN & 2.1 \(\pm\) 0.01 & 3.1 \(\pm\) 0.01 \\
6 & 1.67 \(\pm\) 0.18 & **2.77 \(\pm\) 0.13** & 2.95 \(\pm\) 0.0 & NaN & NaN & 2.7 \(\pm\) 0.01 & 3.4 \(\pm\) 0.01 \\
7 & 2.50 \(\pm\) 0.12 & **2.37 \(\pm\) 0.09** & 3.40 \(\pm\) 0.0 & 1.40 \(\pm\) 0.2 & 2.84 \(\pm\) 0.02 & 3.2 \(\pm\) 0.01 & 2.7 \(\pm\) 0.01 \\
8 & 4.68 \(\pm\) 0.05 & 1.90 \(\pm\) 0.11 & **2.95 \(\pm\) 0.0** & NaN & 2.69 \(\pm\) 0.02 & 5.1 \(\pm\) 0.01 & 2.5 \(\pm\) 0.01 \\
9 & 1.88 \(\pm\) 0.06 & 3.43 \(\pm\) 0.09 & 3.38 \(\pm\) 0.0 & NaN & **3.34 \(\pm\) 0.02** & 3.5 \(\pm\) 0.01 & 4.1 \(\pm\) 0.01 \\
10 & 1.55 \(\pm\) 0.01 & 3.75 \(\pm\) 0.10 & **3.33 \(\pm\) 0.0** & NaN & 3.55 \(\pm\) 0.02 & 4.8 \(\pm\) 0.01 & 4.1 \(\pm\) 0.01 \\
11 & 2.80 \(\pm\) 0.03 & 4.82 \(\pm\) 0.16 & 3.13 \(\pm\) 0.0 & 1.85 \(\pm\) 0.0 & **3.09 \(\pm\) 0.03** & 4.9 \(\pm\) 0.01 & 5.3 \(\pm\) 0.01 \\
12 & 3.78 \(\pm\) 0.13 & **4.00 \(\pm\) 0.13** & 3.19 \(\pm\) 0.0 & 1.99 \(\pm\) 0.0 & 4.11 \(\pm\) 0.02 & 5.4 \(\pm\) 0.01 & 3.5 \(\pm\) 0.01 \\
13 & 3.74 \(\pm\) 0.13 & **4.05 \(\pm\) 0.10** & 4.82 \(\pm\) 0.0 & 2.30 \(\pm\) 0.0 & 5.09 \(\pm\) 0.03 & 5.4 \(\pm\) 0.01 & 4.5 \(\pm\) 0.01 \\ RMSE between TG (blue circle and triangle) and SA (red circle and triangle) pairs & 1.78 & 0.64 \\ \hline \end{tabular}
\end{table} 
Table 8: Sea-level trend estimates [mm/yr] during 1995–2019 using hourly TG observations, instantaneous SA-derived DT, and three gridded data products (incl. global gridded SLA, Baltic Sea Nemo gridded data, and Baltic + SEAL gridded data). The best performances compared to TG observations are in bold font. The ASL trend of TG and SA during 1995–2022 (from Figure 7 and Table 6) is also mentioned. The shape in parenthesis corresponds to the shapes in Figure 12.  
included information from 13 TG stations along with multi-mission along-track SA. Below is a summary of the key findings. To begin, on average, the long-term ASL trend calculated for the entire Baltic across the period 1995-2022 revealed consistent results: on average, 3.83 (cf. Table 5) mm/yr for TG hourly data, 3.87 mm/yr for instantaneous SA data, and 3.32 mm/yr for TG at the time of the SA pass (as indicated in Table 5). Notably, all three calculation methods demonstrated relatively similar outcomes. These findings align with prior studies over the same study area: [45] reported trend estimates of 3.4 mm/yr, [29] indicated 3 mm/yr, and [46] achieved comparable results for different time periods using SA, TG, and hydrodynamic models.