![]() ![]() The Baltic Sea is a semi-enclosed shallow basin in northern Europe and is connected to the North Sea through the Danish Strait. The difference in observation systems of these two space-borne techniques makes them complementary tools to conduct analyses, draw conclusions, and validate their results ( Barnoud et al., 2021). The barystatic sea level is the mass component of the sea level, representing the change in the hydrostatic pressure above the ocean bottom ( Gregory et al., 2019 Dobslaw et al., 2020). Satellite altimetry and satellite gravimetry missions are two of these sources that measure the total and barystatic sea level changes, respectively. To this extent, space-borne observations are now providing us with reliable data sets for the last three decades. The need for a better understanding of regional drivers and patterns of sea level signifies as climate change shows severer impacts. A drop in the North Sea level can be seen from 2005 to 2011 which is followed by the Baltic Sea level with a ~3-year lag, implying the outflow from the Baltic Sea to the North Sea. The sea level variation in the North Sea is also examined to deduce the water exchange patterns on different time scales. Additionally, we show that the interannual variations of the barystatic sea level are governed by the North Atlantic Oscillation in the basin. It is shown that despite its insignificant contributions to seasonal and interannual changes, the steric sea level plays an important role in decadal variations. The total sea level and its contributors are further decomposed into seasonal, interannual, and decadal temporal components. Considering the dominance of barystatic sea level variations in the basin and the limitation of satellite gravimetry in resolving the mass change in water-land transition zones (known as the leakage problem), the mismatch is likely attributed to the inadequate accuracy of the barystatic datasets. We show that the sum of barystatic and steric components exhibits excellent cross correlation (0.9) with satellite altimetry sea level variations and also explains up to 84% of total signal variability from 2002 to 2019. To estimate the steric sea level, the density variations are weighted in deeper layers to prevent overestimation of their contribution. Satellite altimetry, satellite gravimetry, and in-situ subsurface salinity and temperature profiles are used to investigate the total, barystatic, and steric sea level variations in the Baltic Sea, respectively. 3Deutsches Geodätisches Forschungsinstitut der Technischen Universität München, Munich, Germany.2Department of Geosciences, Virginia Tech, Blacksburg, VA, United States.1School of Architecture and the Built Environment, KTH Royal Institute of Technology, Stockholm, Sweden.Armin Agha Karimi 1* Khosro Ghobadi-Far 2 Marcello Passaro 3 ![]()
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