## 1 Introduction
### Prospective Use of LNG in the Baltic Sea  
In view of the above, a comprehensive analysis of the hydrological and meteorological conditions in the southern Baltic is required for optimal planning and implementation of LNG investment projects. With these factors taken into consideration, the safety of navigation can be enhanced, the operational effectiveness of LNG terminals improved, and possible hazards to the operation of the LNG infrastructure mitigated. Considering the increasing demand for low-emission energy sources, the development of LNG infrastructure in the southern Baltic Sea is regarded as a key component of the region's energy and maritime strategy [18]. In the context of global efforts to develope transport and reduce greenhouse gas emissions, LNG is widely presented as an alternative to conventional marine fuels, such as heavy fuel oil and coal. Its technical advantages--including high energy density, reduced emissions of sulfur oxides, nitrogen oxides, and particulates, as well as relative transport safety--position LNG as an important transitional fuel in maritime decarbonization [19; 20; 21; 22; 23; 24; 25; 26; 27; 28]. This perception is reinforced by current European Union policy frameworks. The Fit for 55 package aims to reduce net GHG emissions by at least 55% by 2030 and includes regulatory instruments like the Alternative Fuels Infrastructure Regulation, which mandates the provision of LNG bunkering facilities at core TEN-T ports by 2025. IMO introduces carbon intensity limits for marine fuels used in European waters, further incentivizing the shift toward cleaner fuels. On the international level, IMO sets a target of reducing GHG emissions from international shipping by 50% by 2050, encouraging the adoption of low-carbon and transitional fuels, including LNG. In addition, MARPOL Annex VI imposes a global sulfur cap of 0.5% in marine fuels, with stricter limits of 0.1% in Emission Control Areas, such as the Baltic and North Seas. LNG complies with these standards without requiring additional exhaust gas cleaning systems. The Baltic Sea, classified as both a Sulfur Emission Control Area and a Nitrogen Emission Control Area, offers a particularly favorable regulatory environment for LNG deployment. However, the assumption that LNG represents an inevitable or permanent solution is not sufficiently substantiated. LNG is best viewed as a transitional fuel that enables partial emission reductions while longer-term zero-emission technologies continue to mature. Alternative marine fuels, such as green ammonia, hydrogen, and methanol, are under active development and may offer greater long-term climate benefits. Moreover, concerns about unburned methane emissions (\"methane slip\") from LNG-powered engines call into question the net climate advantage of LNG over its full lifecycle. Therefore, while LNG can facilitate near-term compliance with environmental regulations, its long-term role remains uncertain and should not be overstated in strategic investment decisions. From an operational perspective, the southern Baltic presents a range of meteorological and hydrological challenges for LNG infrastructure and vessel traffic. As a semi-enclosed basin with limited tidal exchange, the region is subject to rapidly changing weather patterns, strong seasonal winds, icing conditions, and frequent storms. These factors may temporarily disrupt bunkering operations or compromise navigational safety. Climate change is expected to intensify such phenomena, increasing the need for resilient infrastructure and adaptive risk management [29]. In this context, investment in LNG must be accompanied by enhancements in port infrastructure, such as reinforced mooring facilities, heated bunkering systems, and anticiping technologies, as well as the implementation of real-time environmental monitoring, weather forecasting, and flexible operational protocols.