Mission Underway to Investigate Legacy Munitions in the Baltic Sea

The Baltic Sea is contaminated with remnants of munitions from past wars, but many questions remain about the exact locations of these munitions and their condition after decades under water.

Three major projects at national, Baltic Sea and European levels are currently working to consolidate existing knowledge and develop technologies to safely identify submerged munitions. GEOMAR Helmholtz Center for Ocean Research Kiel is contributing to these efforts with three Baltic Sea expeditions.

The first mission has now begun: the research vessel Alkor is being used to develop mapping and analysis techniques in German and Danish waters, with a particular focus on the sea areas at the exit of the Flensburg Fjord / Lille Belt, west of Bornholm and the Bay of Lübeck.

Expedition AL628 will collect data for three major munitions projects: CONMAR, which investigates munitions management in German waters; MUNI-RISK, which focuses on the entire Baltic Sea; and MMinE-SwEEPER, a nine-country European research effort. In addition to scientific and technological objectives — such as assessing munitions contamination and improving autonomous mapping and analysis methods — the expedition also promotes international cooperation.

The two autonomous underwater vehicles and the small blue remotely operated vehicle from GEOMAR are being employed for the expedition.

Developing appropriate guidelines is one of the tasks of the MUNI-RISK project (Mitigation of Risks Due to Submerged Munitions for a Sustainable Development of the Baltic Sea). This EU-funded project, led by the University of Aarhus, has been bringing together experts from a variety of research fields to develop concrete tools and guidelines that will enable the Baltic Sea countries to better assess the risks posed by munitions.

Next, Alkor will head to munitions dumping sites in the Bay of Lübeck, where researchers from the Polish institute IOPAN and the German Federal Police will join the expedition. The final destination will be off the coast of Boltenhagen, where a barge loaded with conventional munitions was sunk after the Second World War. The contents of the barge, which is lying on the seabed, will be cleared by an explosive ordnance disposal company from Rostock in June and July.

The next expedition is planned for October 2025 and will focus on investigating chemical munitions in Polish waters.

An estimated 40,000 tonnes of chemical munitions from World War II, along with over one million tonnes of unexploded ordnance (UXO), lie submerged in the Baltic Sea. Containing hazardous substances like mustard gas and arsenic compounds, often in corroding containers, these munitions pose serious risks to marine ecosystems, human health, and industries such as fishing and offshore wind energy.