Munition Piles in the German Baltic Sea: Inventory and Maritime Hazard Perspectives

Abstract. For the first time, this paper presents two datasets that detail the distribution of piles of dumped munitions in the German Baltic Sea (Lübeck Bay and north of Kiel Fjord). Multibeam echosounder data and photomosaics were collected between 2017 and 2024. Dataset A contains basic information on 484 known and potential munition piles and their geographic context, with a focus on maritime activities in their surroundings. Dataset B is a subset of the former, where visual investigation enabled the detailed assessment of 39 munition piles by experts, so that a greater level of detail on the properties of the munitions was collected. The paper contextualises the data in terms of the munitions' properties and their geospatial surroundings. It identifies a "typical" munition pile to be inhomogeneous, most likely layered, with partially buried objects and munition casings that are weakly corroded. Munition pile properties were found to differ between dump sites—particularly in terms of the number and size of objects on a pile. Based on the information in datasets A and B, it was possible to extrapolate the number of objects on all (potential) munition piles across Lübeck Bay. The assessment demonstrates that survey data do not match historic recordings in archival documents. Distance measurements reveal that munition piles are located close to protected areas and sediment deposit sites, while subsea cables are located furthest away. The paper identifies six clusters of munition piles, two of which are located in areas with very high traffic density (> 2,000 vessels annually). These data are presented to encourage scientific debate on holistic management strategies, clearance approaches, cost estimates, policy relevance, and prioritisation of remediation activities. The findings show that several munition piles require attention by the respective authorities.