In the Second World War, narrow sea areas such as fjords and straits suffered the most from mine warfare. Many Norwegian fjords were mined in the war and these old mines still cause danger for shipping and other human activities at sea. In addition to disposing naval mines from the Norwegian maritime area, the Norwegian Navy has made a strong contribution to the work of the NATO Mine Countermeasures Group, including in the Baltic Sea.
Countermining operations are necessary for ensuring the safety of shipping or clearing the area for construction activities, for example, the laying of submarine cables and pipelines, establishment of windfarms and bridges.
However, these operations cause significant noise pollution in the marine environment when the mines are detonated. This proves deadly for marine mammals even if they are many kilometers away from the explosion.