Sea lanes are key to the movement of goods for everyday life. Around 90 percent of world trade is carried by ship. The same is often true for military forces on the move, while aircraft can fly in some amount of fuel, dry goods, food and ammunition; the majority of the supply chain often requires movement by sea.
To stop that movement, in wartime, naval mines may be laid to hinder access to a port or close off a channel or strait. Modern navies must be prepared to clear paths through these minefields and ensure open sea lanes to transport goods and people.
Mine countermeasures vessels are usually small ships, but specifically designed with the task of keeping the sea lanes open in mind. They are often built from the keel up to allow them to safely navigate near minefields and have the equipment and personnel to locate and neutralize the mines aboard.
Mine countermeasures ships are often designed to minimize the sound they produce (their acoustic signature) and the amount of magnetic material (ferrous) in their design. Mine countermeasures ships can be built of wood or glass-reinforced plastic. If steel hulls are used, the ship is demagnetized, or degaussed, before heading out on missions, all in an attempt to make the ships less noticeable to naval mines.
Modern mines come in multiple types with many different triggering mechanisms. Triggers can be set off by contact with the mine, detection of magnetic material, sound traveling through the water or pressure changes in the water to name only a few. Some may be tethered to or placed on the sea floor, while others float freely or are tethered to other mines in various configurations.
In order to counter this variety of mines, mine countermeasure ships also have a variety of techniques and equipment to find, identify and neutralize naval mines. Some ships are specialized to sweep for mines, dragging a wire or other equipment through the water to cut mine tethers and bring them to the surface to destroy, while others are specialized to hunt mines directly by using sophisticated sonar and remote controlled vehicles to find the mines. Still others can do both mine sweeping and mine hunting.
Keeping personnel out of the mine field is preferred as far as possible. Some systems like MCM Denmark use drones to locate the mines then remote vehicles to detonate the mine. Some mines require a more personal approach and require sending divers in to neutralize it once identified.
The men and women of the mine countermeasures force are trained and capable and practice using these skills on a regular basis. Standing NATO Mine Countermeasures Groups regularly practice their skills on live mines by conducting “historical ordinance disposal,” neutralizing mines from previous conflicts in the waters in and around NATO nations.
During exercise Noble Mariner, the intent is to work with practice mines, to train and work as a team, but if the group was to identify live historical ordinance, they would be ready.