The Black Sea has a deadly naval mine problem that will long outlast the Ukraine war

On land, demining efforts focus on a single level, not particularly deep in the soil. But underwater, the search goes deep as well as wide.

Also, landmines tend to stay put. Once exploded, “at some point you can have some degree of certainty you’ve combed over this piece of earth,” as Horell put it. But at sea, a new mine could drift into the same spot the next day, he said.

Modern naval mines are generally triggered in two ways — a magnetic trigger, or a pressure-sensitive one, he said. Either way, you can’t move fast to remove them. Older mines can be triggered by contact with a ship’s hull.

“What you’ve got is, generally speaking, smaller ships moving slowly so that they don’t trigger the mines that they’re trying to find and disable, and just searching very painstakingly in repetitive patterns,” he said.

Mine-hunting is methodical, technical, and dangerous. Ships can also look for naval mines using sonar or magnetic detection, and helicopters and remote vehicles can also seek them out.

“But it’s always going to be that slow kind of an effort,” Horell said.

A desperate move

When Russia began its full-scale invasion in February 2022, Ukraine’s navy was badly outmatched.

Russia’s Black Sea Fleet flagship, the Moskva, prowled the waters, famously capturing Snake Island.

The Moskva — and Russian control of the island — are now distant memories. But at the time, Ukraine’s only available move was defensive. It scuttled its own flagship to prevent it falling into Russian hands.

A mine on the loose near Ukraine’s major port of Odesa — in the northwestern Black Sea — could within weeks pass through the territorial waters of Romania, Bulgaria, and Turkey.

Which is exactly what happened.

Several had been found drifting far from where a mine should be — one was so close to the Bosphorus, the Turkish channel that connects the Mediterranean to the Black Sea, that the strait had to be closed.

In May 2022, the International Maritime Organization sent out a warning about “a serious and immediate threat to the safety” of ships operating in the Black Sea due to free-floating mines.

How they started drifting is unclear.

Later, in 2023, the destruction of the Kakhovka Dam and a fierce winter storm both gave rise to worries that fixed mines could have become dislodged by flooding.

“It’s also quite plausible that Russia was adding more mines to the water in that situation,” said Horell.

It’s also not known for sure which types were in use, but several were reported to be contact mines anchored just below the water’s surface. One such contact mine, found off the coast of Bulgaria in July 2022, was a YaM mine — a Soviet-era anchor-type river mine that floats a few feet below the surface.

“So was it actually floating mines that came loose due to weather conditions, or were they placed intentionally to create a threat perception?” asked Johannes Peters, head of the Center for Maritime Strategy and Security at Kiel University in Germany. “We’re still not quite sure.”

“Most of the mines were quite old,” he added. “It doesn’t make them less dangerous, but we don’t know the maintenance situation.”

Anchored mines are required in international law to have a failsafe that neutralizes the explosive if they come loose, he said — but, he added, there’s no way of knowing if that mechanism still works.

The matter raised major fears for ships transiting Ukraine’s grain corridor, which Russia openly threatened after withdrawing from the Black Sea Grain Initiative in the summer of 2023.

Soon after, Ukraine’s armed forces accused Russia of dropping several mines onto the corridor, and in December 2023 a Panamanian-flagged cargo ship hit a mine, injuring two.

This was the last major incident between a commercial ship and a stray mine, and, Peters said, the volume of naval mines in these waters is likely much smaller than initially feared.

Today, the situation has stabilized; even as mines continue to wash up on beaches, exports have begun approaching pre-war levels.

Sounding the alarm

Nonetheless, campaigners at Greenpeace have concerns in connection to a major gas extraction project in the Black Sea.

Neptun Deep is a joint project of Romanian energy companies OMV Petrom and Romgaz to build an offshore gas field in Romanian territorial waters. Analysts say that the deepwater project, due to start pumping gas in 2027, is set to turn the country into a net exporter of gas, further freeing the continent from dependence on Russian energy.

The move is to be applauded, Horell said — but the “limited capacity of those three navies to do that is going to mean it would be a long time before you can have that sort of assurance.”

Clearing the rest of the Black Sea, including Ukraine’s own waters, may have to wait until long after the war.

A pair of minesweepers sold to Ukraine by the UK remain at anchor in Portsmouth. They’re blocked from entering the Black Sea by Turkey’s reading of the Montreux Convention, which bars warships passing through the Bosphorous in wartime.

In the absence of ships like that, Horell suggested other means, such as uncrewed mine-seeking vessels, that can pass through smaller waterways to the Black Sea.

Even after hostilities end, Ukraine has learned that any peace with Russia comes with few guarantees — and Ukraine may say: “‘Okay, we are not in a war anymore, but we are far away from peace as well,'” said Peters.

In that instance, Kyiv may decide to keep its coastal defenses in place.

For Peters, no one can say exactly how long it would take to clear the waters.

“It has a political dimension, it has a technical dimension, it has a capability dimension,” he said.

He added: “It’s hard to declare that ‘it is cleared.’ You just can define the degree of uncertainty you want to live with.”