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

• The Black Sea faces a long-term danger from naval mines in the Russia-Ukraine war.
• Ships have struck drifting mines in the last two years as Ukraine struggled to clear shipping routes.
• But even after the war, it's not clear how long it'll take to clear the waters.

Against all odds, Ukraine has gained the initiative in the Black Sea.

But a silent threat under the waves is poised to long outlast Russia's aggression: an unknown number of naval mines likely laid by both sides.

Even their locations — classified information to each of the warring parties — have become an open question as multiple incidents indicate that some have been drifting.

The issue is underscored by recent joint exercises between the US and NATO partners off the coast of Bulgaria, where it was announced that US and allied reconnaissance aircraft had spotted more than 100 mines in the Black Sea since the start of Russia's full-scale invasion. At least five ships have been affected, US 6th Fleet commander Vice Adm. Thomas Ishee said.

Keeping sea lanes clear of mines is critical to Ukraine's ability to export grain — in December last year, Ukraine said that a Panama-flagged bulk carrier had struck a mine, injuring two.

They've also washed up on Black Sea shores well beyond Ukraine's territorial waters — most recently on August 13, when Romanian authorities conducted a controlled explosion of a mine in a Danube conservation area.

Today, ships are passing through Ukraine's grain corridor with relative confidence, although they remain on alert.

"The threat of mines in the Black Sea still exists," Arlo Abrahamson, head of public affairs at NATO Maritime Command, told Business Insider.

They pose a threat to the Black Sea's coastal dwellers and seafarers and, in enough numbers, could threaten the region's economies and grain shipments.

It's unclear how many remain out there — and nobody knows how long it will take to clear up.

Combing the sea

Landmine clearance work is slow — and naval mine clearance is slower, said Steve Horell, a former naval intelligence officer and a senior defense fellow at the Center for European Policy Analysis.

"It's inaccurate to say 'demining' about naval mines," he said. The relevant term at sea — "mine countermeasures" — is a testament to how much harder it is to ensure there's not an explosive still lurking somewhere.

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.

But while it was short on ships, it had a large stock of Soviet-era naval mines, which it drew on for defenses.

Russia, too, had plenty of spare mines, and as incidents racked up all along the Black Sea's western coasts in 2022, it was soon accused of laying them.

It's a cheap and very easy thing to do.

"Any platform — ship, boat, submarine, aircraft — could be a mining platform," said Horell. "And with varying degrees of sophistication, you could basically have a general-purpose fishing boat or work boat and just push these things off the back."

It's unclear exactly how many have been laid; Estimates initially ranged in the hundreds, with Ukraine regularly accusing Russia of air-dropping more.

Mines where you really don't want them

In the simplest possible terms, the Black Sea's main currents run counter-clockwise and, according to Horell, take "about three to six months for a full rotation."

It means that "any naval mining, in pretty short order, becomes a risk and a threat in the entire Black Sea," he said.

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.

But — as part of broader objections to fossil fuel extraction — Greenpeace said in a June 2024 report that OMV Petrom and Romgaz' impact assessment "fails to consider the risk caused by naval mines."

The Greenpeace report's co-author Marc Dengler, a climate and energy expert at the campaign group, told BI last week that this is a serious omission. The main risk would be the danger to ships and workers during the construction phase, he said.

"But it can also hit the platform itself and especially the pipeline," he added. The consequences to the environment would be "really, really dramatic," he said.

Romgaz and OMV Petrom did not respond to Business Insider's request for comment.

Considering Greenpeace's concerns, Peters acknowledged that the extraction area is close to a mined war zone. But Romania's navy is well equipped at detecting and dealing with mine encounters, he said.

For Horrell, the security relief brought about by reducing Europe's dependence on Russian energy outweighs concerns about mines impacting the project.

"Certainly there's ecological risks to any offshore drilling, but to suggest that the risk of a floating mine vastly increasing that, is to me a stretch," he said.

Tomorrow's problem

Earlier this year, Turkey, Bulgaria, and Romania — the three countries other than Ukraine most affected by the drifting mine threat — banded together in a naval alliance to clear their waters.

Three ships will go mine hunting at least twice every six months, Defense News reported.

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."