Early this week, three separate leaks were discovered in two giant natural gas pipelines from Russia. The pipelines were filled with the fuel, and the ruptures produced gas bubbles half a mile wide that rose to the surface of the Baltic Sea, near the Danish island of Bornholm.
Explosions had been detected nearby just before the leaks occurred, and European governments have not yet identified the cause of the leaks in the pipelines, known as Nord Stream 1 and Nord Stream 2. Political leaders in Europe and the United States have suggested that the incident was an act of sabotage.
Speculation has pointed to Russia, whose state-controlled energy company, Gazprom, is the main owner of the pipelines. A spokesman for President Vladimir V. Putin of Russia, Dmitri S. Peskov, dismissed allegations of Russian involvement as “stupid” and pointed a finger at the United States.
The situation bears the hallmarks of a spy thriller. But analysts say that damaging the pipelines could be a significant escalation in the proxy energy war that has been waged since fighting began in Ukraine — a battle that could have serious consequences for millions of homes and businesses throughout Europe. Indeed, whoever damaged the pipelines may have meant to show Europeans that “nowhere is safe,” said Helima Croft, the head of commodity strategy at RBC Capital Markets.
The damaged pipelines are critical links between Russia and Western Europe.
The two major lines were built to bring gas under the Baltic Sea from Russia to Germany.
Nord Stream 1, which began operating in 2011, was until recently the main conduit for bringing gas to Germany — enough to supply more than half of the country’s annual consumption and still pass some along to its neighbors. The pipeline is roughly 760 miles long, most of it underwater.
Construction was completed last year on the second line, Nord Stream 2, which was intended to double those flows, providing a big, modern line into northwest Europe. But it never became fully operational: The German government shelved the project in February, just as Russia began to invade Ukraine.
Even though European countries have cut back their consumption of natural gas in response to high prices and entreaties from their governments, the fuel remains of vital importance for heating homes and keeping businesses running.
Neither pipeline was actively transporting gas at the time of the incidents. Gazprom has recently throttled back Nord Stream 1, citing technical issues. Critics have dismissed the action as political maneuvering by Russia as the fighting in Ukraine drags on.
The leaks may help Russia by pushing energy prices higher.
In some respects, disrupting the pipelines serves little immediate purpose for anyone.
And, on the surface, it is unclear why Moscow would seek to damage installations that cost Gazprom billions of dollars to build and maintain. The leaks are expected to delay any possibility of receiving revenue from fuel going through the pipes.
On the other hand, the natural gas market is spooked, which helps Russia by raising the price of its gas. On Monday, prices for European gas futures had fallen by nearly half from their high in August. After news of the leaks, they rose nearly 20 percent to about 205 euros (or $191) per megawatt-hour, roughly five times the level of a year ago.
After months of increases and volatility, energy markets had recently begun to settle down as optimism grew that Europe could avoid shortages this winter by finding alternative supplies and filling gas storage facilities.
The ruptures could also be a reminder from Moscow that if European countries keep up their support for Ukraine, they risk sabotage to vital energy infrastructure. Experts have warned for years of the danger posed by potential attacks. According to analysts, any disruption could spell trouble because European countries that have been dependent on Russian gas, like Germany and Austria, have little margin for error.
Over the last year, Gazprom and Russia have taken steps like altering the flows on the Nord Stream 1 pipeline, which analysts say were intended to raise political tensions and energy prices.
This incident has sent a chill through the markets because it highlights that a “risk of disruption” to pipelines not controlled by Russia exists, said Massimo Di Odoardo, the vice president for gas research at Wood Mackenzie, an energy consulting firm.
The environmental impact appears alarming.
The damaged pipelines are spewing natural gas, which largely consists of methane, a central contributor to global warming.
As of Wednesday, more than half of the fuel that was in the pipelines had leaked out, according to Kristoffer Böttzauw, the head of the Danish Energy Agency. By Sunday, it could all be gone.
The toll from the leaks could amount to the equivalent of 32 percent of Denmark’s annual emissions, Mr. Böttzauw said, adding, “There is a significant climate impact because methane is many times more damaging to the climate than CO2.”
Antoine Rostand, a co-founder of Kayrros, which uses satellites to track methane leaks from oil wells and gas processing facilities, estimated that the damaged pipelines had released an amount comparable to one day of methane emissions by the oil and gas industry globally.
Scientists hope that the gas, which is rushing to the surface and dispersing into the atmosphere, will not have a major impact on animal and plant life in the waters around the leak.
The damage points to explosive devices.
The pipelines are built of steel coated with concrete so that they can withstand underwater pressures. In other words, it takes a lot of force to damage them.
“A gas leak of this nature is extremely rare,” Mr. Böttzauw said. “It is unlikely that three gas leaks would occur in one accident within 24 hours.”
Swedish seismologists on Monday detected two separate underwater explosions near where the leaks were later identified. Both lines of Nord Stream 1 were damaged, whereas only one of Nord Stream 2’s lines was ruptured, which means that, at least theoretically, gas could flow through the second line.
Hans Liwang, a professor at the Royal Institute of Technology in Sweden, said examining the size of the crater on the seabed and the damage to the pipes could provide answers about the size of the explosive charge and the locations of the blasts.
“We will probably be able to figure out where this explosive device was placed by looking at the traces on the bottom,” he told Sweden’s Svenska Dagbladet newspaper.
But he added that leaking gas might have blown away important evidence, especially if, as some have speculated, the sabotage was carried out using underwater drones or divers.
Danish authorities said on Wednesday that a criminal investigation was underway to determine the cause of the rupture. Once that is complete, it is unclear how long it will take to repair the damage.
An official at a pipe-laying company in Europe said work could proceed only after safe conditions had been established, including by removing any gas or seawater from the pipeline.
Western sanctions placed on Russia may also complicate the cleanup and repair efforts because contractors may not want to do the work. In addition, Gazprom is no longer honoring business commitments and contracts, so it is not clear who would pay the costs.
Other pipelines to Europe may be vulnerable.
Even though Russia has throttled its exports, its natural gas is still flowing to Europe through Ukraine and other pipelines. If the war in Ukraine continues to go badly for Moscow, Gazprom could turn up the pressure by reducing these supplies.
A web of other pipelines from Algeria, Libya and Azerbaijan all sustain the economies of European countries and could be vulnerable to sabotage along their vast lengths. Whatever actor hit the Nord Stream pipelines might have been sending a message to Norway, which has replaced Russia as the large supplier of pipeline gas to the European Union. Norway is also a critical provider of gas to Britain.
It may not be a coincidence that a conduit from Norway to Poland known as the Baltic Pipe was opened on Tuesday. It was conceived to ease Warsaw’s dependence on Russia and passes close to where the leaks are.
Russia has attacked Ukraine’s energy infrastructure during the war.
Energy has become a battleground in the war over Ukraine. Mr. Putin has already shown that he is willing to junk business relationships with countries like Germany, which required decades to establish, in hopes of bending them to his will.
And, as the fighting has progressed, energy infrastructure in Ukraine has been repeatedly targeted by Russia.
After losing ground to a Ukrainian offensive this month, Russia unleashed a flurry of rocket and missile attacks on Ukrainian electrical power plants and the country’s electrical grid. Also this month, a Russian missile struck just over 300 yards from the South Ukraine Nuclear Power Plant, according to the Ukrainian state nuclear power company, Energoatom.
Throughout the summer, Ukrainian officials accused the Russian Army of targeting a stretch of high-tension electrical power lines connecting another nuclear complex, the Zaporizhzhia Nuclear Power Plant, to the Ukrainian electrical grid. They said the motive had been to deprive Ukraine of the plant’s electrical power.
Attacking pipelines could be another step along this road to energy warfare. “It is clearly an escalation of the conflict that is really scary,” said Mr. Rostand, the chief executive of Kayrros.
Stanley Reed reported from London, Reporting was contributed by Andrew E. Kramer from Kyiv, Ukraine; Melissa Eddy from Berlin; Christina Anderson from Bastad, Sweden; and Jasmina Nielsen from Copenhagen.