Somewhere on the East Siberian shelf, the sea stops looking like sea. Across a stretch more than a thousand metres wide, the surface seethes. In some places it only churns. In others the gas comes up as if out of a pipe, with a jacuzzi on top.
Igor Semiletov has spent thirty years working in the Arctic. He is a corresponding member of the Russian Academy of Sciences, heads the Arctic research laboratory at the Il'ichev Pacific Oceanological Institute, and leads a carbon laboratory at Tomsk Polytechnic University. His group calls these patches megaseeps. They know of about ten.
The numbers explain why that matters. In 2010 the group published a paper that put methane from the Laptev and East Siberian seas at 8 million tonnes a year. The IPCC's figure for the entire world ocean that year was 5 million. A later estimate, based on measurements and published more than ten years ago, said 17 million. Both numbers are old now, and the group says they are too low: they rest on what was known when they were made.
Since 2011 the group has been going back to the biggest seeps, as often as expeditions allow. They half expected the gas to rise for a while and then fall. It rose. One megaseep grew 4.5 times in four years, and its methane output grew by roughly the same factor.
Bubbles do not always reach the air. Some of the gas dissolves on the way up. The group measured that split too, and published it. The dissolved part is not lost: when storms churn and ventilate the water, it ends up in the atmosphere as well. Storms are not rare out there. In the Laptev Sea, where Semiletov says hurricanes had never been seen, the climate seems to have turned around 2010. Separately, a 2025 study in Ocean Science described the seafloor in the East Siberian Sea, about 46 metres down, warming by more than 3 °C after an Arctic cyclone mixed the water.
Then there is the rate at the strongest spots.
Some are just like a pipe, with a jacuzzi on top, a jacuzzi on top. And we have places … up to hundreds of kilograms per square metre per day. Hundreds of kilograms, not grams.
Есть вообще, как из трубы, там джакузи сверху, там джакузи сверху, и у нас есть места … до сотен килограммов с квадратного метра в сутки, сотен килограммов, не граммов.
— Igor Semiletov, Scientific Russia, 31:33
A single square metre, in a single day, gives off more than a person weighs. Now spread that over a field a kilometre wide.
One such field, measured and published in 2015, gives 1.5 million tonnes of methane a year. One field. Remember that the whole world ocean stood at 5 million tonnes in the IPCC's 2010 account.
The gas is old, too. In January 2026 Semiletov's group reported on a hotspot in the inner Laptev Sea in Communications Earth & Environment. Dissolved methane there reached 27,000 nanomoles per litre, up to 6000 times what the water would hold if it were in balance with the air. The surface was thick with bubbles. The methane's radiocarbon age was beyond the method's limit of 48,000 years. It was released from stores that had sat for millennia inside the permafrost under the seabed.
How many such places are there? More than 3000 gas discharge points on the shelf are already on the group's maps, and the weak ones are rarely revisited. The group chose to follow the megaseeps because it cannot afford to visit everything. Ten is the number Semiletov knows. What the group has seen so far, they say, is a needle in a haystack.
