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Scientists have found evidence that frozen methane deposits in the Arctic Ocean, known as the “sleeping giants of the carbon cycle,” have begun to be released over a large area of the continental slope off the east coast of Siberia. The Guardian.
High levels of the potent greenhouse gas have been detected up to a depth of 350 meters in the Laptev Sea near Russia, raising concerns among researchers that a new climate feedback loop has been triggered that could accelerate the pace. of global warming.
Slope sediments in the Arctic contain a large amount of frozen methane and other gases, known as hydrates. Methane has a warming effect 80 times stronger than carbon dioxide for 20 years. The United States Geological Survey has previously listed the destabilization of Arctic hydrates as one of the four most serious scenarios of abrupt climate change.
The international team aboard the Russian research ship R / V Akademik Keldysh said that most of the bubbles were dissolving in the water, but methane levels on the surface were four to eight times higher than would normally be expected. and this was being vented to the atmosphere.
“Right now, it is unlikely that there will be a major impact on global warming, but the point is that this process has already been unleashed. This methane hydrate system on the eastern Siberian slope has been disturbed and the process will continue, ”said Swedish scientist Örjan Gustafsson, from Stockholm University, in a satellite call from the ship.
Fast guide
Methane and the Arctic
Why are methane hydrates considered ‘sleeping giants’ for the climate?
Scientists estimate that 1,400 gigatons of carbon are locked in underwater hydrates (frozen methane and other gases) under the Arctic’s underwater permafrost, some of which could be vulnerable to global warming. If large volumes were released, this could rapidly destabilize the climate because methane is a powerful greenhouse gas with a warming effect 80 times stronger than carbon dioxide over a 20-year period.
Such concerns led the United States Geological Survey to list the destabilization of Arctic hydrates as one of the four most serious scenarios for abrupt climate change. This possibility, sometimes referred to as the ‘clathrate gun hypothesis’, has been the basis for apocalyptic scenarios of runaway warming that tips the Earth towards a greenhouse state. However, several studies suggest that these fears are exaggerated.
That sounds scary. When could it happen?
There are many uncertainties: at what temperature will hydrates destabilize and, if they do, how quickly it will happen; And will the gas bubbles reach the surface and be released into the atmosphere or will they just dissolve in the oceans? These and other questions are now the subject of intense investigation on the shelf and slopes of the Laptev Sea and other areas of the Arctic.
The scientists, who are part of a multi-year International Platform Study Expedition, emphasized that their findings were preliminary. The scale of the methane emissions won’t be confirmed until they go back, analyze the data, and publish their studies in a peer-reviewed journal.
But the discovery of potentially destabilized frozen methane on slopes raises concerns that a new tipping point has been reached that could increase the speed of global warming.
The Arctic is considered ground zero in the debate over the vulnerability of frozen methane deposits in the ocean.
With the Arctic temperature now rising more than twice as fast as the world average, the question of when, or even if they will be released into the atmosphere, has been a subject of considerable uncertainty in climate computer models.
The 60-member Akademik Keldysh team believes they are the first to confirm by observation that methane release is already underway over a wide area of the slope some 600 km offshore.
At six monitoring points over a slope area 150 km long and 10 km wide, they saw bubble clouds released from sediment.
In a place on the slope of the Laptev Sea, at a depth of about 300 meters, they found methane concentrations of up to 1,600 nanomoles per liter, which is 400 times higher than what would be expected if the sea and the atmosphere were in equilibrium.
Igor Semiletov of the Russian Academy of Sciences, who is the chief scientist on board, said the discharges were “significantly larger” than anything encountered before. “The discovery of the active release of platform slope hydrates is very important and unknown until now,” he said. “This is a new page. They can potentially have serious climatic consequences, but we need more studies before we can confirm that. “
The most likely cause of the instability is an intrusion of warm Atlantic currents into the eastern Arctic. This “Atlantification” is driven by human-induced weathering.
The latest discovery potentially marks the third source of methane emissions in the region. Semiletov, who has been studying this area for two decades, previously reported that gas is being released from the Arctic shelf, the largest of all seas.
For the second year in a row, his team has found crater-shaped pox marks in the shallower parts of the Laptev Sea and the East Siberian Sea that are discharging jets of methane bubbles, reaching the sea surface at levels of tens to hundreds of times higher. than normal. This is similar to the craters and sinkholes recorded in the inner Siberian tundra earlier this fall.
Temperatures in Siberia were 5 ° C higher than the average from January to June this year, an anomaly that was at least 600 times more likely due to human-caused emissions of carbon dioxide and methane. Last winter’s sea ice melted unusually early. This winter’s frost hasn’t started yet, it’s already a later start than at any other time on record.
