Home Sciences Methane leaks spread in arctic seas

Methane leaks spread in arctic seas

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New expeditions have discovered huge flows of methane in the seas of East Siberia and the Laptev Sea, amplifying the flows of methane flowing off the coast, while the warming of the Arctic continues to skyrocket.

New expeditions have discovered numerous areas of bubbling methane flow on the shelf of the Laptev Sea (which extends along the eastern coast of Siberia, the Taimir Peninsula, the Northland and the New Siberian Islands) and in the Siberian Sea. Eastern, a marginal sea of ​​the Arctic Ocean. Researchers believe that these methane flows enhance the warming of the Arctic, as they explain in a study published in the journal Marine and Petroleum Geology.

These expeditions revealed large new methane seeps in the East Siberian and Laptev seas, with bubbling flows of methane from the seepage areas rising through a 45 m thick water column and reaching the sea surface. , as reported in a statement.

The research data shows that the East Siberian Sea, the Laptev Sea and the Kara Sea (a sector of the Arctic Ocean located north of Siberia), have thawed (ice-free) upper sediment layers.

sediment without ice

The sediments do not have ice because their temperatures on-site are at least 0.6 °С above the freezing point. The difference between the temperature on-site and the freezing point is higher on the continental slope of the Laptev Sea (up to 2.5 °С) and on the inner shelf, exposed to the effect of heat columns of large rivers. The salt water from the sea mixes there with the fresh water from the river, the salinity of the sea water decreases and its freezing point increases, the researchers explain.

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This effect can lead to up to 3°C warming of near-bottom water and surface sediments in the shallow waters of the East Siberian Sea shelf, warn the researchers, who sampled bottom sediments at 110 sites. .

In addition, multi-annual data obtained from all stations show that, in the near-shore area, the mean annual temperature of the bottom water has increased by 0.5°C during 1999–2012, while in summer this increase reaches >1 °C The researchers believe that this warming of the water may be due to the increasing discharge of the Lena River, one of the major rivers in northern Eurasia.

Not just temperatures

The authors of these expeditions also discovered that methane anomalies are not always accompanied by higher temperatures in the bottom sediments, indicating that the phenomenon is more complex.

Although methane anomalies were found in patches of warmer bottom sediments on the northern Laptev shelf, there were no temperature increases in areas of massive methane seepage on the East Siberian shelf.

The researchers attribute this to thicker subsea permafrost and younger seepage ages, two factors that also influence methane fluxes.

The East Siberian Arctic shelf contains approximately 80% of the Earth’s underwater permafrost and has huge reserves of methane hydrates (CH 4 ), which are methane molecules contained in structures of water molecules.

Under conditions of pressure and temperature that exist in the continental slope and in the polar regions (permafrost), these molecules become solid crystalline substances (methane ices).

also salinity

The stability of these hydrates so that methane does not escape into the atmosphere depends on the state of the submarine permafrost, mainly on the temperature and salinity in the system.

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The point is that the thermal state of subsea permafrost is now approaching, and in some regions has already reached, the melting point. These processes have led to an increased release of methane from the destabilized hydrates into the atmosphere, the researchers note.

In 2010, scientists further discovered that frozen methane deposits in the Arctic Ocean had begun to release over a large area of ​​the continental slope off the coast of Eastern Siberia.

The authors of the new research reveal that this process has been enhanced in recent years and think that the rate of warming in the Arctic has been caused by the reduction in the occupied surface and thickness of the ice of the Arctic Ocean, of the layer of ice from Greenland and other island glaciers.

Galloping heating

Global warming is a major concern, and the Arctic attracts special attention: recent analyzes show that the climate in the region is warming 3 to 4 times faster than the global average.

Since the start of the industrial revolution in the 19th century, the Earth has warmed by around 0.8°C, while the Arctic has warmed by 2-3°C over the same period.

Arctic warming reached 2°C in 2005 and 4°C in 2018, exceeding the most pessimistic predictions for the year 2100 foreseen in the Paris Agreement.

Reference

In-situ temperatures and thermal properties of the East Siberian Arctic shelf sediments: Key input for understanding the dynamics of subsea permafrost. E. Chuvilin et al. Marine and Petroleum Geology, Volume 138, April 2022, 105550. DOI:https://doi.org/10.1016/j.marpetgeo.2022.105550

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