Warning of methane blasts in Kara Sea adjacent to Yamal craters caused by gas eruptions associated with melting permafrost due to global warming.
Huge attention has focused on the mysterious large holes that have suddenly appeared in the Siberian Arctic recently, and now there is evidence of a similar process underwater in southern areas of the Kara Sea.
Large mounds - described as pingos - have been identified on the seabed off the Yamal Peninsula, and their formation is seen as due to the thawing of subsea permafrost, causing a 'high accumulation' of methane gas.
These mounds 'are leaking methane' and their 'blowout potential' poses a significant 'geohazard' to energy exploration in Arctic waters, according to new research by scientists at Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) in Norway, supported by the Federal Subsoil Resources Management Agency of Russia.
For example, in a little-reported incident 20 years ago, during 'geotechnological drilling' by Russian vessel Bavenit in the Pechora Sea, a pingo gas deposit was opened, threatening the ship's safety with a sudden methane release.
Dr Pavel Serov, lead author of the research which is published in the Journal of Geophysical Research, said: 'Pingos are intensively discussed in the scientific community especially in the context of global climate warming scenarios. They may be the step before the methane blows out.' The researchers focused on 'two subsea pingos that were identified offshore (of) the very same area of the mysterious Yamal peninsula craters', reported the CAGE website.
The Norwegian study 'shows how important methane accumulation is for the formation of subsea pingos'. These structures are 'now found strewn on the ocean floor in the Arctic shallow seas', according to the research by CAGE, part of UiT The Arctic University of Norway. 'The study area lies in the shallow South Kara Sea, at approximately 40-metre water depth.'
The underwater mounds were between 70 metres and 1,000 metres in diameter, and had been spotted originally on a seismic study of the area. They rise between five and nine metres above the surrounding sea floor. In overall size they are considerably larger than those found on land in Yamal.
Dr Serov said: 'Our question was: Are these mounds submerged terrestrial pingos? Or are they something different forming under marine conditions? One of the South Kara Sea pingos was leaking a lot of methane but where was the methane coming from?'Initially it was thought the undersea pingos were 'relics of the Ice Age', but the groundbreaking new research indicates the reverse, indicated CAGE director Professor Jurgen Mienert, a co-author of the paper. 'The CAGE study shows these newly discovered subsea pingos may be quite recent.'
Crucially, 'gas leakage from one of the ocean floor pingos offshore (of) Siberia shows a specific chemical signature that indicates modern generation of methane', state the researchers. 'We suggest that the mound formed more recently, moving material physically upwards.' Likewise the processes leading to methane eruptions on the neighbouring peninsula are seen as very recent.
Location of Pingo-like Features (PLF)The researchers warned:
'For petroleum companies these areas may pose a geohazard. Drilling a hole into one of these subsea pingos, can be not only expensive but also catastrophic. During a geotechnical drilling in the close by Pechora Sea, an industry vessel unknowingly drilled a hole into one of these mounds. It triggered a massive release of gas that almost sunk the vessel.'This is believed to refer to an incident in 1995 involving the Bavenit, west of Vaygach Island in the Pechora Sea. Dr Serov stated: 'We don't know if the methane expelled from the subsea pingos reaches the atmosphere. But it is crucial that we observe and understand these processes better, especially in shallow areas, where the distance between the ocean floor and the atmosphere is short.'