Scientists say large amounts of methane may be trapped beneath the permafrost and could escape once it thaws. Research in Svalbard shows that methane is migrating beneath permafrost. Permafrost in lowland areas is rich in ice and snow, which can effectively trap methane, while upland areas with less snow and ice appear to be more susceptible to methane penetration. If permafrost thaws too much, greenhouse gas emissions can leak out, causing temperatures to rise further.
Millions of cubic meters of methane are trapped beneath Svalbard's permafrost, and scientists have now learned that methane can migrate and escape in the permafrost's cold storage. A massive escape could set off a warming cycle that would send methane emissions skyrocketing: Warming will thaw permafrost, causing more gas to escape, causing more permafrost to thaw, releasing more gas. Because Svalbard's geology and glacial history are very similar to those elsewhere in the Arctic, it is likely that these migrating methane deposits exist elsewhere in the Arctic.
"Methane is a potent greenhouse gas," said Dr. Thomas Birchall of the Svalbard University Center and lead author of the study in the journal Frontiers in Earth Science. "Currently, methane leakage from under permafrost is very low, but factors such as glacier retreat and permafrost melt may 'lift the lid' in the future.
Permafrost, a layer that remains below zero degrees Celsius for two or more years, is common in Svalbard. However, it is not uniform or continuous. Temperatures are higher west of Svalbard due to ocean currents, so the permafrost there is thinner and can be more patchy. Permafrost in the highlands is drier and more permeable, while permafrost in the lowlands is more wetted by ice. Rocks underground are often fossil fuel sources, and the methane released is trapped in permafrost. However, even within continuous permafrost, some geographical features can allow gas to escape.
The base of permafrost is difficult to study because it is inaccessible. However, over the years, companies searching for fossil fuels have drilled many wells into the permafrost. Researchers used historical data from commercial and research wellbores to map Svalbard's permafrost and identify areas of permafrost gas accumulation.
"My mentor Kim and I looked at a lot of historical wellbore data from Svalbard," Birchall said. "Kim noticed a recurring theme, which was the accumulation of gas at the bottom of the permafrost."
Heating the drilling mud to prevent the wellbore from freezing often affects the initial temperature measurement. But by looking at trends in temperature measurements and monitoring boreholes over time, scientists discovered the permafrost layer. They also looked at ice build-up in the wellbore, changes in cuttings produced while drilling, and changes in background gas measurements.
Wellbore monitors detected an influx of gas into the wellbore, indicating gas accumulation beneath the permafrost, and abnormal pressure measurements, suggesting the frozen permafrost was acting as a seal. In other cases, no gas is found even though the permafrost and underlying geology are suitable for capturing the gas and the rocks are known sources of hydrocarbons - suggesting that the gas produced has migrated.
Scientists stress that gas accumulations are much more common than expected. Of the 18 hydrocarbon exploration wells drilled in Svalbard, eight showed permafrost and half of them found gas accumulations.
Birchall said: "All drilling wells that encounter gas reservoirs are coincidental - by comparison, the success rate for hydrocarbon exploration wells specifically targeting reservoirs in more typical environments is well below 50 per cent. These situations appear to be common. Most recently in Longyearbyen An interesting example was a well being drilled near the airport. The drillers heard something bubbling in the well, so we decided to go take a look, and we brought a simple alarm that was used to detect the extent of the methane explosion - and when we placed the alarm above the wellbore, the alarm was triggered immediately."
Research by experts shows that as the climate warms, the active layer of permafrost - the upper one or two meters where it thaws and refreezes seasonally - is expanding. However, little is known about how deeper permafrost changes. To understand this, it is necessary to understand the flow of fluids beneath permafrost. If persistently frozen permafrost becomes thinner and more fragmented, methane will become more likely to migrate and escape, potentially accelerating global warming and exacerbating the climate crisis.
Compiled source: ScitechDaily