Scientists have discovered that methane from beneath the permafrost on the Svalbard archipelago may escape, putting it at risk from a warming cycle. Frequent methane accumulations found in wellbore studies highlight the potential for exacerbating global warming as permafrost melts. Image source: SciTechDaily.com
Scientists say large amounts of methane may be trapped beneath the permafrost and could escape if it melts.
Research in Svalbard shows that methane is migrating beneath the permafrost. While lowland areas have ice-rich permafrost that effectively seals the gas, upland areas with less ice appear to be more permeable. If permafrost melts too much, greenhouse gas emissions could escape, causing temperatures to rise further.
Millions of cubic meters of methane are trapped beneath Svalbard’s permafrost—scientists now know that methane can migrate and escape beneath the permafrost’s cold seal. The massive escape could create a warming cycle that causes methane emissions to skyrocket: Warming melts permafrost, causing more gas to escape, which melts more permafrost and releases more gas. Because Svalbard’s geology and glacial history are very similar to other parts of the Arctic, it is likely that these migrating methane deposits exist elsewhere in the Arctic.
“Methane is a potent greenhouse gas,” said the study’s lead author Dr. Thomas Birchall of the University Center of Svalbard. Frontiers of Earth Science. “Currently, leakage below the permafrost is very low, but factors such as glacier retreat and permafrost melt may ‘unveil’ this issue in the future.”
Liangku
Permafrost, ground that remains below freezing degrees celsius Lasting two years or more, it is common in Svalbard. However, it is not uniform or continuous. The climate is warmer in western Svalbard due to ocean currents, so the permafrost there tends to be thinner and possibly less intact. Permafrost in the highlands is drier and more permeable, while permafrost in the lowlands is more ice-saturated. The underlying rocks are often fossil fuel sources, releasing methane trapped in permafrost. However, even with continuous permafrost, certain geographical features can cause gases to escape.
The base of permafrost is difficult to study because of its inaccessibility. However, over the years, many wellbores have been sunk into the permafrost by companies looking for fossil fuels. Researchers used historical data from commercial and research wellbores to map Svalbard’s permafrost and determine the accumulation of permafrost gases.
“My supervisor, Kim, and I looked at a lot of historical well data in Svalbard,” Birchall said. “King noticed a recurring theme that kept coming up, which was the accumulation of gases at the bottom of the permafrost.”
Methane accumulation found
Heating the drilling mud to prevent the wellbore from freezing often affects the initial temperature measurement. However, long-term observations of trends in temperature measurements and monitoring boreholes allow scientists to identify permafrost. They also looked for changes in ice forming inside the wellbore, cuttings produced while drilling the wellbore, and changes in background gas measurements.
Wellbore monitors identified gas flowing into the wellbore, showing accumulation beneath the permafrost, and abnormal pressure measurements showed the icy permafrost was acting as a seal. In other cases, the gas is not present even though the permafrost and underlying geology are suitable for trapping the gas and the rocks are known sources of hydrocarbons – suggesting that the gas produced has migrated.
Unexpectedly frequent discoveries
Scientists stress that natural gas accumulations are much more common than expected. Eight of 18 hydrocarbon exploration wells drilled in Svalbard showed evidence of permafrost, and half of them found gas accumulations.
“Any wells that encounter gas accumulations are coincidental, compared to the success rate of hydrocarbon exploration wells that specifically target gas accumulations in more typical environments is well under 50 percent,” Birchall said. “These things look It’s very common. One anecdotal example is a wellbore that was recently drilled near Longyearbyen Airport. The drillers heard a bubbling sound coming from the well, so we decided to take a look, which was equipped to detect methane explosion levels. The basic siren, when we put the siren over the wellbore, the siren goes off immediately.”
Impact on climate change
Experts show that as the climate warms, the active layer of permafrost (the upper one or two meters that melts and refreezes seasonally) is expanding. However, we know little about how, if at all, deeper permafrost is changing. Understanding this depends on understanding fluid flow beneath permafrost. If persistently frozen permafrost becomes thinner and more uneven, this methane may migrate and escape more easily, potentially accelerating global warming and exacerbating the climate crisis.
Reference: “Gas lurks in permafrost in Norway’s Svalbard archipelago,” by Thomas Birchall, Malte Jochmann, Peter Betlem, Kim Senger, Andrew Hodson and Snorre Olaussen, October 30, 2023 Frontiers of Earth Science.
DOI: 10.3389/fear.2023.1277027
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