Methane from the sea

Researchers find elevated levels of the greenhouse gas above cracks in Arctic sea ice

Contact: John Ewald,  240-429-6127

The potent greenhouse gas methane is seeping out of parts of the Arctic Ocean, according to a new study recently published in Nature Geoscience, and the discovery may represent another cycle contributing to climate warming in the region.

Where the Arctic’s floating sea ice fractures to reveal open water, a team of researchers – including several from NOAA’s Earth System Research Laboratory (ESRL) – have measured elevated levels of methane.

Evidence suggests the gas comes from tiny bacteria and other organisms in the seawater, which release methane as a waste product, but this has not yet been demonstrated definitively.

The amount of methane moving from the Arctic Ocean water into the air is very small relative to the amount of methane that people pump into the atmosphere through activities such as natural gas development, livestock operations, and landfills, said James Elkins, Ph.D., a researcher with NOAA’s ESRL. But it is a surprisingly large amount compared with what scientists previously estimated for marine methane sources.

“And there is the potential for feedbacks,” Elkins said. “We know that Arctic sea ice is disappearing, and with warmer water, more sunlight, more breakup of the ice… we could see enhancement of the biological activity that creates methane.”

The new paper comes out of a multi-agency mission that probed Earth’s atmosphere, from pole to pole and surface to stratosphere, in a research airplane outfitted with atmospheric chemistry instruments.

The Nature Geoscience study also presents initial evidence that shallow water geological deposits, known as methane hydrates, are not currently sending substantial amounts of methane into the atmosphere. “We found no evidence of methane from hydrates,” Elkins explained.

Some scientists are concerned that the release of methane from hydrates and thawing permafrost could become self-reinforcing cycles in Arctic climate. More methane release could warm the region, creating more potential methane release, and more warming.

This study suggests that scientists interested in understanding global cycles of the potent greenhouse gas need to consider ocean surface sources more carefully, especially in the Arctic.

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