Methane venting through cracks in the sea ice
Arctic sea ice is actually a collection of smaller pieces that constantly shift, crack, and grind against one another as they are jostled by winds and ocean currents. Cracks, or leads, in the ice can open at any time of the year, but they are especially common during the spring and summer.
22 April 2012
Hippo search project data is available here.
The project was under the UCAR for research.
We report layers of increased methane concentrations near the surface ocean, with little or no enhancement in carbon monoxide levels, indicative of a non-combustion source. We further show that high methane concentrations are restricted to areas over open leads and regions with fractional sea-ice cover. Based on the observed gradients in methane concentration, we estimate that sea–air fluxes amount to around 2 mg d−1 m−2, comparable to emissions seen on the Siberian shelf. We suggest that the surface waters of the Arctic Ocean represent a potentially important source of methane, which could prove sensitive to changes in sea-ice cover.
During five Arctic fly overs with on board plane atmospheric monitoring instrument 'HIPPO' flights from 2009 to 2010, a research team observed increased methane levels while flying at low altitudes over the remote Arctic Ocean, north of the Chukchi and Beaufort Seas.
They located the source was cracks in Arctic sea ice and areas of partial sea ice cover. The cracks expose open Arctic seawater, allowing the ocean to interact with the air, and methane in the surface waters to escape into the atmosphere. The team detected no enhanced methane levels when flying over areas of solid ice.
The team detected no carbon monoxide in the atmosphere that would point to possible contributions from human combustion activities. It was extremely unlikely the methane was coming from high-latitude wetlands or geologic reservoirs.
"As Arctic sea ice cover continues to decline in a warming climate, this source of methane may well increase. It's important that we recognize the potential contribution from this source of methane to avoid falsely interpreting any changes observed in Arctic methane levels in the future." James Kort, research leader with the Keck Institute of Space Studies at the California Institute of Technology in Pasadena,
Atmospheric observations of Arctic Ocean methane emissions Kort et al Nature April 2012
ARCTIC OCEAN VENTING METHANE
It had always been assumed by climate change science that the shallow pools of Arctic methane in and below the Arctic continental shelves would not vent or escape through the water to the atmosphere because even if it were released (due to Arctic ocean warming) it would all be dissolved in the sea water. Russian research over the vast East Siberian Shelf was the first to disprove this by finding large local concentrations of methane in the air over the sea surface.