Jump to content

Methane from sea to air?

In recent years, researchers have observed that the amount of methane in the atmosphere increases. Methane is a greenhouse gas that contributes to global warming. A change in the natural methane emissions may cause the temperature to rise both higher and faster than previously thought.

Methane is the second most important greenhouse gas in the atmosphere, and emissions arise mainly from agriculture, rice paddies, landfills and heating. In addition, the gas is released from natural sources, such as animals, fires, wetlands – and the seabed.

From seabed to atmosphere

Senior scientist Cathrine Lund Myhre explains that scientists wonder whether emissions of methane from the seabed may be one source of the increased methane levels. Methane is stored as methane hydrates – an ice-like substance – under the seabed, and scientists know that methane gas leaks from these deposits and form bubbles that rise in plumes towards the surface.

Depending on the water depth, the bubbles may reach the ocean surface, or dissolve before the gas can enter the atmosphere. If the temperature of the sea rises, this may increase the methane discharge from the seabed to the sea, and thus contribute to a higher amount of methane reaching the atmosphere – with increased temperatures on Earth and in the ocean as a result.

MOCA: A research collaboration

To find out more about the relationship between methane hydrates on the ocean floor and methane levels in the atmosphere, the research project MOCA was created in 2013. The project is a collaboration between NILU, CAGE – Centre for Arctic Gas Hydrate, Environment and Climate at the University of Tromsø and CICERO Center for International Climate and Environmental Research.

The project runs for 3 ½ years, and during this time MOCA and CAGE will combine and coordinate measurements from ships, aircraft and on the seabed, as well as from the Zeppelin Observatory on Svalbard. The main purpose is to determine how much of the methane emitted from the ocean floor reaches up through the ocean and into the atmosphere. Furthermore, the results will be used to quantify the effects methane from gas hydrates in the seabed has on the atmosphere today, and what a potential change in these processes may mean for the climate in the future.

Scientific expeditions to the polar regions

The measurements started in the summer of 2014, and in mid-June the research vessel “RV Helmer Hanssen” from UiT left Tromsø for a six-week long raid, aiming to undertake marine and atmospheric measurements in the waters between Tromsø, Svalbard and the northern part of Svalbard. In the same region, CAGE is placing monitoring equipment on the seabed, to measure ocean currents, temperature and methane emissions.

In addition to this, flight campaigns are part of the project this year, to measure the methane concentration and variation in the atmosphere. The first plane took off in June 2014, and conducted research between Kiruna in Sweden and Longyearbyen on Svalbard, north of Svalbard and above wetlands in Sweden and Finland. This is in collaboration with the University of Cambridge. The second flight campaign takes place in Russia in late September to October, and will run from Novosibirsk, over Siberia and the wetlands there, and up to the area of the Kara Sea and Salekhard.

Screen capture of the onboard position system of the FAAM research aircraft BAe 146 during low altitude flight west of Svalbard. The ambitious raster flight track pattern initially planned included the points marked “D” in the figure. The mid-sized aircraft flew consistently at about 100 feet from the surface, reaching 50 feet when doing profiles. Thanks to the skill of the pilots, the reserve fuel was used to repeat the passages over the methane seeping area, doubling the amount of information collected. These measurements will be used with the results provided by the ship to assess the methane sea surface fluxes in the Arctic.
Del av flyvinge og båt på havet i bakgrunnen
The research vessel Helmer Hansen as seen from the window of the FAAM BAe 146 aircraft during one of the two over passes that took place on July 1st, 2014. All instruments were operational at that time, providing a point of comparison between air and ship borne data. These are the first simultaneous sea-air measurements of methane on the active emission spot located west of Svalbard.