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Methane measurement cruise

Foto: Adam Durant

The week before Easter NILU scientists Adam Durant and Ove Hermansen are on board the research vessel “RV Helmer Hanssen” of UiT – The Arctic University of Norway, as part of the MOCA project. The purpose of the trip is to install and test for measuring methane in the atmosphere over the Arctic Ocean, in preparation for a summer campaign to determine if gas emissions from methane hydrates at the ocean floor are reaching the atmosphere. Follow the vessel here.

Methane is stored in subsea permafrost and marine sediments, in the form of methane hydrates – an ice-like substance. If the temperature rises, methane gas may leak 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.

Testing equipment

Together with representatives from partner CAGE – Centre for Arctic Gas Hydrate, Environment and Climate at UiT, Adam Durant and Ove Hermansen are spending the week aboard the research vessel RV Helmer Hanssen. They are going to install a Picarro cavity ring down spectrometer, and a flask sampling apparatus to collect gas samples for isotopic analysis.

– This week is all about installing and testing the equipment, explains Adam Durant and expedition leader Stefan Buenz from CAGE, – but come June we will begin a series of ship campaigns and intensive measurements. The instruments on board the ship will be used to capture atmospheric signals. These signals indicate if methane is present at levels above background at the ocean surface that could potentially be related to methane seeping from the ocean floor and up through the water column.

The measurements taken on the ship are collected as air samples from the sea surface directly above known methane bubble plumes emitted from the ocean floor. Air is drawn in through an intake on a high point on the ship and down to the instruments. Besides methane, measurements of carbon dioxide, carbon monoxide, ethane and different isotopes are made – the latter to identify isotopic signatures, which can show where the measured air mass originated.

– Data is transmitted continuously from the ship to NILU via satellite, says Durant. – We want to be able to follow the measurements from NILU as well. If everything goes to plan, we and our partners from CAGE will be ready to embark on the first MOCA ocean research cruise in June.

On land, at sea and by air

Scientists assume that methane hydrates from the sea floor can be a potential source of methane in the atmosphere, and that changing ocean temperature might change the methane flux. Released into the atmosphere, methane can act as a powerful greenhouse gas, which may contribute to more rapid climate warming.

The MOCA project and CAGE (see fact box) aims to combine and coordinate subsea, marine and aerial measurements to determine how much of the methane gas emitted that seeps up through the ocean and into the atmosphere. From June to August, RV Helmer Hanssen and her crew of 30 will follow pre-set routes in the waters between Tromsø, Svalbard, and north of Svalbard making atmospheric measurements directly over known methane seep sites.

In the same region, CAGE and the MOCA project are placing monitoring equipment directly on the seabed. This equipment will measure ocean currents, temperature and methane emissions. In addition, flight campaigns will be conducted in parallel to capture the methane concentration in the atmosphere, explains senior scientist and project leader of MOCA, Cathrine Lund Myhre.

– We have seen an increase of methane in the atmosphere over the past 6-7 years, Myhre says, – and we need better knowledge about where it comes from and the potential future climate effects it entails in an increasingly warmer climate. Perhaps part of the answer lies in the depths of the sea?

Relevant links:

The MOCA-project: http://moca.nilu.no

The University of Tromsø/CAGE: http://cage.uit.no/

CICERO Senter for klimaforskning: http://www.cicero.uio.no/home/