The Arctic Ocean is a harsh working environment. That is why many of the scientific expeditions, are conducted in the summer and early autumn months, when the weather and the waters are more predictable. Most extrapolations regarding the amount of methane discharge from the ocean floor, are thus based on observations made in the warmer months.
"This means that the present climate gas calculations are disregarding the possible seasonal temperature variations. We have found that seasonal differences in bottom water temperatures in the Arctic Ocean vary from 1,7°C in May to 3,5°C in August. The methane seeps in colder conditions decrease emissions by 43 percent in May compared to August." says oceanographer Benedicte Ferré, researcher at CAGE Centre for Arctic Gas Hydrate, Environment and Climate at UiT The Arctic University of Norway.
Overestimation - Methane - Budget - August - Estimate
"Right now, there is a large overestimation in the methane budget. We cannot just multiply what we find in August by 12 and get a correct annual estimate. Our study clearly shows that the system hibernates during the cold season."
The study was conducted west of the Norwegian Arctic Archipelago Svalbard -- an area affected by a branch of North Atlantic Ocean current called West Spitzbergen Current. The observations were made at 400 meters water depth, where the ocean floor is known for its many methane seeps.
Bubbles - Methane - Seeps - Flares - Sounder
"We see bubbles from the methane seeps as flares during echo sounder surveys. There are plenty of them in this area. They probably originate from free gas migrating upwards from reservoirs, through sedimentary layers or tectonic faults." says Ferré.
The area in question is at the limit of so-called gas hydrate stability zone. Gas hydrates are solid, icy compounds of water and, often, methane. They remain solid beneath the ocean floor as long as the temperatures are cold and the pressure is high enough.
The bottom water...
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