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Nature_and_Environment.7

Global Climate Change

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{Nature_and_Environment.7.542}: Jay Hoffman {resist} Tue, 14 Jan 2020 00:16:37 CST (46 lines)

Climate gas budgets highly overestimate methane discharge from Arctic
Ocean

The atmospheric concentration of methane, a potent greenhouse gas, has
almost tripled since the beginning of industrialisation. Methane
emissions from natural sources are poorly understood. This is
especially the case for emissions from the Arctic Ocean.

The Arctic Ocean is a harsh working environment. That is why many
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.

"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."

How methane will react in future ocean temperature scenarios is still
unknown. The Arctic Ocean is expected to become between 3°C and a
whopping 13°C warmer in the future, due to climate change. The study
in question does not look into the future, but focuses on correcting
the existing estimates in the methane emissions budget. However:

"We need to calculate the peculiarities of the system well, because
the oceans are warming. The system such as this is bound to be
affected by the warming ocean waters in the future," says Benedicte
Ferré. A consistently warm bottom water temperature over a 12-month
period will have an effect on this system.

"At 400 meters water depth we are already at the limit of the gas
hydrate stability. If these waters warm merely by 1.3°C this hydrate
lid will permanently lift, and the release will be constant," says
Ferré.
"https://phys.org/news/2020-01-climate-gas-highly-overestimate-
methane.html?"

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