The moon controls methane emissions in the Arctic Ocean

It may not be well known, but the Arctic Ocean is leaking massive amounts of the powerful greenhouse gas methane. These leaks have been going on for thousands of years, but could be amplified by a future warmer ocean. The potential of this gas to escape the ocean and contribute to the greenhouse gas budget in the atmosphere is a major mystery scientists are trying to solve.

The total amount of methane in the atmosphere has exploded in recent decades, and while some of the increase can be attributed to human activity, other sources are not very limited.

A recent article in Nature Communications even implies that the moon has a role to play.

Small pressure changes affect the methane release

The moon controls one of the most formidable forces in nature: the tides that shape our coastlines. Tides, in turn, have a significant impact on the intensity of methane emissions from the seafloor in the Arctic Ocean.

“We have found that gas accumulations, located in the sediments within one meter of the sea floor, are vulnerable to even slight pressure changes in the water column. Low water means less of this hydrostatic pressure and a higher intensity of methane release. High water equals high water. pressure and lower intensity of the release, ”said co-author of the article Andreia Plaza Faverola.

“This is the first time this observation has been made in the Arctic Ocean. It means that small pressure changes can release significant amounts of methane. This is a game changer and the biggest impact of the study,” said another co-author, Jochen Knies.

New methods reveal unknown release sites

Plaza Faverola points out that the observations were made by placing an instrument called a piezometer in the sediments and leaving it there for four days.

It measures the pressure and temperature of the water in the pores of the sediment. Hourly changes in the measured pressure and temperature revealed the presence of gas close to the sea floor that rises and falls as the tides change. The measurements were taken in an area of ​​the Arctic Ocean where no methane release has previously been observed, but where enormous gas hydrate concentrations have been sampled.

“This tells us that the release of gas from the seabed is more widespread than we can see with traditional sonar surveys. We did not see bubbles or gas columns in the water. Gas farmers with a periodicity of several hours will not be identified unless there is a permanent monitoring tool,” like the piezometer, ”says Plaza Faverola

These observations imply that the quantification of current Arctic gas emissions may be underestimated. However, high water appears to affect gas emissions by reducing their height and volume.

“What we discovered was unexpected and the implications are great. This is a deep-sea site. Small changes in pressure can increase gas emissions, but the methane stays in the ocean through the water depth. But what happens in shallower areas.” period can also be done in shallow Arctic waters. In shallow water, methane is more likely to reach the atmosphere, “says Knies.

Can counteract the temperature effects

A high sea level thus appears to affect gas emissions by potentially reducing their height and volume. The question remains whether sea level rise due to global warming can partially offset the effect of temperature on submarine methane emissions.

Earth systems are interconnected in a way that we are still deciphering, and our study reveals one of those interconnections in the Arctic: the Moon creates tidal forces, the tides generate pressure changes and bottom currents that in turn form the sea floor and affect methane beneath the sea floor. emissions. Fascinating! says Andreia Plaza Faverola

Provided by UiT The Arctic University of Norway