Tuesday, May 17, 2022

Our moon controls the release of methane in the Arctic Ocean, study

It is the first time this observation has been made in the Arctic Ocean.

The Arctic region is one of the many natural sources of the greenhouse gas methane. Arctic methane emissions have been ongoing for thousands of years but could be intensified by a future warmer ocean.

However, understanding the gas emission phenomenon in the Arctic is partial, especially in deep environments where access is difficult, and hydro-acoustic surveys are sporadic.

Now, scientists from UiT The Arctic University of Norway suggest that the moon controls methane release in the Arctic Ocean. But how?

Scientists explain that the moon controls ocean tides, which significantly affects the intensity of Arctic methane emissions.

Co-author of the paper Andreia Plaza Faverola said, “We noticed that gas accumulations, which are in the sediments within a meter from the seafloor, are vulnerable to even slight pressure changes in the water column. Low tide means less of such hydrostatic pressure and higher intensity of methane release. High tide equals high pressure and lower intensity of the release.”

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

Scientists made the observations by using a tool called a piezometer. They placed the tool in sediments and left it there for four days.

The tool measured the pressure and temperature of the water inside the pores of the sediment. Hourly changes in the measured pressure and temperature revealed the presence of gas close to the seafloor that ascends and descends as the tides change.

The measurements were made in an Arctic Ocean area where no methane release has previously been observed but where massive gas hydrate concentrations have been sampled.

Plaza Faverola said, “This tells us that gas release from the seafloor is more widespread than we can see using traditional sonar surveys. We saw no bubbles or columns of gas in the water. Gas burps that have a periodicity of several hours won’t be identified unless there is a permanent monitoring tool in place, such as the piezometer.”

These perceptions suggest that the evaluation of present-day gas emissions in the Arctic might be disparaged. High tides, be that as it may, appear to impact gas outflows by decreasing their height and volume.

Knies said, “What we found was unexpected, and the implications are big. This is a deep-water site. Small changes in pressure can increase the gas emissions, but the methane will still stay in the ocean due to the water depth. But what happens in shallower sites? This approach needs to be done in shallow Arctic waters as well, over a longer period. In shallow water, the possibility that methane will reach the atmosphere is greater.”

Andreia Plaza Faverola said, “Earth systems are interconnected in ways that we are still deciphering, and our study reveals one of such interconnections in the Arctic: The moon causes tidal forces, the tides generate pressure changes, and bottom currents that in turn shape the seafloor and impact submarine methane emissions. Fascinating!”

Journal Reference:
  1. Nabil Sultan et al., Impact of tides and sea-level on deep-sea Arctic methane emissions, Nature Communications (2020). DOI: 10.1038/s41467-020-18899-3

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