Text: Pavel Serov, CAGE.
We were not supposed to find gas hydrates (flammable ice-like crystals consisting of methane and water) in this CAGE cruise as the expedition objectives were slightly off gas hydrate topics. After 10-days, the long, all-consuming hunt for methane seeps and meltwater channels on the seafloor brought us to the very center of the Barents Sea.
Many factors have to coincide to form a shallow gas hydrate accumulation: the water depth should be large enough, the temperature should be low enough, there should be a strong supply of methane gas, and some soft sediments should be available to accommodate hydrate. It clicks when you realize that a point you are looking at on the map has it all. It certainly clicked that day when we found a group of seafloor mounds bursting gigantic flares of methane bubbles (figure) rising through the thick and cold layer of seawater. Hydrates.
Some hours later we found ourselves preparing a 1000 kg metal pipe (a gravity corer), which we hoped would pierce the methane-bursting mound and reveal its content. The first attempt did not bring us any touchable evidence for burning ice, but plenty of smell. A strong smell of rotten eggs, terribly unpleasant, but very useful indicator of methane on the seafloor. It was worth trying again. The second gravity corer was certainly not empty. Hydrates and bubbling degassing sediments were sticking out from the pipe. That’s what we hoped for!
It took minutes to seal the first gas sample and find a firecracker. One should prove that these white crystals are burning ice, and there is no better test than setting them on fire. After plenty of successful tests, it was time to retrieve the rest of the core from the protective plastic liner.
With the help of the Helmer Hanssen crew and a disk saw (totally safe) the rest of the bubbling mud and layers of beautiful white hydrate became available for public view.
Sampling hydrates is good fun – they burn, they make bubbles, they melt, they fizz, they blow up glass bottles if you seal a piece in it. But feeling that your predictions of where to find them were right is even better
Back in 2015, we proved for the first time gas hydrates in similar gas hydrate mounds (we call them pingos) in the western Barents Sea. It feels great to be a part of the team discovering another gas hydrate pingo field 5 years later. It means we have learned something about these methane-bursting beasts, we understand them better now. And we know how to find them.. – these were my last thoughts before falling asleep after a long shift on the hydrate day of the cruise.