For the duration of this cruise, we are hunters. Not for wildlife, not for the perfect photo, and not even for treasures. Our target might not be a living organism but it is just as elusive and, as we will find out, difficult to track : we are searching for methane flares.
Text and images: Marie Stetzler
For five months now I have been working with the software FlareHunter, analyzing acoustic imagery to identify methane bubbling from the seafloor. The time has now come to exchange the home-office-computer with a ship and hunt for them at sea! A first for me.
The plan was to first survey the west of Svalbard: this area is renowned for its exemplary flares and always a safe bet. This time again it didn’t disappoint us, and flares successively appeared on the monitor. But we wanted to explore a new area, and after the issue with the lander, we needed some exciting perspective. Years ago, colleagues had spotted some methane seepage in the southwest, an interesting clue to follow. Are those flares still active? Might there even be an entire undiscovered field of them? Equipped with our set of acoustic imagery instruments, such as echo sounders to investigate the seafloor, we set sail to the south to find out.
The reason why we track flares so eagerly is that methane is a greenhouse gas stored in the seafloor as temperature-sensitive hydrates (gas-containing ice), or as free gas in reservoirs within the sediment. In order for hydrates not to dissociate and free the methane, these ice-like structures need cold water and medium pressures, conditions found at over 350 m water depth with the temperatures found there. With changing bottom water temperatures nowadays though, we need to understand how the flare activity varies over time and space, and how much of it is reaching the atmosphere.
When we arrived at the south of Svalbard, we thoroughly investigated the area. As the ship is turning its survey rounds, the seafloor on the monitors stays surprisingly empty, as if they were too shy in our presence, except for some rare ones. It looks like a dead end…
The area is large and promising though, we keep our hopes up. After all, if our colleagues had sporadically spotted some by cruising through, why shouldn’t we after a thorough survey? We set course to the next indices, further south to western Bjørnøya. Now, regarding the flares, it’s “go big or go home”, literally.
Some small, flame-like shapes appear on the survey screen: flares, finally! Timid ones, that’s true, barely tens of meters high, unlike the almost-hundred meter beauties from the North, but it’s a good start. The exploration can continue, I’m relieved not having to set foot on land anytime soon and to discover some more seepage sites. All along the day flares continue to appear, proof that the area indeed shows some activity. Having this unexpected variability of methane emissions during the cruise compared to earlier ones shows us once more how inconstant flare activity can be, and will give us new insights on the driving factors of methane emissions.
To top it off, some less shy creatures came to sight from deck in the evening: a group of whales. Being able to do both flare hunting and whale watching in one day is what I call a good one.