A climate mission at sea off the coast of Brazil

Natacha, you're a master's student in physics at Sorbonne University. How did you get involved in this adventure?

Natacha Kaminski: I was interested in oceanographic research and had done my third-year internship at the Oceanographic and Climate Laboratory (Laboratoire d'Océanographie et du Climat (LOCEAN)) and, during my university career, I chose options in oceanography. At the "Campus océan" forum organized by the Ocean Institute at Sorbonne University in October 2022, I stopped by the stand of the Paris Earth Science Institute (Institut des Sciences de la Terre de Paris (ISTeP)), which was exhibiting a core of sediment from the ocean floor. They were looking for a student intern. I took the plunge, was accepted as an intern and was given the opportunity to spend a month on mission for the first part of the Amaryllis-Amagas offshore voyage.

Jeffrey, what are the objectives of this offshore campaign?

Jeffrey Poort: This Franco-Brazilian mission, led by two marine geoscientists, Sébastien Migeon, professor at Sorbonne University, and Daniel Praeg, Géoazur researcher, brings together the ISTeP and LOCEAN laboratories in collaboration with twenty French, Brazilian, German and Swedish laboratories and universities.

Its goal is to study the major but uncertain role played by the Amazon region in the Earth's climate system. Its role as a terrestrial carbon sink depends on processes that are still poorly understood, such as the intensity and distribution of continental precipitation, the fertilization of soils by Saharan dust, and the potential instability of gas hydrates—pockets of frozen water that form within layers of sediment and contain gas molecules.

Why study the Amazon region in particular?

J. P.: C

This region is emblematic of current climate disruptions, and the Amazon River has the world's largest sediment flow. Many geophysical processes are taking place in its delta. One of these concerns potentially unstable gas hydrates. A sharp rise in temperature or pressure will cause the solid elements trapped in the sediment layers to turn back into gas, which will try to escape to the surface. This can weaken the cohesion of sediments and generate gigantic submarine landslides that can trigger tsunamis.

With rising sea levels likely to increase pressure, and warmer waters, it is conceivable that the instability of gas hydrates will increase, leading to more submarine landslides and more disasters.

It is therefore important to study the sediments deposited along the equatorial margin of South America to find traces of these landslides and better understand their link with changes in regional and global climatic conditions.

What was your daily life like on board for almost a month?

N. K.: Technicians, students, crew members—there were around a hundred of us on board the Marion Dufresnes, including 38 scientists. Each scientific team worked in shifts, with each group taking turns to work four hours in the morning and four hours in the afternoon. As for me, I was mobilized from four to eight o'clock and from four to eight o'clock on scientific activities. Outside these slots, we could get together to play badminton, board games, table soccer or go to the gym. The boat is a special place, because we have time to talk and exchange ideas with like-minded people from all over the world. And we were lucky enough to do this mission in exceptional conditions, as the boat was not full and we each had an individual cabin, with shower and toilet.

J. P.: Which is quite rare. It's usually more spartan! I've been on some thirty campaigns at sea, and this is the first time I've sailed on a boat as big and comfortable as the Marion Dufresne. 

What scientific activities did you carry out on board?

N. K.: We were mainly concerned with the sediment cores recovered by Calypso, one of the few corers in the world capable of collecting cores over 60 meters long. The longer the core, the further back in time it can be traced. This means we can study climatic variations in the region as far back as several million years.

One of our tasks was to cut the cores into 1.5-meter sections, then analyze their density and scan them. Then we had to cut these sections in half. Once open, the sedimentology team would describe the strata and take photos. It's a huge job, which we try to do as much as possible on board while the sediments are still intact.

At the same time, we measured heat flows by fitting thermometers to the corer, and once the core was on board, we used a needle to analyze how heat propagates in the sediments.  The technicians were also in charge of checking all the measuring instruments.

Jeffrey, what next for this campaign?

J. P.: One month's collection represents several years' work. All the material collected will be studied, and in a year's time we'll get together to take stock of our progress. Later, these analyses will be used to create models linked to climate change, and will undoubtedly feed into future IPCC reports.

Natacha, will you remember most about this mission?

N. K.: It's been the best experience of my life. I didn't expect it at all. As it was my first mission at sea, I discovered a lot about how we are organized to keep the boat operational. I loved the friendly atmosphere on board. The ship is like a bubble out of time. Even if we don't sleep much, we share a privileged moment, a parenthesis at sea.