Hexbyte Glen Cove Two months at sea to explore the Southern Ocean's contribution to climate regulation thumbnail

Hexbyte Glen Cove Two months at sea to explore the Southern Ocean’s contribution to climate regulation

Hexbyte Glen Cove

Credit: CC0 Public Domain

A team coordinated by two CNRS researchers and involving colleagues from Sorbonne University, Toulouse III–Paul Sabatier University, the University of Western Brittany and Aix-Marseille University, will traverse the Southern Ocean from January 11 to March 8, 2021, aboard the Marion Dufresne II research vessel chartered by the French Oceanographic Fleet. Their goal is to better understand the sequestration of atmospheric CO2 in the ocean, and especially how the chemical elements essential to this storage are supplied, transported and transformed by the ocean

The Southern Ocean, which surrounds the Antarctic continent, south of the Atlantic, Pacific and Indian Oceans, is a wild region that is difficult to explore. It plays a key, yet complex, role in the capture and storage of atmospheric CO2. A wide range of factors need to be taken into account, including biological activity (surface photosynthesis, carbon export to the deep ocean and its sequestration in sediments) and ocean circulation.

To understand these processes it is necessary to quantify them, which can be done by measuring what are known as geochemical elements (silica, nitrate, iron, zinc, as well as elements such as thorium, radium and rare earths). The vast majority of these tracers are present in minute concentrations in seawater.

The SWINGS1 oceanographic cruise, starting on January 11 and involving 48 scientists, is part of the international GEOTRACES program, which since 2010 has been constructing a chemical atlas of the oceans, compiling data describing the biogeochemical cycles of these trace elements and their isotopes in the world’s oceans. The data is acquired using very strict protocols, compared and validated among the different countries, and made available in an open database. This is the first time that such a comprehensive marine survey has been carried out in the Southern Ocean. Its goal is to determine the sources (atmospheric, sedimentary, hydrothermal, etc) of these elements, some of which (iron and zinc for example) play a crucial role in the photosynthetic activity of phytoplankton. The scientists will be studying their physical, chemical and biological transformations at all depths of the Southern Ocean, as well as their ultimate fate, when they sink into the deep ocean and are stored in sediments.

In addition to the SWINGS scientists, a team from OISO (Indian Ocean Observation Service), which is assessing the proportion of CO2 from anthropogenic emissions and the resulting ocean acidification, will embark on the Marion Dufresne II during the cruise. Another temporal data monitoring program, THEMISTO, will be studying open- ecosystems. Finally, a third project (MAP-IO) will use the Marion Dufresne II to carry out, among other things, physical measurements of the distribution of aerosols and trace gases. With these three projects complementing the SWINGS goals, scientific cooperation lies at the heart of the new cruise.

The laboratories involved in the SWINGS program are:

  • Laboratoire des Sciences de l’Environnement Marin (CNRS/IFREMER/IRD/Université de Bretagne occidentale)
  • Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (CNRS/CNES/IRD/Université Toulouse III—Paul Sabatier)
  • Laboratoire de Météorologie Dynamique (CNRS/ENS- PSL/ École polytechnique-Institut Polytechnique de Paris/Sorbonne Université)
  • Laboratoire d’Océanographie et du Climat : Expérimentations et Approches Numériques (CNRS/IRD/MNHN/Sorbonne Université)
  • Centre Européen de Recherche et d’Enseignement de Géosciences de l’Environnement (CNRS/INRAE/IRD/Aix-Marseille Université)
  • Laboratoire d’Océanographie Microbienne (CNRS/Sorbonne Université)
  • Institut Méditerranéen d’Océanologie (CNRS/IRD/Université de Toulon/Aix-Marseille Université)
  • Laboratoire Climat, Environnement, Couplages et Incertitudes (CNRS/CERFACS)
  • Technical Division of CNRS-INSU

The expedition was funded by France’s National Research Agency ANR, the French Oceanographic Fleet operated by the National Institute for Ocean Science IFREMER, the CNRS National Institute for Earth Sciences and Astronomy INSU, and the ISBlue University Research School.

Two months at sea to explore the Southe

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Hexbyte Glen Cove Studies explore fluids in pancakes, beer, and the kitchen sink thumbnail

Hexbyte Glen Cove Studies explore fluids in pancakes, beer, and the kitchen sink

Hexbyte Glen Cove

Credit: Pixabay/CC0 Public Domain

Mechanical engineer Roberto Zenit spent the summer of 2019 trying to solve a problem that now plagues science departments around the world: How can hands-on fluid dynamics experiments, usually carried out in well-stocked lab rooms, be moved off campus? Since the pandemic hit, leading researchers like Zenit have found creative ways for students to explore flow at home.

Zenit’s answer, ultimately, came down to pancakes. He teaches a lab class at Brown University, and one experiment requires students to measure viscosity, which is often done by measuring how quickly small spheres fall through thick liquids and settle at the bottom. But Zenit realized he didn’t have to do it that way. The kitchen is rich with viscous fluids, and all he had to do was pick one.

Why not pancake batter?

This fall, students in his class, wherever they were sequestered, had to mix up pancake batter, pour it on a horizontal surface, and measure how quickly the radius expanded. “By measuring the rate at which this blob grows in time you can back-calculate the viscosity,” said Zenit.

Zenit described the experiment during a mini-symposium on kitchen flows at the 73rd Annual Meeting of the American Physical Society’s Division of Fluid Dynamics. In addition to his viscosity-through-pancakes project, the symposium included new research on how fluids mix with each other and how they incorporate solid particles (as in batter or dough). Researchers from the University of Cambridge described new findings on hydraulic jumps—those eerily smooth circles of water, surrounded by turbulence, that form directly beneath a running kitchen faucet.

Chemical engineer Endre Mossige, a postdoctoral researcher at Stanford University, organized the symposium. “Kitchen flow experiments are so easy to do,” he said. “You need so little equipment to extract such useful information about dynamics.”

The kitchen is a natural place to look for inspiration, said Jan Vermant, an engineer at ETH Zurich. “In the kitchen we do a lot with high-interface materials,” he said. “You have to mix fluids and air and make emulsions, and work with bubbles. This is a fundamental problem of food projects, and one known by chefs all over the world.”

Vermant reported on his group’s recent work, which tackled a beer problem by turning it into a fluid dynamics problem. He studies thin films, and in recent research he’s been studying the stability of foam in beers and breads. Beermakers, he said, check on the fermentation progress of new brews by looking at the stability of foam. But, he said, the process is very “hand-wavy.” When he began looking at beer brewing through the lens of fluid dynamics, he found a rich research environment.

Beer bubbles contain a rich variety of environments: capillary flows, soap films, and protein aggregation. “Basically, they have all the mechanisms one can design as an engineer,” he said. His group found, to their surprise, that even though most beers have foam, different beers have different mechanisms behind those foams. Some foams act like soap films; others develop robust protein networks at the surface.

“They each highlight different aspects of the problem nicely,” said Vermant. In subsequent work, his group took a similarly close look at interfacial phenomena in breads—and similarly found a variety of behaviors. “They have this rich diversity of mechanisms to stabilize structures,” he said.

Vermant said the work isn’t just about beer and bread; it may also serve as inspiration for new materials. “We can mimic those systems and might make foams using the same principles as foams,” he said, which could be useful for applications ranging from spray insulation to protective foams for crops.

At Brown, Zenit said not every student successfully completed the experiment. “Some of them took my advice too literally, and did it in a hot pan,” he said. Cooking the pancake changed the viscosity—freezing the batter in place—which meant the students don’t have usable data. (But they did have breakfast.)

He said turning to pancakes during the pandemic has opened his eyes to different ways to teach fundamental ideas like viscosity. “In the regular experiments, you drop this sphere in a container and measure it,” he said. The fluid, he says, is reduced to its measurement. With batter, the student experiences the concept. “With the pancakes, you get to feel the viscosity.”

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