Bérengère Dubrulle: understanding the mechanisms of turbulence

Bérengère Dubrulle's passion for the "infinite spaces that so frightened Pascal" was born during the holidays she spent with her grandparents in the Tarn, where she spent long evening stargazing. "For as long as I can remember, I’ve always wanted to understand what was above us, where we came from and how the solar system formed," the researcher recalls. This curiosity naturally led her to pursue scientific preparatory courses for competitive exams and enrol at the École Normale Supérieure.

During her studies, Bérengère Dubrulle spent a year at an astronomy laboratory in Berkeley, where the most advanced millimetric interferometer was located at the time. "That year, during which I was introduced to the experimental field by observing star-forming regions, helped me realise that I preferred theory over observation." Upon returning to France, she embarked on a PhD in astrophysics at the Toulouse Observatory, focusing on the subject of turbulence in the disks around stars. "For personal reasons, I then moved to Japan, where I took the opportunity to train in geophysics during a postdoctoral internship at a meteorology laboratory, where I worked on turbulence in the atmosphere." In 1992, she returned to France and joined CNRS where she continued her research on turbulence, initially concentrating on astrophysics.

Modelling turbulence in the formation of the solar system

"When I was recruited by CNRS, my objective was to propose a scenario for the formation of the solar system that incorporated turbulence, which was quite innovative," explains Bérengère Dubrulle. Her research focused on understanding the origin of turbulence, quantifying its action, its influence on the Earth's formation through the action of vortices. She also studied the structure of protoplanetary disks, their density and temperature distribution and developed a model for the dust sub-disk. "I also contributed to dynamo theory, demonstrating the influence of turbulence on the dynamo effect," adds Bérengère Dubrulle. Groundbreaking research that occupied her until 2000 when a family stay in Colorado prompted her to take a sabbatical.

The shift to the issue of climate change

"I used this stay to join the National Center for Atmospheric Research in Boulder which focused strongly on geophysics, the climate and the environment. As I had already had experience in this field in Japan, I decided to revisit atmospheric physics, where turbulence also plays a role." This experience made her aware of the urgency of climate issues and the significant need for improved modelling in this field. "It became clear to me that it was more important to work on modelling turbulence in the climate than in the formation of the solar system, so I decided to refocus my research on this area," the researcher explains. CNRS agreed that she could transfer from the CEA's astrophysics laboratory to which she was attached and join its neighbouring laboratory, the Condensed State Physics Service (SPEC – Univ. Paris-Saclay/CNRS/CEA), where she began a new chapter in her career.

Discovering the world of experimental research

At first, the transition was not easy. Coming from a theoretical background, especially in astrophysics, working with experimentalists, testing her theories against experimental results and seeing her models constrained by observations was a new challenge. "It opened up a dizzying and fascinating world full of challenges, especially as I arrived at a time when some surprising phenomena such as turbulent global bifurcations were being observed. These called into question certain aspects of turbulence theory for climate systems," explains Bérengère Dubrulle.

The researcher then began investigating sudden climate changes known as global bifurcations and focused on modelling them. "I worked on producing simple turbulence models using statistical physics, turbulence parametrisation or other simulation techniques to reduce the cost of the numerical calculations," she points out. From a more general perspective, she also endeavoured to verify the mathematical validity of equations describing the climate. Extensive research that earned her the CNRS silver medal in 2017 and saw her named as Female Scientist of the Year in 2022.

The change to engaged research

In addition to her research topics, Bérengère Dubrulle's approach to her research changed profoundly in the early 2000s.  "At that point, I realised that I needed to work on engaged research," confirms the researcher who surprised her colleagues when she decided to minimise her travel to avoid flying as much as possible. "The carbon footprint of research is far from insignificant, due to our instruments, digital simulations, etc. I believe that we have an ethical duty to align our commitments, our research topics and practices. That's what I have tried to do since my return from Colorado, even though, at the time, many didn't understand it," she adds.

The duty to educate

This commitment also extends to raising public awareness about the challenges of the climate issues covered by her research. She is the author of a youth novel entitled Le cercle des Carbophages (The Circle of Carbophages) published in 2007 and a book aimed at young readers Le climat: de nos ancêtres à vos enfants,  (The Climate: from our ancestors to your children), which she co-authored with Valérie Masson-Delmotte in 2003. "When I became aware of the climate crisis, I realised that if we wanted to change things, we had to start by educating our children. When I see the commitment of today's youth, it confirms that this was the right decision," highlights Bérengère Dubrulle.

Member of the French Academy of Sciences

A member of the French Academy of Sciences since 2023, Bérengère Durbulle is also a strong advocate for the role of women in science and the importance of interdisciplinarity. "Today, everyone talks about interdisciplinarity, but few people actually practice it and those who do are not necessarily recognised for it. However, it is essential to encourage interdisciplinary research, especially on societal issues, if we want to be able to meet the many challenges that lie ahead," concludes the researcher.
 

Bérengère Dubrulle (c)Sébastien Ruat CNRS Photothèque