In Memoriam: Liliane Merlivat, first Director of LODYC
It is with profound sadness that we learned of the death of Liliane Merlivat on June 8, 2026. Liliane Merlivat was an extraordinary scientist, driven by enthusiasm, curiosity, and insight. She was deeply passionate about geochemistry and climate studies, constantly pushing the boundaries of original experimental development and scientific analysis to better understand chemical, biological, and physical processes. With remarkable tenacity, she tackled numerous challenges across multiple fields, including isotope geochemistry, hydrothermalism, and CO₂ exchange at the air-sea interface. She naturally shared her passion with others, especially with young researchers, and her vivacity and scientific acumen inspired multiple generations, earning both respect and admiration for the relevance of her contributions.
A graduate of the École Supérieure de Physique et de Chimie Industrielles de Paris (ESPCI) in 1959, she joined the Commissariat à l’Énergie Atomique (CEA), where she founded and led the Isotope Geochemistry Laboratory in Saclay from 1983 to 1986. In 1986, she joined the French Center National of Scientific Research (CNRS) and contributed to the establishment of the Laboratoire d’Océanographie Dynamique et de Climatologie (LODYC – pronounced “L’Odyssée”), which she led from 1986 to 1998. Liliane and LODYC: the Iliad and the Odyssey. She continued her research at LODYC and later at LOCEAN, the successor laboratory of the LODYC in 2006. Until the very end, she remained deeply engaged with the laboratory’s activities, particularly her beloved CARIOCA buoys, the latest of which completed a fascinating journey in the Southern Ocean in 2022 and 2023*. Physically present at the LOCEAN laboratory until 2020, she always stayed abreast of the latest scientific developments. Even recently, she continued to remotely follow the laboratory’s weekly scientific meetings and seminars, which had been established at the creation of LODYC and to which she was deeply attached.
From her early work with Claude Lorius, she focused on the isotopic cycle of water, studying isotopic fractionation (deuterium, oxygen-18) during phase changes such as evaporation, condensation, and precipitation. Her research revealed how isotopic signatures in precipitation and ice cores (such as those from Vostok, Antarctica) reflect past climatic variations. This work paved the way for reconstructing temperatures over geological timescales.
In the 1970s, her expertise in measuring deuterium led her laboratory to be selected by NASA to analyze lunar samples from the Apollo program. Her discoveries about the signature of solar wind in lunar dust and the formation of deuterium through interaction with cosmic radiation expanded the horizons of cosmochemistry. She also contributed to the study of meteorites, revealing unprecedented isotopic ratios, such as in the Chainpur meteorite, where the deuterium-to-hydrogen ratio was six times higher than in Earth’s oceans.
It was during this period that she developed a passion for gas exchange at the air-sea interface, particularly for CO2. She conducted experiments in the air-water wind tunnel at IMST (Marseille) to understand the dynamical, physico-chemical processes controlling gas transfer. Years later, this work culminated in the Liss & Merlivat (1986) relationship, a global reference linking the gas exchange coefficient to wind speed, as well as the first global maps of gas transfer velocities derived from satellite wind speed data.
In the 1980s, Liliane Merlivat explored a new field: submarine hydrothermalism. Using helium-3 to helium-4 (3He/4He) ratios as a tracer, she participated in oceanographic campaigns, including aboard the R/V Jean Charcot on the East Pacific Rise. Her work helped locate active hydrothermal sites and led to the discovery of black smokers (hydrothermal vents at ~350 °C) in 1982. In 1984, she personally sampled these vents, contributing to the understanding of the relationship between heat flux and helium-3 flux emanating from magma. Her findings showed that the convective heat flux in the oceanic crust accounts for 10% of the total thermal flux at mid-ocean ridges.
She also contributed to the development of a high-precision analytical technique of tritium, an anthropogenic isotope used as a tracer for oceanic water masses. She encouraged her laboratory to develop methods for measuring freons in seawater, other anthropogenic tracers in the ocean.
Aware of the need to measure the partial pressure of seawater dissolved CO2 (pCO2) to quantify global CO2 fluxes, she developed, in collaboration with the ’Laboratoire de Géochimie des Eaux’ of the Paris 7 University, a spectrophotometric method for measuring pCO2 in the 1990s. She took the necessary steps to patent this method at the European level in 1993 and even approached industrial partners to commercialize the invention. This spectrophotometric method is used in CARIOCA buoys, autonomous drifting buoys capable of continuously measuring pCO2, temperature, fluorescence, and wind speed at the ocean surface. Deployed as part of numerous programs (such as POMME in the North Atlantic, Dyfamed in the Mediterranean, and CarboOcean in the Southern Ocean), these buoys not only enabled the estimation of air-sea CO2 fluxes in previously unexplored locations and periods but also allowed the study of various processes, such as the role of mesoscale structures and biological carbon production, rarely observed in the field. She always maintained a keen interest in pCO2 measurements from CARIOCA buoys and those from CARIOCA sensors installed on buoys from the PIRATA program, continuing to follow and comment on the results until very recently.
Liliane Merlivat received numerous awards, including Chevalier de la Légion d’Honneur in 2009 and the IFREMER Prize for Marine Science from the Académie des Sciences in 2015.
Tributes may be sent to Jacqueline Boutin, , who will share them with Liliane’s family.
More
*Naëck et al., Biogeosciences, 2025 ; news INSU sur :
https://www.insu.cnrs.fr/fr/cnrsinfo/retrait-precoce-de-la-glace-et-puits-de-co2-anormal-dans-latlantique-sud-en-ete-austral
Contact
Jean-Benoît Charrassin, director of LOCEAN
