North Atlantic - over the past 30 years, the amount of human-generated carbon stored in the ocean has increased by more than 30%
On 9 June, some 40 French and Spanish scientists and sailors will board the French Oceanographic Fleet’s vessel L’Atalante for the OVIDE 2026 mission, between Greenland and Portugal. Coordinated by Ifremer, with the support of IRD, CNRS, the University of Western Brittany (UBO), the Spanish National Research Council (CSIC), and Durham University, this international programme has been monitoring changes in the North Atlantic - a key region in global climate regulation - for over twenty years. Recently, an international study led by the Laboratory of Physical and Spatial Oceanography (CNRS, Ifremer, IRD, UBO) and published in the journal Biogeosciences revealed that the amount of anthropogenic carbon stored in the North Atlantic has increased by more than a third on average over the past 30 years.
At the initiative of the Laboratory of Physical and Spatial Oceanography (LOPS), the OVIDE programme —“Observatory of Interannual to Decadal Variability in the North Atlantic”- has been monitoring the evolution of the AMOC (Atlantic Meridional Overturning Circulation), the Atlantic current loop that connects surface and deep waters, for the past 24 years. Comparable to a giant “conveyor belt,” this current system transports warm waters containing, anthropogenic carbon and nutrients from the equator northward, while cold, deep waters circulate southward. The AMOC plays a key role in regulating Europe’s climate and in the ocean’s ability to absorb and store a large portion of the CO₂ emitted by human activities.
Since the start of the Industrial Revolution in approximately 1760, 2.6 trillion tons of CO₂, equivalent to the cumulative emissions of 560 billion cars, have been released into the atmosphere, primarily through the burning of fossil fuels, cement production, deforestation, and changes in land use. Today, the global ocean absorbs about 90% of the excess heat accumulated in the climate system due to greenhouse gas emissions and more than a quarter of anthropogenic CO₂ emissions. But this absorption is not uniform: the North Atlantic alone accounts for about 30% of global annual anthropogenic carbon uptake and hosts the largest reservoir of this carbon per unit area, largely sustained by the AMOC.
The 2026 edition of the OVIDE campaign takes place against an unprecedented backdrop: the years 2023 to 2025 saw record-breaking surface temperatures in the North Atlantic, raising numerous questions about the potential consequences for ocean currents, the uptake and storage of anthropogenic carbon, and marine ecosystems.
The data collected will help us understand how recent record-breaking heat events propagate into the deep ocean and assess changes in ocean currents and carbon storage in the North Atlantic. “Thanks to these measurement series conducted every two years since 2002, we can distinguish natural variations from trends linked to climate change,” explains Pascale Lherminier, an oceanographer at Ifremer and mission leader for OVIDE 2026. “Only such regular, long-term series can reveal significant trends and account for the effects and reality of climate change.”
Oceanographic expeditions are essential because they provide physical and biogeochemical reference data across the entire water column, from the surface to the deep ocean. These highly precise data allow us to calibrate data acquired by ocean observation networks such as Argo, OceanSITES, and satellite observations. These tools are complementary and essential for gaining a comprehensive understanding of the state and evolution of the ocean in the face of climate change, adds Lidia Carracedo, a researcher at Ifremer, coordinator of the OVIDE programme, and co-mission leader for OVIDE 2026.
On board, researchers will measure ocean temperature, salinity, oxygen, total alkalinity, and acidity (pH) from the surface down to a depth of 5,550 meters. Seven autonomous “Argo Deep” floats will also be deployed to continue observations after the mission.
For the first time, OVIDE will also include a new paleo-oceanographic component aimed at improving the reconstruction of the past evolution of Atlantic Ocean circulation (AMOC) through the observation of marine microorganisms called foraminifera.
The amount of anthropogenic carbon stored in the North Atlantic has increased by more than a third over the past 30 years
The mission’s launch comes as a new scientific study from the OVIDE program was recently published in the journal Biogeosciences. This research sheds new light on carbon dynamics in the subpolar North Atlantic over the past thirty years.
This study reveals that the amount of carbon from human activities stored in the North Atlantic has increased by more than a third over the past 30 years, driven by the continuous rise in atmospheric CO₂. This carbon is now reaching the deepest layers of the ocean.
The results show that the growing accumulation of anthropogenic carbon is the primary indicator of its increased northward transport by the Atlantic Meridional Overturning Circulation (AMOC). This clear and robust signal indicates that the North Atlantic is absorbing and storing more and more anthropogenic carbon over the long term, despite decadal variations in the intensity of the AMOC, which can modulate this transport by about 25%.
According to scientists, however, the ocean’s capacity to absorb CO₂ could be compromised if ocean circulation were to slow down permanently as a result of climate change.
“Our results show that the variations observed today are primarily linked to carbon produced by human activities. Understanding how the ocean absorbs and redistributes this carbon is essential for anticipating future climate change. This is a major scientific and societal challenge,” the study’s authors emphasise.
Read the scientific publication: Bajon, R., Carracedo, L. I., Mercier, H., Asselot, R., and Pérez, F. F.: Seasonal to long-term variability of natural and anthropogenic carbon concentrations and transports in the subpolar North Atlantic Ocean, Biogeosciences, 23, 2335–2363, https://doi.org/10.5194/bg-23-2335-2026, 2026.