Mercator Ocean International’s expert oceanographers make new advances in the study of marine heatwaves

Several expert oceanographers in Mercator Ocean International’s team made important advances in the study of marine heatwaves (MHW), defined as extreme rises in ocean temperature for an extended period of time. Their scientific paper Decrease in air-sea CO₂ fluxes caused by persistent marine heatwaves has recently been published in Nature Communication, an open access journal that publishes high-quality research from all areas of the natural sciences.

CO₂ sensitive areas & Persistent Marine Heatwaves (PMHW)

Based on a joint analysis of satellite measurements, BGC-Argo observations, reconstructions derived from machine learning algorithms, and a state-of-the-art numerical model of the global ocean, produced by Mercator Ocean International, the study highlighted an absence of essential knowledge on marine heatwaves and their effect on the CO₂ sensitive areas. Starting from the latter, it has been observed that the ocean is currently absorbing about 25% of anthropogenic CO₂ emissions, thereby providing a significant ecosystem service to mankind by mitigating global warming. The CO₂ fluxes occur at different zones throughout the ocean: carbon dioxide is mainly absorbed at high latitudes, while it is released back to the atmosphere in low latitudes.

Marine heatwaves can occur at different locations in the ocean, and their magnitude and frequency have increased over the last couple of decades, with harmful impacts on ecosystems, marine industries and human activities. In the paper, the authors focused on intense and long-lasting marine heatwaves (Persistent Marine Heatwaves, PMHW). They show that PMHW occur in major CO₂ uptake and release areas, the so-called CO₂ sensitive areas, as shown in the picture below.

The strongest and most significant impact of PMHWs on the air-sea exchange of CO₂ occurs in the Pacific Ocean, with a net decrease in the oceanic uptake of CO₂ of 29 +/- 11 % in the North Pacific and a 40 +/- 9 % net reduction in CO₂ release in the Tropical Pacific.

Mechanisms leading to a reduction in the air-sea co2 flux density in the pacific during persistent marine heatwaves

These results provide new insights into the interaction between marine heatwaves and carbon dioxide sensitive zones. They especially pave the way for future investigations on its evolution under climate change.

The authors

They contributed to the article: Alexandre Mignot, Karina von Schuckmann, Peter Landschützer, Florent Gasparin, Simon van Gennip, Coralie Perruche, Julien Lamouroux & Tristan Amm.

Read the full paper