Climate pathways behind phytoplankton-induced atmospheric warming

• Published in: Biogeosciences
• Main Authors: Asselot, Rémy, Lunkeit, Frank, Holden, Philip B., Hense, Inga
• Other Authors: Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU]Sciences of the Universe [physics]; Sea ice
• Online Access: https://insu.hal.science/insu-03683307; https://insu.hal.science/insu-03683307/document; https://insu.hal.science/insu-03683307/file/bg-19-223-2022.pdf; https://doi.org/10.5194/bg-19-223-2022

International audience We investigate the ways in which marine biologically mediated heating increases the surface atmospheric temperature. While the effects of phytoplankton light absorption on the ocean have gained attention over the past years, the impact of this biogeophysical mechanism on the atmosphere is still unclear. Phytoplankton light absorption warms the surface of the ocean, which in turn affects the air-sea heat and CO 2 exchanges. However, the contribution of air-sea heat versus CO 2 fluxes in the phytoplankton-induced atmospheric warming has not been yet determined. Different so-called climate pathways are involved. We distinguish heat exchange, CO 2 exchange, dissolved CO 2 , solubility of CO 2 and sea-ice-covered area. To shed more light on this subject, we employ the EcoGEnIE Earth system model that includes a new light penetration scheme and isolate the effects of individual fluxes. Our results indicate that phytoplankton-induced changes in air-sea CO 2 exchange warm the atmosphere by 0.71 ∘ C due to higher greenhouse gas concentrations. The phytoplankton-induced changes in air-sea heat exchange cool the atmosphere by 0.02 ∘ C due to a larger amount of outgoing longwave radiation. Overall, the enhanced air-sea CO 2 exchange due to phytoplankton light absorption is the main driver in the biologically induced atmospheric heating.