Climate pathways behind phytoplankton-induced atmospheric warming

Rémy Asselot (1) , Frank Lunkeit , Philip B. Holden , Inga Hense

1 LOPS - Laboratoire d'Océanographie Physique et Spatiale

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 CO₂ exchanges. However, the contribution of air-sea heat versus CO₂ fluxes in the phytoplankton-induced atmospheric warming has not been yet determined. Different so-called climate pathways are involved. We distinguish heat exchange, CO₂ exchange, dissolved CO₂, solubility of CO₂ 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 CO₂ 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 CO₂ exchange due to phytoplankton light absorption is the main driver in the biologically induced atmospheric heating.

Domaines: Planète et Univers [physics]

Rémy Asselot, Frank Lunkeit, Philip B. Holden, Inga Hense. Climate pathways behind phytoplankton-induced atmospheric warming. Biogeosciences, 2022, 19, pp.223-239. ⟨10.5194/bg-19-223-2022⟩. ⟨insu-03683307⟩