El Nino events reshape weather across the planet, driving floods, droughts and heatwaves far from the tropical Pacific where they are born. Research from the University of Tokyo's Graduate School of Science, by Tomoki Tozuka and graduate student Kaito Koike with Yoshikazu Sasai of the Japan Agency for Marine-Earth Science and Technology, delivers the first quantitative estimate of a surprising moderating influence: the ocean's phytoplankton.
These microscopic plants absorb sunlight near the surface, altering how heat is distributed through the upper ocean and hence how sea surface temperatures evolve. The team developed a new method for isolating the effect of phytoplankton on surface temperature and applied it within an ocean ecosystem model. The result: phytoplankton activity reduced the amplitude of El Nino events by about 40 percent.
Published in Environmental Research Letters, the finding argues that marine ecosystems are not passengers in the climate system but active participants in its most consequential oscillation. The authors note that their model simplifies complex ocean conditions and that testing under more realistic settings should refine the estimate. Incorporating such biological processes into prediction systems could nonetheless improve seasonal forecasts of extreme weather months in advance, with clear value for agriculture, water management and disaster preparedness.