Impact of El Ni?o Variability on Oceanic Phytoplankton

摘要

Oceanic phytoplankton respond rapidly to a complex spectrum of climate-driven perturbations, confounding attempts to isolate the principal causes of observed changes. A dominant mode of variability in the Earth-climate system is that generated by the El Ni?o phenomenon. Marked variations are observed in the centroid of anomalous warming in the Equatorial Pacific under El Ni?o, associated with quite different alterations in environmental and biological properties. Here, using observational and reanalysis datasets, we differentiate the regional physical forcing mechanisms, and compile a global atlas of associated impacts on oceanic phytoplankton caused by two extreme types of El Ni?o. We find robust evidence that during Eastern Pacific (EP) and Central Pacific (CP) types of El Ni?o, impacts on phytoplankton can be felt everywhere, but tend to be greatest in the tropics and subtropics, encompassing up to 67% of the total affected areas, with the remaining 33% being areas located in high-latitudes. Our analysis also highlights considerable and sometimes opposing regional effects. During EP El Ni?o, we estimate decreases of -56 TgC/y in the tropical eastern Pacific Ocean, and -82 TgC/y in the western Indian Ocean, and increase of +13 TgC/y in eastern Indian Ocean, whereas during CP El Ni?o, we estimate decreases -68 TgC/y in the tropical western Pacific Ocean and -10 TgC/y in the central Atlantic Ocean. We advocate that analysis of the dominant mechanisms forcing the biophysical under El Ni?o variability may provide a useful guide to improve our understanding of projected changes in the marine ecosystem in a warming climate and support development of adaptation and mitigation plans.