Alternate History: A Synthetic Ensemble of Ocean Chlorophyll Concentrations

Abstract

The ocean biosphere strongly influences biogeochemical cycling, carbon export, and air-sea carbon flux. Although phytoplankton constitute a relatively small reservoir of carbon, their ability to photosynthetically fix carbon from the atmosphere enhances the ocean's role as a carbon sink, allowing the ocean to store 45 times more carbon than the atmosphere (Friedlingstein et al., 2019). The efficiency and strength of the ocean biological pump can influence atmospheric carbon dioxide concentrations; in the absence of the ocean biosphere, atmospheric carbon dioxide concentrations would increase by approximately 50% of preindustrial values (McKinley et al., 2017).Internal climate variability plays an important role in the abundance and distribution of phytoplankton in the global ocean. Modes of internal climate variability, such as the El Niño Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the North Atlantic Oscillation (NAO), alter the physical and chemical environment for, and thus the abundance of, phytoplankton on timescales ranging from interannual to multi-decadal (