Marine Phytoplankton Extremes and Compound Extreme Events Have the Potential to Be Predicted Multiple Months in Advance

Abstract

Global marine primary producers, phytoplankton, are the base of the marine food web and vary on short timescales, characterized by seasonal blooms. There is growing concern about the occurrence of short‐term extreme events in phytoplankton abundance, which may impact higher trophic levels and economically‐important species. Previous work has investigated the occurrence and impacts of extremes, but forecasting of large‐scale extremes has not been attempted. Here, we leverage the Community Earth System Model Seasonal‐to‐Multiyear Large Ensemble (CESM SMYLE) to assess the potential predictability of phytoplankton extremes. We find that low phytoplankton biomass extremes (LBX) are significantly predictable up to 6‐month in advance. LBX are closely related to enhanced upper ocean stratification, which impacts nutrient availability. We find that compound events (LBX with marine heatwave and low oxygen extremes) are also significantly predictable up to 6 months in advance. These results could inform future model development with impacts for marine resource managers.