Global Warming-Driven Decline in Phytoplankton Biomass in the Tropical Pacific Identified From Satellite Records

Phytoplankton biomass in tropical oceans is expected to decline because of global warming; however, there exists uncertainty because the satellite records for trend analysis are not long enough to overcome the interference of natural climate variability. Utilizing multiple regression models, we mitigated the influence of natural climate variability on trend analysis of satellite-derived chlorophyll-a (Chl-a, a proxy for phytoplankton biomass) in the tropical Pacific from 1997 to 2023, revealing a long-term Chl-a decline trend at a rate of approximately −0.4%/yr. Global warming contributed to the decline at a rate of −14.5%/°C. The tropical North Pacific (TNP) experienced a faster decline than the tropical South Pacific, which is highly related to asymmetrical hemispheric warming leading to enhanced sea surface warming and weakened trade winds in the TNP. This study provides robust estimates of the global warming-driven trend in tropical marine phytoplankton biomass, thereby contributing to predictions of future changes in marine ecosystems.