End-of-century Arctic Ocean phytoplankton blooms start a month earlier due to anthropogenic climate change

Phytoplankton net primary production in the Arctic has historically been constrained to a short, intense summer bloom that sustains fish, seabird, and marine mammal populations. However, climate change is altering Arctic phytoplankton bloom phenology. We use an ensemble of Earth system model simulations to isolate the impact of climate change on the timing, duration, and importance (relative contribution to total net primary production) of the bloom. Earlier blooms emerge across 71% of the Arctic Ocean by 2100, when blooms begin 34 days earlier and last 15 days longer than in 1970. Productivity is less concentrated in a single bloom in sub-Arctic seas and on Arctic inflow shelves by 2100, indicating that the bloom declines in importance. In contrast, bloom phenology and productivity exhibit only small changes by 2020. Our study demonstrates that anthropogenic climate change will greatly alter the timing and importance of the Arctic Ocean phytoplankton bloom by 2100.