Anthropogenic carbon emissions and associated climate change are driving; rapid warming, acidification, and deoxygenation in the ocean, which; increasingly stress marine ecosystems. On top of long-term trends, short; term variability of marine stressors can have major implications for; marine ecosystems and their management. As such, there is a growing need; for predictions of marine ecosystems on monthly, seasonal, and; multi-month timescales. Previous studies have demonstrated the ability; to make reliable predictions of the surface ocean physical and; biogeochemical state months to years in advance, but few studies have; investigated forecasts of multiple stressors simultaneously or assessed; the forecast skill below the surface. Here, we use the Community Earth; System Model (CESM) Seasonal to Multiyear Large Ensemble (SMYLE) along; with novel observation-based biogeochemical and physical products to; quantify the predictive skill of dissolved inorganic carbon, dissolved; oxygen, and temperature in the surface and subsurface ocean. CESM SMYLE; demonstrates high physical and biogeochemical predictive skill multiple; months in advance in key oceanic regions and frequently outperforms; persistence forecasts. We find up to 10 months of skillful forecasts,; with particularly high skill in the Northeast Pacific (Gulf of Alaska; and California Current Large Marine Ecosystems) for temperature, surface; DIC, and subsurface oxygen. Our findings suggest that dynamical marine; ecosystem prediction could support actionable advice for decision; making.
