Ocean biogeochemistry in the Canadian Earth System Model version 5.0.3: CanESM5 and CanESM5-CanOE

Abstract. The ocean biogeochemistry components of two new versions the Canadian Earth System Model (CanESM) are presented and compared to observations other models. CanESM5 employs same biology model as CanESM2, whereas CanESM5-CanOE (Canadian Ocean Ecosystem model) is a new, more complex developed for CMIP6, with multiple food chains, flexible phytoplankton elemental ratios, prognostic iron cycle. This described in detail outputs (distributions major tracers such oxygen, dissolved inorganic carbon, alkalinity, nitrogen cycles, plankton biomass, historical trends CO2 uptake export production) well CMIP6 Both models show gains skill relative which attributed primarily improvements circulation. shows improved most at depths. includes cycle, maintains high-nutrient/low-chlorophyll conditions expected regions (in CanESM2 CanESM5, limitation specified temporally static “mask”). Surface nitrate concentrations biased low subarctic Pacific equatorial Pacific, high Southern Ocean, both CanESM5-CanOE. Export production among lowest models; it highest, but rapid decline after about 1980. some ability simulate aspects community structure that single-species can not (e.g. seasonal dominance large cells) towards zooplankton detritus phytoplankton. Cumulative anthropogenic carbon dioxide through 2014 lower (122 PgC) (132 than observation-based estimates (145 or ensemble mean (144 PgC).