The recently developed Norwegian Earth System Model (NorESM) is employed forsimulations contributing to the CMIP5 (Coupled Model Intercomparison Projectphase 5) experiments and the fifth assessment report of the IntergovernmentalPanel on Climate Change (IPCC-AR5). In this manuscript, we focus onevaluating the ocean and land carbon cycle components of the NorESM, based onthe preindustrial control and historical simulations. Many of the observedlarge scale ocean biogeochemical features are reproduced satisfactorily bythe NorESM. When compared to the climatological estimates from the WorldOcean Atlas (WOA), the model simulated temperature, salinity, oxygen, andphosphate distributions agree reasonably well in both the surface layer anddeep water structure. However, the model simulates a relatively strongoverturning circulation strength that leads to noticeable model-data bias,especially within the North Atlantic Deep Water (NADW). This strongoverturning circulation slightly distorts the structure of the biogeochemicaltracers at depth. Advancements in simulating the oceanic mixed layer depthwith respect to the previous generation model particularly improve thesurface tracer distribution as well as the upper ocean biogeochemicalprocesses, particularly in the Southern Ocean. Consequently, near-surfaceocean processes such as biological production and air–sea gas exchange, arein good agreement with climatological observations. The NorESM adopts the sameterrestrial model as the Community Earth System Model (CESM1). It reproducesthe general pattern of land-vegetation gross primary productivity (GPP) whencompared to the observationally based values derived from the FLUXNET networkof eddy covariance towers. While the model simulates well the vegetationcarbon pool, the soil carbon pool is smaller by a factor of three relative tothe observational based estimates. The simulated annual mean terrestrial GPPand total respiration are slightly larger than observed, but the differencebetween the global GPP and respiration is comparable. Model-data bias in GPPis mainly simulated in the tropics (overestimation) and in high latitudes(underestimation). Within the NorESM framework, both the ocean andterrestrial carbon cycle models simulate a steady increase in carbon uptakefrom the preindustrial period to the present-day. The land carbon uptake isnoticeably smaller than the observations, which is attributed to the strongnitrogen limitation formulated by the land model.
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