Modelling the seasonal course of the upper ocean pCO₂ (II). Validation of the model and sensitivity studies

A one-dimensional model was developed, aiming at the simulation of the seasonal course of the upper-ocean pCO₂. This model is validated here, by comparing its outputs with field data, at the Ocean Weathership Station Papa in the Northeast Pacific Ocean (from 1975 to 1977). This simulation emphazises the leading role of biology in changing the inorganic carbon content at this station, compared to those of eddy diffusivity, entrainment and air-sea exchange. Complex and intricated dependences of pCO₂ variations on temperature, μCO₂ and TA are analysed. On the occasion of a comparison of the model with that of Taylor et al. the pitfalls of univocal correlations between the sea-surface pCO₂, temperature and Chl at a given site are put in evidence on the basis of their complex and divergent annual evolutions. Sensitivity tests quantitatively show the importance for the model of (i) the representation of the chlorophyll cycle (ii) the mean value selected for the f-ratio. Some possible developments of the model, and its applications in view of assimilating remotely-sensed data are discussed.