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Notes on “Model-derived estimates of new production: New results point towards lower values” by Oschlies (2001)

“A compilation of published model results further suggests that variations among the presently available model-derived estimates of new production depend primarily on the architecture of the physical model chosen, and mainly reflect systematic differences in diapycnal mixing. Different ecosystem model configurations, on the other hand, turn out to have relatively little effect on the simulated large-scale new production, while they determine the level of regenerated and hence total primary production.

To convert carbon to nitrogen estimates in this paper, a constant Redfield ratio of 6.625 molC / mol N is used. Additionally, it will be assumed that on a basin-scale and annual average, export production equals new production and that nitrogen fixation can be neglected. Any net effects of nitrogen supply via riverine or atmospheric inputs and of deposition in the sediments are neglected in this study.”

They describe (p. 2180-2181) the method used to compute new primary production. The method was chosen in order to enable comparison with previous model studies, not necessarily with observations.

Effect of advective scheme:

“Averaged over the entire north and equatorial Atlantic, the unrealistically large dillusion implicit in the upstream scheme leads to an increase of the nitrate supply from 0.3 mol N / m2 / yr in the STANDARD experiment using MPDCD advection to more than 0.5 mol N / m2 / yr when UPSTREAM advection is used (Fig. 1).”

The rest of the paper talks about issues concerning numerics but does not actually compute and compare horizontal and vertical advection for specific region.