Description of the Nitrogen and Phosphorus Model.
This model is very simple. It is stripped down to the simplest form that can still reproduce the nitrogen (N) and phosphorus (P) cycles. That is to say, the simplest form that can capture the main aspects of how atoms of nitrogen and phosphorus enter the ocean, are transported about within it, and then finally leave the ocean. The aim of this model is to understand how the nitrate:phosphate ratio of the ocean is regulated, and also how the amount of plants in the ocean, and therefore the fertility of the ocean as a whole, are controlled.
The diagram above shows how the oceanic cycles of nitrogen and phosphorus are represented in the model. As well as including the same cycling of phosphorus as in the phosphorus-only model, the model also represents how atoms of nitrogen enter and leave different substances (for instance, bodies of living organisms or molecules of dinitrogen and nitrate) during their time in the oceans.
The model is a two-box model of the global ocean. Or, in other words, the model consists of two boxes, one on top of the other. The top box represents the surface ocean down to the limit of the deepest wind-induced mixing during the year and the bottom box represents the deep ocean below the influence of wind and waves.