Phosphorus model worksheet answers
The article provides answers to the questions posed in the phosphorus model worksheet.
- The model will (should!) converge in all cases, for absolutely any initial conditions.
- Yes, final steady state should always be the same (if run for long enough – there may be minor differences because equilibrium hasn’t quite been reached).
- Yes, burial flux is larger after doubling deep PO4, smaller after halving it.
- Increase of deep phosphate concentration has a greater impact. This is because the deep box has a greater depth and therefore a greater volume. Increasing the deep box concentration by 1 mmol m-3 therefore adds more P to the system as a whole.
- More PO4 → more PO4 in upwelled/mixed up water → more phytoplankton → more export → more burial → increased rate of loss of P from the system → PO4 levels come back down again.
- Doubling RP doubles surface box phytoplankton concentration and TPP. Halving RP halves them both.
- Steady-state surface phosphate is identical in the two runs. The important point here is that it is nutrient supply not instantaneous nutrient concentration that controls productivity. This has been an important misconception in the past.
- Doubling K does produce a long slow decline in deep phosphate concentration. The timescales are different. In this model half of the change is achieved in about 9300 years, rather quicker than estimated by Broecker & Peng.
- Phosphorus model overview
- Phosphorus model details
- Phosphorus model pros
- Phosphorus model cons
- Phosphorus model help
- Broecker, W.S. & Peng, T.H. (1982) Tracers in the Sea, Eldigio Press, pp. 275-284.