Modelling the nitrogen cycle and DMS production in Lagrangian experiments in the North Atlantic

A 0-dimensional model of the ocean ecosystem, which includes the nitrogen and sulphur cycles, is compared with two existing Lagrangian data sets from the North Atlantic: BOFS (1990) and PRIME (1996). The model contains rate parameters, which are optimised to obtain best fits to the data. It is found that published values of the rate parameters are incapable of fitting the data. However, good fits can be obtained with parameters reasonably close to the published values, many within a factor of 1.5 and almost all within a factor of 2.0. In the case of the PRIME data, the modelling was done in two ways: with and without optimising to the DMS production. The best-fit rate parameters in the latter case predicted a DMS production rate too low by a factor of 30. In the former case the DMS production was predicted well with a relatively small effect on the modelʹs prediction of the other variables. However, this best fit changed a number of the rate parameters both for sulphur and nitrogen cycle. This implies that while feedback between the sulphur and nitrogen components of the plankton community is small a good description of the sulphur cycle also can provide information about rate parameters within the nitrogen cycle.