Processes in European and Global Seas
(^) Model ocean ecosystems are also expanded to two and three spatial dimensions, at the
expense of more computing. Typical two-dimensional models represent explanations
of onshore–offshore, surface-to-seafloor patterns of production and grazer
distributions in coastal areas such as the upwelling zones (e.g. Edwards et al. 2000).
In three-dimensional models, patterns and cycles are constructed for spatially variable
ocean sectors and for the entire world ocean (Zahariev et al. 2008, and many more).
(^) Pelagic ecosystem simulations are frequently taken to extremes, attempting to
include virtually every significantly distinctive component known to be part of the
system. The ERSEM-PELAGOS model is an example. It has 44 state variables (Fig.
4.11), more than appear in the diagram because C, N, P, and in some cases Si and Fe,
are independently tracked within living or detrital components. There are about 300
parameters (the authors did not count them for us). Because many of the parameters
are tuned to make the model match data, the model appears to generate reasonably
realistic profiles, seasonal cycling (Fig. 4.12) and maps (see Vichi et al. 2007a & b).
However, while the patterns appear realistic, actual quantities are often off by two-
fold. For some purposes it may not matter whether the incorporated processes and
exchanges are close representations of real ocean physics and ecology, if the output
patterns fit the maps and cycles. On the other hand, if the mechanics are just a fit
forced in some way, then a model will not correctly predict effects of changed
environmental forcing (climate change, overfishing, eutrophication, ...). To an
increasing extent, human activity constitutes management of the oceans’ ecology, as it
does of all Earth habitats. Wisdom in that management depends increasingly on these
complex models. If their mechanics are not realistic, then they will provide
misleading predictions and misleading advice for the design of our interactions with
nature.
Fig. 4.11 Box diagram for the PELAGOS version of ERSEM (European Regional
Seas Ecosystem Model).
(^) (After Vichi et al. 2007a.)