HIERARCHAL INDUCTIVE PROCESS MODELING AND ANALYSIS ...

specifying the space of possible equations and a dependent variable and will output
the best equation for the variable, able to only perform the search for one variable
at the time (Dzeroski et al. 1993, Todrovski 2003). This is further related to the
methods used in Ljungs work (1993) on system identification, but is further removed
to that of inductive process modeling.
The main assumption behind system identification is that the model structure
is known and that the primary concern is finding the adequate parameter values;
equation discovery focuses on both the structure and parameter values (Todorovski
et al. 1998). Both of these approach produce descriptive models that summarize
and predict the data but they fail to search through the space of alternative explanations,
these methods do not take into account models with theoretical variables
or consider alternate processes to explain certain dynamics (Bridewell et al. 2005).
The Southern Ocean covers an area equivalent to about 10% of the global ocean
and is a key element of the global ocean system as it links all major ocean basins and
facilitates the global distribution of its deep water; it is considered to play an important
part in the global carbon (C) cycle (Arrigo et al. 2003). The Ross Sea polynya
(area of open water surrounded by sea ice) is one of the most productive ecosystems
in the Southern Ocean as it experiences some of the largest phytoplankton blooms
in the region (Arrigo et al 1994, 1998, 2000, 2003). Indeed, phytoplankton productivity
(photosynthesis) is important to the carbon cycle as it removes carbon dioxide
(CO 2 ) from surface water during photosynthesis, part of which will then be exported
to deep ocean water. What makes the Ross Sea polynya so interesting for ecologist
compared to other locations such as Terra Nova Bay, is the type of phytoplankton
dominating the ecosystem. In the Ross Sea polynya , Phaeocystis antartica dominates
as opposed to diatoms (species such as Fragilariopsis spp.) in Terra Nova Bay.
Phaeocystis antartica are thought to resist grazing more than other phytoplankton
species, which could imply that more carbon would be taken from shallow water into
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