Modeling has been a central element of U.S. GLOBEC programs for a variety of reasons. Foremost,
is the fact that by its very nature, the fundamental goal of U.S. GLOBEC--to predict the effects of
future climate change--requires a predictive model. Models are the means of understanding complex
interactions and projecting this understanding into the future for use in, for example, fisheries
recruitment prediction. The Northeast Pacific program will generate information and understanding
from a variety of disciplines (e.g., biology, physical oceanography, atmospheric sciences), a range of
temporal and spatial scales, and several levels of biological organization (i.e, individual bioenergetics,
population dynamics, food web interactions). Models will be required to integrate these so that the
information can be used to project the consequences of likely climate change. To do this, we need
models that span the range from the scale of basin-wide and decadal changes such as regime shifts to
the scale of individual diel planktonic movement over meters. Modeling studies will be closely
coordinated with monitoring, retrospective analysis and process studies. Building on the experience
on Georges Bank, the large-scale modeling will be one of the first activities of the program. This early
start is important to capture climate scale variability, set the boundary conditions for regional-scale
models and the process studies, and recommend representative monitoring tactics.
In addition, models in this program will function as essential elements of the scientific efforts. Here
too, they will serve to integrate various types of information, but the goals will be different. They will
be used to test hypotheses, to determine sensitivities, to plan research, and to evaluate the results of
To meet the general goals of the U.S. GLOBEC Northeast Pacific program, the models can focus on
the broadest suite of species and issues relevant to the effects of climate change on North Pacific
coastal ecosystems. Modeling studies may be developed with a focus on species targeted for the
process studies (Table 3) or other non-targeted species, which could be sampled in the monitoring or
analyzed in retrospective studies (Table 4).
Development of models well in advance of any field investigations has been an explicit goal of the
U.S. GLOBEC program. An earlier U.S. GLOBEC workshop on secondary production modeling
identified five general issues which are critical to predictive modeling that couples physical and
biological processes (U.S. GLOBEC 1995).
Planning activities for the Northeast Pacific program (U.S. GLOBEC Report No. 11, 1994; and U.S.
GLOBEC Report No. 15, 1996) have identified four specific modeling efforts that are needed to address these general issues.
- The role of organism motility (independent of the fluid medium), especially for the higher trophic
level populations on which GLOBEC focuses. Several of the target organisms are more than passive
floaters--they make choices such as vertical migration, swarming, etc.--and this has implications for
transport, retention in favorable habitats, growth and survival.
- Differences in trophic organization--for example, food webs with gelatinous zooplankton as
top predators, compared to those with carnivores, like salmon, at the highest trophic level.
- The coupling of processes acting at different spatial and temporal scales, as well as different
levels of organization. An ultimate goal is the development of large- or basin-scale models that are
coupled to more-detailed regional-scale biophysical models, and are capable of forecasting effects of
climate changes on the zooplankton and fish populations.
- The incorporation of data into models, and the converse activity of utilizing model results to
plan and to interpret field and laboratory studies.
- The availability of coupled biological-physical models to the larger community, and a
broad-based community modeling effort with an enduring funding commitment.
Several necessary lines of investigation cut across these model types. For example, the functional
details of how to parameterize individual interactions between organisms (e.g., predator-prey) is a
challenge to modelers at all scales. Moreover, how one might embed a regional model of coupled
biological-physical processes within a basin-scale circulation model, or a mesoscale formulation within
a regional model, remains a challenge. Technical concerns, like the specification of boundary
conditions, particularly along open boundary segments, are far from settled at any scale. The
assimilation of biological data into models of all kinds is another unsolved (and barely addressed)
problem. Finally, models need to be verified, for it is only verified models that are of ultimate use.
- Basin-scale general circulation modeling with higher-resolution, nested coastal
biological-physical components. A link to entire North Pacific simulations that are coupled to large
scale atmospheric models would be desirable, especially for hindcasting studies.
- Regional-scale coupled biological-physical models. The best of these endeavors would aim
to assimilate available observations (e.g., remote sensing data, buoy data, etc.), resolving the
exchange of water and organisms between the coastal shelf and deeper oceanic waters.
- Coupled (mesoscale) biological-physical formulations. Models of this type should aim to
resolve fronts, include mixed-layer dynamics, possibly address the shallow, turbulent inner shelf, and
operate over diurnal time scales. They might address the separation of the upwelling front from the
coast, including the relative roles of topographic irregularities and wind forcing. They should
incorporate coastal transport processes and detailed biology, including food web relations and
- Modeling efforts that investigate the response of biological metapopulations to spatially and
temporally varying physical forcing (Botsford et al. 1994). Some attention should be paid to models
with very detailed biology, and less detailed physical transport. Examples might include bioenergetic
models of juvenile salmon, predator relations, seasonal prey switching behavior, and/or nearshore
food web dynamics for several different environmental scenarios. Some of these issues might best be
addressed by individual-based models.
A significant constraint on future progress is the lack of reliable and generally accepted coupled models
available to the research community at large. Few users can be found even for those models for which
some level of reliability can be claimed. To remedy this situation will demand resources for community
model development and testing, and a commitment to the user communities. Rapid response to these
widely acknowledged needs would allow the broader community to take advantage of opportunities
represented by recent improvements in computer architectures, high-speed networking capabilities,
and hierarchical data management and retrieval systems.