Breakout Session 6 -- Spatial and Temporal Scales
What are the spatial and temporal scales required to resolve questions concerning climate
change and carrying capacity?
Discussion Leaders: Robert Francis and Warren Wooster
Participants: Bud Antonelis, Ted Cooney, Michael Dahlberg, Art Kendall, Kate Myers, Charles
Miller, Phyllis Stabeno, Vidar Wespestad.
Presumably the spatial scale of climate forcing is large, basin scale at least, encompassing the
equatorial Pacific (as it relates to ENSO) as well as the system of highs and lows extending from
Siberia to the west coast of North America. Variations in the atmospheric pressure field are manifested
through variations in air/sea heat and momentum exchange, both of comparable large scale. The
surface layer of the ocean responds on similar and smaller scales, for example the mesoscale features
of eddies, convergences and divergences, etc. Vertically, the scale of surface layer thickness, of the
order of 100 meters, is particularly important.
Ecosystem scales appear to be smaller than those of climate forcing. However, if the climate forcing
manifests itself as Rossby waves or as poleward displacements of boundaries then they would be of
similar scale. The ecosystems of interest here are the Gulf of Alaska, the eastern Subarctic gyre, and
the eastern Bering Sea shelf. In considering the carrying capacity for salmonids in the Subarctic
Pacific, the dimension of the Subarctic gyres (i.e., the oceanic pasture) determine an important scale.
Even smaller systems can be defined, e.g., Puget Sound or Prince William Sound. These interact
with larger scales and may serve as microcosms for study of processes that typify the larger systems.
Process studies may encompass scales from that of the ecosystem to that of plankton patches or even
to the ambit of individual plankters.
While seasonal scales dominate life histories, longer time scales are more relevant in considering the
climate forcing of ecosystems. Much attention has been paid to interannual variability, but in the case
of climate fluctuations, decadal and longer scales seem to be more important and to have more
identifiable patterns. There has been particular interest in the regime shift scale, of the order of
decades. Note that, atmospheric changes may be more rapid than those in the ocean due to the greater
heat capacity of the ocean, and lags between forcing and response may differ from region to region.
Time scales of ecosystem response are less clear. Seasonal, interannual, and decadal scales are all
evident. Different trophic levels and key species have different response times and scales. Little is
known about the time scale of changes in carrying capacity for high level carnivores, which may be on
the regime shift scale or longer. High level carnivores like marine mammals and seabirds are long
lived species that must be able to withstand annual and decadal variations in food resources over large
spatial and temporal scales. During the breeding season birds and fur seals have a limited foraging
range since they must return to feed their young waiting onshore. Breeding sites are therefore limited
to islands or continental regions with a oceanographic regime that ensures an abundant and predictable
supply of food throughout the breeding season. Furthermore, since these animals are long lived and
show high degrees of site fidelity, resource availability must be reliable over time scales of many years
- There is a continuum of spatial and temporal scales of concern to the program. Criteria for
selecting specific scales are: (1) those where important variability is concentrated, (2) those that relate
to plausible mechanisms of interaction, and (3) those that relate to applied problems.
historical data, such as CalCOFI, Ocean Station P, GAK1, FOCI line 8 and PROBES lines, are
extremely valuable time series and should be considered by those contemplating new sampling
- The comparison of events in different regions and at different times is a powerful approach
which can be facilitated by PICES. Comparisons between the eastern and western Bering Sea and
Subarctic Pacific are likely to be particularly fruitful. An important PICES contribution can be to make
data from the western Subarctic Pacific more accessible.
- From an ecosystem point of view, there are species (or groups) that have been consistently
missing in ecosystem analyses. These include forage fish species, jellyfish, and top carnivores such
as marine mammals, seabirds and humans (which are a major component of top-down forcing).
- Relatively short time scales are amenable to direct study whereas decadal and longer scales
can only be studied through retrospection and modeling.
- An important question is how different species respond to climatic forcing at different