The Key Scientific Questions postulated in the Science Plan have since been consolidated into the following set of so-called Central Scientific Issues:
Key research activities related to these issues will include retrospective analyses, development of models, process studies, development of observational systems, and data management. The next steps in developing the CCCC implementation plan on the regional scale are expected to include efforts to design the proposed comparison of ecosystem properties and responses to climate variability in cooperation with national GLOBEC programs. On the basin scale, a more comprehensive effort to develop an international cooperative program will be required.
The North Pacific is the location of one of the major storm tracks in the northern hemisphere. Models suggest that the southern side of the Arctic front will be the region of greatest alteration due to global climate change. The storm track responds to two global teleconnections patterns, the West Pacific oscillation that influences the location of storm generation and the Pacific-North American pattern that influences the track of storms across the subarctic Pacific. The Pacific-North American pattern is often considered the major mode of planetary variability of the atmosphere. We can hypothesize the shift in storm frequency and track due to climate change and its potential impact on the physical environment. At present, considerable natural variability exists on time scales from seasonal to decadal. This variability has a profound impact on circulation, mixed layer depths and the extent of ice coverage, all of which influence the rich biological resources of the subarctic Pacific.
U.S. GLOBEC and PICES are now poised to take advantage of newly developed tools that will enable us to examine the carrying capacity of the subarctic Pacific. These include measurement technologies and complex computer models. The vast time-space scope of the environmental questions requires application of technologies such as remote sensing via aircraft and satellite, shipboard data acquisition systems such as those employing acoustic sampling of currents and biota, and moored platforms to collect time series of biological and physical observations. Advances in computer technology now permit using large-scale models that assimilate field observations and integrate biological and physical processes.
A U.S. GLOBEC program in the North Pacific would benefit from parallel development of complementary research programs of other nations through the PICES-GLOBEC CCCC program. International cooperation on a common research program will inevitably enhance our national research efforts. In the case of coastal programs, Japanese and Russian studies in the Bering Sea, and Canadian research off British Columbia will augment U.S. investigations of ecosystem responses to climate variability.
U.S. GLOBEC research in the North Pacific would complement proposed research on the influence of climate variability on marine ecosystems in the California Current (U.S. GLOBEC Report 11). Coordination with the California Current program is highly desirable because large scale forcing for both regions could be modeled simultaneously, and because of earlier suggestions that the physical and biological systems of the two regions-California Current and Alaskan GyreÑoperate oppositely in phase (Chelton and Davis, 1982).
Canadian scientists also have a long history of fisheries oceanographic research in the Pacific. The Canadian La Perouse program provides a continuous time series of biological and physical oceanographic conditions off the outer coast of Vancouver Island since 1985.
The FOCI and the Canadian La Perouse programs are among the most mature fisheries oceanography programs in the world. Very few fisheries oceanography programs have been able to maintain continuous coordinated research for more than a decade. The results from these two programs provide many of the critical parameters for the development of the larger scale ecosystem models necessary to study climate change and carrying capacity. For example, the FOCI program has enumerated abundance trends at various life stages of early development; examined processes affecting life stages; mapped horizontal, vertical, and temporal distributions; described the oceanic and atmospheric environment; developed coupled bio-physical models of the Gulf of Alaska, and developed techniques to examine recruitment-process hypotheses.
The open sub-Arctic region will include Pacific waters north of the position of the isohaline of 34.0 psu in the upper mixed layer, with the exception of the coastal regions over the continental shelf and slope (to depths of 1000 m).
Coastal regions of the subarctic Pacific will include all waters over the continental shelf and slope to depths of 1000 m. This region will include areas south of the Aleutian Islands to the western boundary of U.S. waters at 173 E.
Some species, such as salmon, undertake seasonal migrations that cross both the coastal Gulf of Alaska and the open subarctic. In such situations, it may be necessary to include processes from adjacent regions (such as the coastal Gulf of Alaska or Bering Sea), if they significantly affect the physics, chemistry or biology of the subarctic gyre.
Breakout Session 1. Climate Change: What are the likely scenarios for climate change in the North Pacific and how would they influence the ecosystem?
This group discussed the potential impact of climate change caused by increased CO2 and other greenhouse gases from anthropogenic sources. Climate change would influence North Pacific ecosystems primarily through four physical factors: mixed layer depth (MLD), volume and location of marine habitat, sea ice, and river flows. Time variation in late spring/summer MLD is the physical oceanographic measurement which may correlate most highly with primary and secondary productivity in the coastal Gulf of Alaska and Bering Sea shelf. Changes in marine habitat, thus the zoogeographic distribution of marine species, are expected to accompany ocean warming, with particular impacts on species at the edge of their ranges. Sea ice is foreseen to decrease both in space and seasonal duration, with effects on the Bering Sea's primary productivity and distribution of many marine mammals. The overall magnitude and seasonal cycle of river flows may change significantly, with implications for coastal currents and freshwater habitats for salmon.
Breakout Session 2. Regime shifts: Can they be detected, what is their impact, are they predictable?
Long term variations in ocean conditions appear to occur at two different time scales and the biological responses appear to differ in magnitude. The temporal periods most commonly mentioned are: 1) decadal and bi-decadal scale shifts, including 6-12 year warm and cool eras and the 18.6 year cyclic phenomenon (Trenberth and Hurrell 1994; Hollowed and Wooster 1992; Royer 1993), and 2) regime shifts that are 30-60 year cycles and appear to generate measurable ecosystem responses (Francis and Hare 1994; Baumgartner et al. 1992; Kawasaki 1992). There is compelling evidence of interdecadal changes in the physical environment of the North Pacific and Bering Sea. The most recent regime shift occurred in the late 1970s. The changes appear to be linked to large scale shifts in atmospheric processes. Marine organisms seem to respond to these decadal scale changes in the physical environment. The group acknowledged that research is required to improve our understanding of the mechanisms underlying the response of marine organisms to shifts in physical conditions. North Pacific basin modeling shows promise in simulating and explaining decadal fluctuations of the ocean over coarse scales. Regional and mesoscale oceanographic models exist for the Gulf of Alaska and need to be developed for other regions. Several physical and biological variables were identified that could be used as diagnostic indicators of regime shifts.
Breakout Session 3: What is carrying capacity?
This group discussed the concept of carrying capacity and methods of measuring it. The group adopted the following definition of carrying capacity: "Carrying capacity is a measure of the biomass of a population that can be supported by the ecosystem. The carrying capacity changes over time with the abundance of predators and resources (food and habitat). Resources are a function of the productivity of the prey populations and competition. Changes in the biotic environment affect the distributions and productivity of all populations involved." Rather than measuring carrying capacity as an absolute value, or providing a rigorous definition, the group discussed indices of carrying capacity that could be used to assess relative changes in the status of a population. The group noted that size spectrum theory, which relates rates of productivity to the size class of organisms in the ecosystem, is a potentially valuable conceptual framework for examining carrying capacity questions.
Breakout Session 4: What is required to model the impact of climate change on the carrying capacity of the region?
Participants discussed a variety of modeling approaches and suggested that different types of models be nested spatially, temporally and trophically. Physical models of the North Pacific and Bering Sea already exist and could be utilized in the U.S. GLOBEC program. While the formulation of governing equations and choice of parameters for biophysical models is difficult, reasonable choices can be made. Encouraging results have been obtained from the application of coupled biophysical models in other areas of the world (such as the North Atlantic).
Breakout Session 5: What are the technological impediments to measuring the effects of climate change on the carrying capacity?
Climate change by definition is a large scale, long term process (decadal) and will require ample measurements collected over a large geographical area for a long duration. A successful program will require careful selection of study sites at key or pulse points where the variance is minimized and the effects of climate change on carrying capacity are indicative of large scale change. A variety of technological issues were discussed and the disadvantages and advantages of each were identified. The group encouraged efforts to measure sea-surface salinity from satellites to map the large-scale distribution of this variable which can be dynamically more important than temperature in the Gulf of Alaska and Bering Sea. They also noted that deep ocean currents could be monitored using electro-magnetic observations from submarine telephone cables and identified the Kamchatka Current and Alaskan Stream as possible pulse points. Finally they noted the need for research on non-commercial species such as jellyfish or forage fish. These species may play a critical role in determining the carrying capacity of oceanic systems, and at least in the case of the "jellies" require specialized sampling.
Breakout Session 6: What are the spatial and temporal scales required to resolve questions concerning climate change and the carrying capacity?
This group concluded that the spatial scale of climate forcing is large-basin scale at least. The group noted that while considerable attention has been devoted to interannual variations, decadal and longer time scales may be more important for resolving issues of climate forcing and its impact on marine ecosystems. Participants acknowledged that the response time to climate change differs among species, which complicates the interpretation of biological/ecological systems to climatically driven physical changes. Criteria for selecting specific time and space scales for a future U.S. GLOBEC study must include: 1) important sources of variability must be concentrated, 2) relationship to plausible mechanisms of interaction, and 3) related to applied problems.
In the Gulf of Alaska, bio-physical models have been developed for British Columbia, Prince William Sound and Shelikof Strait. Efforts to nest regional models into a large-scale biophysical model of the Gulf of Alaska were recommended. A broad-scale biological model of the Gulf might include the following: phytoplankton, protozoa, euphausiids, copepods, jellyfish salmon, herring, and pollock.
Chelton, D. B., and R. E. Davis. 1982. Monthly mean sea-level variability along the west coast of North America. J. Phys. Ocean., 12, 757-784.
Francis, R. C. and S. R. Hare. 1994. Decadal-scale regime shifts in the large marine ecosystems of the North-east Pacific: a case for historical science. Fish. Oceanogr., 3, 279-291.
Hollowed, A. B. and W. S. Wooster. 1992. Variability of winter ocean conditions and strong year classes of Northeast Pacific groundfish. ICES mar. Sci. Symp., 195, 433-444.
Kawasaki, T. 1992. Mechanisms governing fluctuations in pelagic fish populations. So. Afr. J. Mar. Sci., 12, 873-879.
Royer, T.C. 1993. High latitude oceanic variability associated with the 18.6 year nodal tide. J. Geophys. Res., 198, 4639-4644.
Trenberth, K. E. and J. W. Hurrell. 1994. Decadal atmosphere-ocean variations in the Pacific. Climate Dynamics, 9, 303-319.
