Questions and Goals

# SECTION V-CENTRAL QUESTIONS AND GOALS

The goal of U.S. GLOBEC is to understand the linkages between climate variability and long-term change, and the distribution and abundance of animal populations, including many that are important to society. The CCS offers an excellent opportunity to accomplish this goal. In the CCS we can exploit known spatial and temporal variations in physical processes and biological responses to project population trajectories under different scenarios of climate change. We can utilize: 1) the present latitudinal variations within the CCS; 2) interannual (periods of 2-10 years) temporal variability within the CCS, especially as linked ENSO cycles; 3) the extensive historical data sets within the CCS, which can be used to identify natural modes of variability; and, 4) present day differences between the CCS and other EBCs, to examine ecosystem responses to differences in the strengths of local and basin-scale forcing.

The central, over-riding question that drives the proposed U.S. GLOBEC study of the California Current System is:

How will the distribution, abundance, and life history characteristics of marine animal populations respond to climatically driven changes in the CCS?

## More Specific Questions

The central question can be expressed as a series of more specific questions that reflect the broad range of spatial and temporal scales in which physical-biological couplings in the CCS are manifested. Within each category we pose, as examples, several even more specific questions. It should be noted that these questions are not meant to be exhaustive, but rather to provide the reader with guidelines for the types of questions that might be investigated during a program examining the impact of climate change on EBC ecosystems.

- Interannual Variability in Biological Responses

- Interdecadal Variability in Biological Responses

- Mesoscale Variability in Biological Responses

- Latitudinal Gradients in Biological Responses

## Approach to Answering the Questions

Questions regarding the impact of climate change on the CCS ecosystem are best addressed using a combination of modeling, field work, monitoring and retrospective data analysis. Our recommended approach to answering the questions is to identify and understand the most important links, at present and in the historical record, between the physical processes of the CCS and key population and ecosystem properties. Subsequently, this understanding will be applied to predict the responses of these populations to climate change. Identification of the most important biological-physical couplings is essential to both modeling and field efforts, since it is impossible to include every detail of an ecosystem in any tractable study.

The foundation of this approach will be the study of spatial and temporal variability in biological processes of the CCS, relative to physical processes of the CCS that might control biological variability. To help identify the physical processes to which population dynamics in the CCS are most sensitive, we recommend several initial activities (modeling, retrospective and comparative studies) in advance of new field studies. To aid future field studies, initial activities should also include technology development. These activities are discussed briefly in Section II, and in more detail in Section VII. New field studies will then be directed toward understanding the dominant processes responsible for present-day and historical distributions and abundances of populations (and their genetic composition), patterns of transport and recruitment of critical life stages of both fish and benthic species, and trophodynamics. Once the relevant processes are identified and their mechanisms are better understood, they can then be incorporated into quantitative, descriptive biological-physical models. The accuracy of these models can be evaluated in part by their abilities to hindcast historical time series and also predict present-day spatial variability. We expect this research to lead to a new generation of prognostic biophysical models, which will continue to be improved as they are used operationally and in research activities. They should be available for use with the next generation of coupled ocean-atmosphere GCMs, which will have higher resolution and provide boundary conditions for the prognostic ecosystem models. The ultimate goal is to understand the relevant processes and linkages enough to develop operational, prognostic biophysical ecosystem models that, when coupled with GCMs, can be used to assess (and predict) the impact of potential climate change on the status of living marine resources within the CCS.