NWA-Chapter 3-Intro

## Chapter 3 -- Introduction

The primary objective of the GLOBal ocean ECosystem dynamics program is to understand the underlying physical and biological processes that control the abundance of key populations of marine animals in space and time (Peterson and Powell, 1991). The ultimate application of this knowledge is to understand the marine ecosystem as it relates to marine living resources and to understand how fluctuations in these resources are driven by climate change and exploitation (GLOBEC, 1991b). It is assumed that changes in the recruitment of fish and zooplankton are rooted in the early stages of life. Thus, we can understand the links between recruitment and climatic change only if the population parameters in those early stages are described and understood. To begin this long-term program, the initial U.S. GLOBEC effort focuses on understanding and quantifying of present day physical forcings and their effects on the population dynamics of selected target species.

The first intensive U.S. GLOBEC field study will be conducted in the Georges Bank region of the Northwest Atlantic starting in 1994 (GLOBEC, 1991c; Figure 1). This area was chosen because: Georges Bank is of sufficient size and has a physical circulation which enables distinct trackable populations to develop and persist for long periods amenable for time-series study; Georges Bank supports a very productive fisheries and is thought to be highly sensitive to climatic change because it is positioned in a faunal and physical boundary region; and Georges Bank is in a region predicted to be more heavily impacted by climate change than other areas in the North Atlantic Ocean (Manabe et al., 1991). Target taxa to be studied include pelagic life stages of cod and haddock and their major prey and predator species. The overall goal of the Georges Bank Study is to determine how biological and physical processes interact to control abundance of these target species populations on Georges Bank in space and time. This information then can be used to assess the potential fate of these populations under various plausible global climate change scenarios.

This report presents a conceptual plan for the implementation of the U.S. GLOBEC Northwest Atlantic/Georges Bank Study. The report begins in Section 4 with a brief review of the Georges Bank ecosystem, giving the specific characteristics of this region which make it suitable for intensive study. Then the physical oceanography of the Bank and the target species are described. Section 4 ends with a discussion of the key physical/biological interactions occuring on the Bank and the main scientific hypotheses of the study. The main components of the study are then presented in Section 5. These include an experimental program of both broad-scale and smaller-scale process studies, methodology and instrument development, modeling, and historical data analysis. Requirements for program management and data management are discussed in Section 6, and the relationships between this study and other national and international programs are described in Section 7.

The framers of this report hope that the proposed implementation plan represents a valid attempt to craft a sound scientific program, and that further planning by the larger scientific community will find this initial plan a useful starting point. It should be obvious that the magnitude of the program will be driven by availability of funding. Despite the realization that not all of the scientific issues discussed here can be (or ever will be) funded, we felt that it was better to outline an ambitious program than a more limited one which lacked vision. When initiated, the Georges Bank study will be a complete program in the sense that it will address physical-biological objectives which are judged to have the greatest relevance to the issue of climate change. The challenge to all prospective investigators is to demonstrate convincingly that their work leads to a new level of understanding of the links between the atmosphere, ocean physics, and population dynamics of marine organisms, in the context of climate change.

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