Regional Ecosystem Model Testbeds: A JGOFS Synthesis and Modeling Project

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An important legacy of the U.S. Joint Global Flux Study (JGOFS) Synthesis and Modeling Project (SMP) will be the formulation of a broad suite of models designed to simulate biogeochemical cycling at the various process study sites. Although this set of models and modeling studies has already substantially advanced our understanding of these systems, few quantitative inter-comparisons of these models have been made. This project will begin to conduct these inter-comparisons, in order to critically examine which ecosystem structures and formulations are most robust, and to investigate and explore the reasons for their success. Furthermore, it will critically evaluate the feasibility of developing biogeochemical models that are applicable over a wide range of diverse ecosystems. The main objectives of the proposed work are: (1) to add to the mechanistic understanding of how and why euphotic zone production, and the associated export of carbon, vary among diverse oceanographic regions, and (2) to accelerate the development of mechanistically-based ecosystem models that are capable of simultaneously describing the primary biogeochemical features of multiple oceanographic regimes. In order to accomplish these goals, and to provide a forum for testing and comparing various ecosystem models, the investigators will develop a series of "regional test-beds," based on the high quality and large quantity of observations available from (i) the Arabian Sea Process Study (ASPS), (ii) the Antarctic Environment and Southern Ocean Process Study (AESOPS), (iii) the Equatorial Pacific Process Study (EqPac), (iv) the second iron enrichment experiment (IronEx-II), (v) the Bermuda Atlantic Time-Series Study (BATS), and (vi) the Hawaii Ocean Time-series (HOT). Websites will be constructed for all test-beds and will include access to the physical fields required to force the models, as well as time-series of biogeochemical data that will be used for either evaluation or optimization/assimilation. These websites will be available as a community resource, and, in this study, will be used to facilitate both intra-site and inter-site model comparisons. This research will capitalize on work previously accomplished under the JGOFS SMP: the twelve co-investigators involved in this project (see letters of collaboration) will freely provide their regional expertise, model code, forcing fields, and biogeochemical data sets to this project. To further promote model inter-comparisons, this project will involve annual hands-on workshops in which scientists (including but not limited to the co-investigators of this proposal) will work together to quantitatively assess a number of different biogeochemical models and modeling approaches. Through these inter-comparison exercises and carefully designed simulations, the improvement of biogeochemical models will be accelerated, and the scientific community will be significantly closer to having a set of rigorously tested models that can be used for ocean carbon cycle prediction.