Table of Contents

• Dataset Description
• Parameters
• Deployments
• Project Information
• Program Information
• Funding

A major achievement of the last decade of oceanic observations by the Joint Global Ocean Flux Study (JGOFS) and World Ocean Circulation Experiment (WOCE) has been the dramatic improvement in our ability to use observations to estimate the oceanic inventory of anthropogenic carbon. This improvement has been driven both by increased data and by the development of improved techniques for analyzing the observations. An important role has been played by the rapid development of ocean general circulation models that are now being used routinely to do tracer simulations and provide estimates of anthropogenic carbon uptake. However, despite the great progress that has been made, there remain many important issues that need to be resolved. The Ocean Carbon Model Intercomparison Project (OCMIP) shows very large differences between model simulations, particularly in the deep ocean tracer distributions, in the long term behavior of the models with respect to uptake of anthropogenic carbon, and in tracer-tracer relationships. Furthermore, there are very large disagreements with observations, particularly in the deep ocean. Some of the data analysis methods are based on assumptions that are difficult to verify and whose uncertainty is hard to estimate.

We propose to carry out model sensitivity studies to examine several hypotheses for model differences. We further propose to make use of measurements from the JGOFS and WOCE surveys to determine which model gives a more realistic simulation, and to improve our estimates of the oceanic uptake and storage of anthropogenic CO2, bomb radiocarbon, and CFCs. Our goal is to advance both the development of reliable ocean models and the estimation of oceanic uptake of anthropogenic CO2 from observations with the aim of improving estimates of the oceanic carbon sink and our understanding of the ocean carbon cycle.
First, we will examine model simulated tracer-tracer relationships of anthropogenic CO2, bomb ¹⁴C, and CFCs to evaluate four specific aspects of model physics that we believe are important in determining tracer distributions. They are;

1. the relative magnitude of advective return flows of the North Atlantic Deep Water through the thermocline and the Southern Ocean;
2. the magnitude of convective exchange between surface and deep waters in the Southern Ocean;
3. bottom boundary layer advective pathways of newly formed deep waters; and
4. the magnitude and spatial distribution air-sea gas exchange.

We will use the Princeton biogeochemical model to conduct a suite of simulations that isolate these mechanisms. Furthermore, model simulations will be compared with appropriate data from the JGOFS and WOCE surveys.

Second, we will improve the estimates of anthropogenic CO2 inventories by making use of the model simulations in conjunction with observations to critically examine the C* methodology of separating the anthropogenic CO2 from the background total CO2 [Gruber et al., 1996] and by exploring alternative methods using the distributions of CFCs, bomb ¹⁴C, and CCl4. The potential to use these measurements to estimate anthropogenic CO2 inventory rests on theoretical arguments and supporting preliminary observations that these transient tracers would be good analogs of anthropogenic CO2 distributions in the ocean, given the similarities in their growth history of CFCs and CCl4 in the atmosphere and the time scale since the injection of bomb ¹⁴C into the ocean. The robustness of the relationship of anthropogenic CO2 with CFCs, bomb ¹⁴C, and CCl4 will be investigated using our new simulations in conjunction with simulations from the OCMIP. We will then use the survey tracer data to improve estimates of the oceanic uptake of anthropogenic carbon.

We have gathered a team that has expertise in ocean observations and ocean biogeochemical modeling. A coordinated examination of these tracers that historically have been examined in relative isolation promises a better understanding anthropogenic CO2, bomb ¹⁴C, CFCs, and CCl4 uptake in ocean models and in the real ocean.

There were no cruises associated directly with the US JGOFS SMP. The SMP deployment refers to the project being deployed.

INTRODUCTION

The Joint Global Ocean Flux Study (JGOFS) was an international scientific program devoted to the study of the ocean biogeochemistry of carbon and related elements and the linkages of the ocean with the global carbon cycle. The U.S. JGOFS program involved a decade long, intensive field effort that included: two on-going time-series stations off Hawaii and Bermuda; a series of process studies in the North Atlantic, Equatorial Pacific, Arabian Sea, and Southern Ocean; and a Global Ocean CO₂ Survey in conjunction with the World Ocean Circulation Experiment (WOCE). The resulting ocean biogeochemical data sets, together with satellite ocean color data from the NASA Sea-viewing Wide Field-of-view Sensor (SeaWiFS), formed a unique, long-term resource for the ocean community. With the completion of the field phase in the late 1990s, the U.S. JGOFS initiated a final Synthesis and Modeling Project (SMP), to build on and integrate these data sets in order to address the key scientific themes of JGOFS:

• determine the processes controlling the oceanic carbon cycle and ocean-atmosphere carbon fluxes
• develop improved capabilities for predicting future changes.

Specifically, the central objective of the SMP was to synthesize knowledge gained from U.S. JGOFS and related studies into a set of models to reflect the current understanding of the ocean carbon cycle and its associated uncertainties (U.S. JGOFS, 1997). The SMP was tasked to address not only the processes that control carbon partitioning among oceanic reservoirs, but also the implications for ocean/atmosphere carbon exchange. Both data synthesis and modeling proposals were encouraged with an emphasis on coordinated interaction between the two. The major elements of the program included:

• Individual PI level projects
• Topical Working Groups
• Project management team (two co-coordinators and a project scientist)
• Data management (both distributed and centralized)
• Community activities (PI meetings, mini-workshops, special issues etc.).

The SMP became a full fledged program with the funding of the first SMP awards in early 1998. Funding for SMP grants was provided by the National Science Foundation (NSF), the National Aeronautical and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), and Department of Energy (DOE).

PROGRAM SCOPE

Specific projects within the SMP fell into two broad categories: data synthesis and extrapolation, and modeling. There was considerable (and necessary) overlap between the two, and the overview of the projects provided below is certainly a simplification of the collective efforts of the individual researchers (details on individual SMP grants can be found at http://usjgofs.whoi.edu/mzweb/syn-mod.htm). The scope and balance of the SMP was based on geographic region of study and investigation of biogeochemical processes.

Synthesis and Modeling Projects

The U.S. JGOFS SMP continued through the 2003-2004 time frame. As the program matured and specific initial projects were completed, the foci for the program was refined to emphasize both emerging new scientific directions and remaining unfinished elements of the original implementation plan. The SMP together with the U.S. JGOFS Steering Committee periodically assessed the program with regard to future priorities. During the active research phase, these are some of the topics identified as filling critical gaps for SMP science:

1. synthesis of primary production, new production and export production (both particulate and dissolved)
2. the mechanisms and rates of mid to deep water particle flux and remineralization as well as sediment diagenesis
3. controls and distributions of calcium carbonate and silica production, transport and remineralization
4. biogeochemical effects of trace metal cycling
5. spatial and temporal extrapolation of biogeochemical flux estimates (e.g. export production) from local to basin and global scales
6. development, evaluation and incorporation of mechanistically based, biological models for global carbon cycle simulations
7. synthesis and modeling studies of the Arabian Sea, Southern Ocean, North Atlantic, ocean margins (with respect to the role of each in basin to global-scale carbon cycle), and the set of U.S. and international time-series stations data.

At the local to regional scale, a series of data synthesis and food web modeling investigations explored aspects of euphotic zone production, recycling, export, transport and remineralization, and sediment cycling using the JGOFS process and time-series data base and related data sets. Individual projects concentrated, for example, on subsets of the overall JGOFS data (e.g. bacteria, mesozooplankton, HPLC pigments). Related projects focused on the distribution and dynamics of planktonic functional groups (e.g. N₂ fixers, diatoms, calcifiers). The eventual aim of many of these food web related studies was to extrapolate the findings to basin and global scale and/or to develop improved process-based parameterizations that could be incorporated into regional and global models.

One or more regional ecosystem modeling studies were undertaken for each of the following U.S. process/time-series study locations: Equatorial Pacific and Atlantic, Arabian Sea, Ross Sea, Bermuda, and North Atlantic. Additionally, there were four projects which concentrated on data synthesis and/or modeling for various continental margins: NW Atlantic margin, southern Caribbean, Cariaco Basin, and several coastal upwelling regions. The regional synthesis and modeling studies as well as some of the food web projects relied heavily on satellite data. Many SMP projects utilized satellite data, in particular SeaWiFS ocean color, as an integral part of both model evaluation and time/space extrapolation.

On the global perspective, over a dozen synthesis groups worked on the JGOFS/WOCE global CO₂ survey data with good coverage for all of the carbon related parameters (DIC, alkalinity, ¹³C, ¹⁴C, nutrients, oxygen, pCO₂, etc.). A coordinated global biogeochemical modeling effort was initiated as part of the international Ocean Carbon Model Intercomparison Project (OCMIP, http://www.ipsl.jussieu.fr/OCMIP/). As the name implies, this was an observation-based evaluation of some thirteen global ocean biogeochemical models of the natural and anthropogenic inorganic carbon system, biogeochemical fields (nutrients, oxygen), and related passive chemical tracers (e.g. CFCs, ¹⁴C, ³He).

Links to Related Programs Subsequent to US JGOFS SMP:

Ocean Carbon & Biogeochemistry (OCB)
North American Carbon Program (NACP) Coastal Synthesis
 

The United States Joint Global Ocean Flux Study was a national component of international JGOFS and an integral part of global climate change research.

The U.S. launched the Joint Global Ocean Flux Study (JGOFS) in the late 1980s to study the ocean carbon cycle. An ambitious goal was set to understand the controls on the concentrations and fluxes of carbon and associated nutrients in the ocean. A new field of ocean biogeochemistry emerged with an emphasis on quality measurements of carbon system parameters and interdisciplinary field studies of the biological, chemical and physical process which control the ocean carbon cycle. As we studied ocean biogeochemistry, we learned that our simple views of carbon uptake and transport were severely limited, and a new "wave" of ocean science was born. U.S. JGOFS has been supported primarily by the U.S. National Science Foundation in collaboration with the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the Department of Energy and the Office of Naval Research. U.S. JGOFS, ended in 2005 with the conclusion of the Synthesis and Modeling Project (SMP).