Community Synthesis and Modeling

Group Leaders: Mick Follows and Scott Doney

Objective:To provide a unifying framework for the overall JGOFS synthesis of the marine carbon cycle, up to and including the development of community ocean biogeochemical models.

Background: The overall synthesis of JGOFS SMP should provide:

• our best state estimate for the global marine carbon cycle including fields, rates, transports, and governing processes;
• a community resource base of observational data, synthetic products and models that can be built upon by post-JGOFS researchers;
• an organizational framework for ongoing SMP activities.

A multi-faceted approach is called for that builds on and integrates the common SMP activities identified at the PI meeting. The present OCMIP (Ocean Carbon Model Intercomparison Project) can be viewed as our first attempt to constrain global carbon cycle models with relatively crude biology. The next step of the progression would be a community effort to compare and validate global ecosystem models (an OEMIP if you want). For that we need many of the products of the other SMP working groups, namely: improved, tested ocean circulation models (OCMIP); better biological process models (regional test beds); global validation data sets beyond what are currently available (large-data sets); and tools for spatial extrapolation of ocean biogeochemical fields for diagnosing and monitoring seasonal and inter-annual variability of ocean biogeochemical fields (biogeochemical remote sensing). A set of "community" models and best state estimates of the carbon cycle would be natural outcomes of such an effort.

Tasks: Over the next year, the working group will hold discussions primarily via email on the shape of the final synthesis and how best to attain it. The overall JGOFS legacy will include:

• the JGOFS field data itself (CO2 survey; time-series; process studies),
• all of the PI lead research papers and special volumes,
• documentation of the scientific advances both in terms of conceptual synthesis and modeling (e.g., a Cambridge textbook like approach with invited review chapters on 10-20 topics),
• a set of local (1-D) and regional model test beds with the associated data sets,
• a global ocean atlas with observed and synthetic fields (e.g., in addition to those fields used for OCMIP including: satellite data; historical deep-traps; floristic and community structure estimates; bottle chlorophyll),
• a set of validated global diagnostic and prognostic models.
  

Members: Mick Follows, Scott Doney, Rob DeConto, Jorge Sarmiento, Rick Murnane

Global-Scale Biogeochemistry

Group Leaders: Ed Laws and Ray Najjar

Objective: The goal of the biogeochemical modeling effort is to develop a model of carbon cycling in the ocean that simulates relevant characteristics of pelagic food webs and organic matter decomposition. Those characteristics should be incorporated into a global circulation model (GCM) that simulates the movement of carbon within the ocean and the exchange of CO2 between the ocean and atmosphere.

Background: Important aspects of the modeling effort will involve the identification of factors that limit photosynthetic rates at different times and places in the ocean and the relationship between the supply of those limiting factors and new and total production. Other aspects of the biological system that need to be simulated include: remineralization, diatom production, which is closely related to export production in many parts of the ocean, and the contribution of calcification to inorganic carbon assimilation. An important constraint on the modeling effort is the need to develop a biological component that correctly simulates the important/relevant characteristics of carbon dynamics as influenced by biological processes without becoming so complex that incorporation into a GCM model becomes impractical.

Tasks: The proposed treatment of marine biogeochemistry in the Ocean Carbon Model Intercomparison Project (OCMIP) is relatively crude. The short-term task for this working group is to create a more robust set of parameterizations to include in the first round of OCMIP simulations for fall/winter 1998.

Membership: Edward Laws (University of Hawaii at Manoa)
Ray Najjar (Pennsylvania State University)
Ken Caldeira (Lawrence Livermore National Laboratory)
Richard Barber (Duke University Marine Laboratory)
Robert DeConto (National Center for Atmospheric Research)

Continental Margins

Group Leader: Frank Muller-Karger

Objective: To assess the role of the ocean margins and pelagic-margin exchange in the global carbon cycle and to lay the ground work for incorporating the coastal environment into general circulation models.

Background: The importance of continental margins in the global and marine carbon cycles has been pointed out in peer-reviewed publications (e.g., by authors like Walsh, Jahnke, and others). It is important that these regions, and the very active physical and biological processes that take place there, be represented in global assessments for which GCMs and coupled biological models are being used. Thus these processes should be incorporated into the newer GCMs at the proper space and time scales. Although the primary emphasis of the U. S. JGOFS SMP is on the pelagic carbon cycle, the SMP can provide leadership in this area through the continental margin working group via communication with the coastal, pelagic and GCM modeling communities.

Tasks: The continental margins working group plans to convene a small meeting of experts (5-6 people) from both within and outside the JGOFS community in the Fall to address the following issues:

• develop an operational definition of continental margins;
• provide a first-order estimate of the importance of continental margins in the global carbon cycle, including the effect of neglecting these regions in global GCMs;
• define a strategy for improving assessments of the coastal ocean using in-situ data, remote sensing, and models;
• outline a method for incorporating ocean margins into the next generation of global GCMs.
  
  
  

Large-scale Data Sets

Group Leaders: Ralph Keeling and Chris Sabine

Objective: To encourage the completion of data quality, synthesis and archiving activities on large-scale ocean data sets (e.g., global CO2 survey) relevant to the goals of SMP and to ensure uniform data access to those data sets and derived products.

Background: The working group identified a variety of activities that are only marginally (if at all) represented within JGOFS-SMP funded investigations, but which are needed to fulfill the overall goals of SMP.

• A coordinated analysis of the WOCE/JGOFS carbon-system data to place the relevant variables (DIC, ALK, pCO2, and pH) on a "consistent basis". Not all of these were measured on all cruises, but in principle they can be computed for all cruises where at least two were measured. A uniform dataset for these variables is needed for a wide range of potential JGOFS-related research activities.
• A coordinated analysis/syntheses of other WOCE/JGOFS hydrographic data including but not restricted to isotopic, nutrient, and transient tracer data. Included in such activities are generation of generally useful derivative fields, such as "anthropogenic CO2" or pre-bomb 14C, etc.
• Studies which compute the fluxes of various chemical quantities across hydrographic sections. Such studies might profitably be linked with studies of fluxes (e.g., of CO2) across the air-sea interface and with inventory studies. A global joint synthesis of transports, air-sea fluxes, and inventory changes should be viewed as one of the tangible long-term goals of JGOFS SMP but with strong ties to the WOCE program.
• Studies which can address how best to correct upper ocean data sets for seasonal variations in order to assess long-term trends.
• The need to tie in all of the process study and time-series data into the large-scale observational program. The working group believes the SMP should encourage a unification of the process studies, time-series, and global survey data to specifically address point #5. The PI meeting was a great step forward in unifying the modelers, but a similar approach should be taken to unify the individual measurement programs sponsored through JGOFS (including international cooperation).

Tasks: Open discussions with other data facilities including the WOCE hydrographic office and CDIAC to develop a seamless data system. This system will be needed for many research activities both within and outside of JGOFS-SMP. The generation of this data system would eventually help to avoid duplicated effort. We envision that such a system would provide consistent carbon-system data, discussed above, and other hydrographic data, such as self-consistent nutrients, O2, 13C, 14C, transient tracers, and "product" fields, such as "anthropogenic CO2," or pre bomb 14C, etc.

We suggest that a positive development would be securing some core support from within JGOFS SMP to establish and manage such a data system. Whether this data system would be housed at WHOI, through CDIAC, or elsewhere, we suggest that some "core" support would be beneficial in providing critical management infrastructure, and in communicating to a larger community (including funding agencies), JGOFS-SMP intent to serve as a central program for facilitating and coordinating research on large-scale chemical datasets.

Membership: Bob Bacastow, Chris Sabine, Ralph Keeling, Scott Doney.

Satellite Biogeochemistry

Group Leader: Mary-Elena Carr

Objective: The long term goals are to obtain four-dimensional analysis fields for the ocean based on satellite data and model output and to strengthen and maintain the relationship between the remote sensing community and the JGOFS science team.

Background: Remotely sensed observations provide a unique contribution towards the objectives of JGOFS SMP because of their high spatial and temporal resolution. This can serve to validate model output beyond the capabilities of ship-board observations as well as helping to identify areas that are important but not well resolved by models (such as the polar regions and continental margins). Empirical numerical models are equally important to convert primary production estimates from satellite data into export production, the key variable for JGOFS SMP. It is recommended that the NASA Primary Productivity Working Group efforts (which aim to improve the estimate of total production from space) be made readily available to the JGOFS community.

Research fields that are "missing" or aren't solved yet include:

• an estimate of the role of the continental margins in global CO2 cycles,
• pCO2 from space,
• color CDOM to DOC,
• export production estimates from space, e.g.,
  - nitrogen budgets
  - eddy activity and pumping
• piston velocity estimates from scatterometer,
• identification algorithms for phytoplankton with differing biogeochemical needs e.g.,
  -Calcifiers (coccolithophores): discrimination algorithm exists
  -Nitrogen fixers (trichodesmium): discrimination algorithm exists
  -Silica users (diatoms): no discrimination algorithm yet, size-based?
  -Junk species (red tides/phaeocystis/etc.): maybe?

Tasks:

• Improve availability to SMP community of relevant remotely sensed fields (e.g., light fields (PAR), diffuse attenuation coefficient (K_PAR), sea ice extent, sub-grid scale variance for "coarse resolution" (1-4deg) models);
• Encourage the merging of the various ocean color sensors via SIMBIOS;
• Ensure that remote sensing community is aware of availability of JGOFS field data for validation and assimilation;
• Expand bio-optical matchup data to include CO2 data;
• Encourage development of new algorithms to account for missing derived fields (listed above) needed to estimate biogeochemical fluxes.

Each NASA-funded SMP proposal is an Earth Observing System (EOS) Interdisciplinary Science (IDS) Team. It is important that we exercise our voice in the EOS community. It is recommended that we ensure participation and visibility in upcoming EOS Investigators Working Group (IWG) meetings.

Nitrogen Fixation

Group Leader: Doug Capone

Objective: To promote the improved understanding of nitrogen fixation at the process level and to incorporate that knowledge into predictive parameterizations for local, regional and global models.

Background: Growing evidence suggests that nitrogen fixation plays a key biogeochemical role in the subtropical oceans and that the overall fixation rates may be significantly larger than previously thought. This working group is built around a core of SMP investigators, funded under Doug Capone's grant to study nitrogen fixation, and other interested individuals including several from the global modeling groups. The goals of the group are to:

• Promote interaction of field biologists studying N2 fixation and modelers;
• Specifically discuss controls on marine N2 fixation and appropriate modeling approaches;
• Discuss anomalies in existing data and identify critical data gaps;
• Discuss coupling satellite remote sensing with modeling efforts;
• Develop data bases and provide access to data sets on oceanic N2 fixation for model calibration/ verification;
• Consider physiological as well as geochemical approaches to modeling marine N2 fixation;

Tasks:

• An initial workshop will be scheduled for late this fall or early next spring. It would most likely be in the Chesapeake region as we only have limited resources to support travel of our PIs.
• Provide and interface between the JGOFS SMP program and the upcoming series of SCOPE workshops on global and marine N2 fixation and modeling to be held this Fall and next spring.

Membership: Core participants are Doug Capone, R. Hood (UMCES/UMD), J. Montoya (Harvard/ Ga.Tech), E.J. Carpenter (MSRC/ SUNY) and A. Subramaniam (CBL/ UMCES). R. Armstrong and J. Sarmiento et al. (Princeton) have indicated interest in participating. Other possible participants are J. Zehr (RPI), F. Lipschultz (BBSR), P. Falkowski (Rutgers).

Regional Testbeds

Group Leader: Rob Armstrong

Objectives: To create regional data sets, including physical, chemical, and biological data, to be used for evaluating ecosystem models. The regions of interest initially include the U.S. JGOFS time-series sites (HOT and BATS) and process-study sites (NABE, EqPac; Arabian Sea; Southern Ocean), but could be expanded to other sites as well. The approach will be incremental, starting with the Equatorial Pacific and expanding as we gain more experience.

Background: There are two motivations for the creation of regional testbeds: 1) it is desirable to have a forum in which different models and modeling approaches can be compared to common data sets, so that the strengths and weaknesses of these approaches can be compared; and 2) it is only by making such comparisons on a regional basis that we will be able to decide whether it is possible to create a single model structure, with parameter values that are generated regionally in response to environmental forcings, or whether an approach based on dividing the world a priori into biogeochemical provinces is the only way to handle the different characteristics of different regions. The aim therefore is to provide a forum within which diverse models can be compared over several regions. It may turn out, for example, that vastly different model structures are required in different regions; or it may turn out that a single model structure, with minor (self-generated) parameter changes, performs well over a range of regions, though perhaps not being the best model in any one region.

This effort builds on efforts at model intercomparison initiated at the International JGOFS workshop in Toulouse, France, in November 1995. At that workshop, several ecosystem models were compared in relation to a common data set from the subarctic Pacific. The structure we envision for U.S. JGOFS Regional Testbeds differs fundamentally from this "workshop" approach in that the evaluation of models will be distributed in time and space.

Individual investigators will be able to access a common data base and common physical model, and will be able to tune their models to these data. Comparisons between the performances of different models will initially be made on an informal basis among participants, though as the project progresses it may be desirable to create a more formal forum for model intercomparison, perhaps in conjunction with a yearly JGOFS SMP summer meeting. The informality of the process, and the ability of investigators to experiment with their models, should relieve the idea that this project is a shootout among existing models, the winner of which will be crowned an official JGOFS-sanctioned model.

Tasks: For the Regional Testbeds project to be successful, the assembling of these regional testbeds must not fall as an onerous task on any individual or group of individuals. For this reason, our plan is to rely on individuals who have worked on coupled physical-biological models of various regions, asking them to share with the community the data sets and physical models they have used in developing their ecosystem models.

For the first regional testbed, on the Equatorial Pacific, Fei Chai, Mark Verschell, and Mike Roman have agreed to collaborate to design the testbed, both by assembling appropriate data sets and by establishing a common physical model (the plan is to have both 1D and 3D physical platforms).

They will provide information for two different longitudes, since a model that requires vastly different parameter values to perform well even within the same region is probably not a very good model. As we gain experience with the process, other regions will be added; Raleigh Hood, for example, expressed interest in developing an Arabian Sea testbed; we hope others will join the effort as it progresses.

Membership:
Rob Armstrong
Nick Bates
Adrian Burd
Fei Chai
Dick Dugdale
Raleigh Hood
George Jackson
Ed Kearns
Mike Roman
Mark Verschell