U.S. JGOFS SMP Summer Meeting Report July 22-26, 2002 Woods Hole, MA Scott C. Doney and Joan A. Kleypas

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Note:  this is the version prepared for the US JGOFS Newsletter vol 12, no. 1
(Thanks to Mardi Bowles for her professional editorial assistance.)
 

U.S. JGOFS Synthesis and Modeling Project (SMP) investigators held their fifth annual summer workshop at the Woods Hole Oceanographic Institution (WHOI) in July. Our reports on these meetings track not only the scientific advances of the project but also the progress of the SMP "experiment," which has brought together scientists from an extraordinary range of oceanographic disciplines. An overwhelming conclusion of this meeting, the last of the big SMP workshops, is that the SMP is succeeding in fostering beneficial collaborations among individual investigators and helping to reshape the overall approach to ocean carbon-cycle science.

    More than 90 participants attended the meeting, which followed a format like that of the Gordon Conferences. The meeting was organized around four plenary sessions: The Southern Ocean - Paleo and Present, Food Webs, Global-Scale Synthesis of the Carbon Cycle, and SMP Goals and Accomplishments. The format allowed ample time for free-wheeling discussion. The SMP Goals and Accomplishments session, led by David Siegel of the University of California at Santa Barbara (UCSB), Hugh Ducklow of the Virginia Institute of Marine Science and Robert Key of Princeton University, provided an interesting assessment of SMP progress towards its overall goal of synthesizing knowledge gained from U.S. JGOFS and related studies into models that reflect the current understanding of the ocean carbon cycle and its uncertainties. A breakdown of SMP projects within disciplinary and geographic categories (Table 1) shows that the program has broadly addressed the first two main elements: global and regional mass balances, and mechanistic controls on local carbon balances. The third element, extrapolation, monitoring and prediction, builds on the first two elements and has yet to be tackled decisively.

    During the workshop, John Dunne of Princeton conducted an informal but imaginative survey among the participants. He asked three questions:

• What is the major contribution of JGOFS to ocean biogeochemical modeling?
• What is the major change in thought since the SMP Implementation Plan?
• What is the most pressing uncertainty in biogeochemical modeling?

Science Highlights

In the Global-Scale Synthesis session, complementary talks on anthropogenic carbon dioxide (CO2) by Nicolas Gruber of the University of California at Los Angeles and Christopher Sabine of the University of Washington highlighted the strong dependencies between observations and modeling. Sabine's total ocean inventory estimate (102 ± 6 Pg C for the period from the pre-industrial through 1994) is based on a synthesis of the global data set amassed by JGOFS investigators on World Ocean Circulation Experiment (WOCE) hydrographic sections. It provides a high-quality baseline against which future increases in anthropogenic CO2 in the ocean can be measured.

    Gruber presented a summary of the Ocean Carbon Model Intercomparison Project (OCMIP), which produced a somewhat higher estimate (121 ± 12 Pg C for the period through 1990). The OCMIP simulations, along with inverse modeling results, also show broad agreement on how carbon uptake varies regionally. For example, oceans south of 36°S appear to be responsible for about 40% of the global ocean uptake of anthropogenic CO2.

    Reiner Schlitzer of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, presented an ocean inverse calculation in which biogeochemical flux estimates were derived from observed large-scale inorganic carbon, oxygen and nutrient fields and the flow field from a circulation model (see article in this issue). His model demonstrated remarkable skill at reproducing observations of marine productivity, particle fluxes, remineralization rates and air-sea gas exchange rates over most of the globe. The main differences occurred in the Southern Ocean, where simulated export production is much higher than satellite-based estimates. Biogeochemical inverse models, likely to become more widespread in the future, depend on having high-quality, publicly-available data sets such as the one collected during the global CO2 survey.

    Robert Anderson of Lamont-Doherty Earth Observatory introduced the Southern Ocean -Paleo and Present session with a talk on how light, grazing, iron and silica limit productivity over the seasonal cycle in the Antarctic Circumpolar Current. He showed that different factors exert control over growth, biomass, community structure and export from season to season and place to place.

    Roger François of WHOI followed with a presentation on the hypothesis that higher Southern Ocean productivity during the last glacial maximum (LGM) led to a reduction in atmospheric CO2. Data from sedimentary cores, including measurements of clay flux, diatom assemblages, nitrogen isotope ratios, ratios of cadmium to calcium, and biogenic barium accumulation, provide equivocal results. But François argued that increases in iron could have allowed higher seasonal drawdown of nutrients in the extended glacial seasonal ice zone.

    Keith Moore of the University of California at Irvine discussed model simulations in which increased levels of iron in wind-borne dust during the LGM enhanced primary production south of 30°S by as much as 50% and the export of particulate organic carbon by more than double current levels. Plenary discussion highlighted the potential role of multi-element limitation, cellular composition and functional group dynamics. A particular example raised by Jorge Sarmiento and Katsumi Matsumoto of Princeton and Mark Brzezinski of UCSB suggests that elevated levels of iron during glacial periods shift Southern Ocean diatom ratios of silicon to nitrogen, leading to substantial export of silicon to the rest of the ocean and correspondingly large changes in the carbon cycle.

    David Karl of the University of Hawaii and Paul Falkowski of Rutgers University presented fascinating plenary talks on the importance of biological detail in determining ecosystem function and response during the Food Webs session, organized by Edward Laws of the University of Hawaii and Raleigh Hood of Horn Point Laboratory. Karl argued for a resounding "yes" to the question posed by Richard Eppley in 1984: Do we need to know the full natural history of the plankton to satisfy JGOFS objectives? Falkowski and Karl highlighted the ecological importance of a wide-ranging set of factors, including viruses, vitamins, evolutionary history and genomics, and unusual microbial physiologies.

Final Phase of the SMP

Funds were awarded for a final five SMP grants this year, bringing the total to 65. The focus of the program is now shifting toward the orchestration of a larger-scale synthesis of the ocean carbon cycle. Considerable effort has already gone into various community projects. Examples include the merged U.S. JGOFS process study data products and the on-line data retrieval system developed through the joint efforts of the U.S JGOFS Data Management Office staff and investigators at the University of Washington and the NOAA Pacific Marine Environmental Laboratory. Other projects include the global synthesis of ocean carbonate system parameters and nutrients coordinated by the Global Ocean Data Analysis Project (GLODAP) group. The SMP is also producing a series of research paper collections in issues of Deep-Sea Research II. The first volume was published in early 2002, and a second is expected in mid-2003.

    With two more years remaining, SMP participants are interested in producing tangible results beyond data archives and journal papers. A variety of ideas have been put forward. These include articles for broader audiences on the ocean carbon cycle, a marine ecological modeling "tool bench," educational materials for primary and secondary-school students as well as undergraduate and graduate students, an intercomparison of state-of-the-art ecosystem models in one or more ocean general circulation models, experiments designed for future ocean observing networks, and climate-change scenarios. One idea with strong support is to use the 2003 summer meeting as the basis for a set of review papers on ocean carbon-cycle synthesis and modeling.

    More information about the 2002 summer meeting is available via the U.S. JGOFS home page (http://usjgofs.whoi.edu/mzweb/whoi_agenda_2002.html). Many of the plenary talks are available via this page. The 2003 summer meeting will be held in Woods Hole July 21-25.

Table 1: Summary of US JGOFS Synthesis and Modeling Funded Projects by approach, geographic distribution, process and data sources. Note that some projects fit into multiple categories.

Total Number of Projects		65
Main Approach:
Synthesis		22
Modeling		33
Remote Sensing		8
SMP Management		2
Geographic Distribution:
Global Synthesis		17
Global Modeling		7
Regional Synthesis and Modeling		27
HOT & BATS Time-series	3
Arabian Sea	1
Equatorial Pacific	2
Southern Ocean	4
North Atlantic	4
Pacific	3
Tropical Pacific & Atlantic	3
Multiple JGOFS Sites	2
Subtropical/Subpolar Gyres	1
Ocean Margins	4
Process:
Biological/Physical Interactions		9
Euphotic Zone Production and Export		16
Subsurface Transport/Remineralization		6
Sediments		3
Projects using data from:
Global survey & climatological data		19
Time-series measurements		9
Process studies		14
Satellite ocean color		13
General JGOFS and other data		18