U.S. JGOFS SMP Summer Meeting Report
July 16-20, 2001
Woods Hole, MA
Scott C. Doney and Joan A. Kleypas

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Note:  this is the initial., and longer version of a report prepared for the US JGOFS Newsletter.

 The U.S. JGOFS Synthesis and Modeling Project (SMP) held its 4th annual Principle Investigator meeting at Woods Hole Oceanographic Institution (WHOI) in July. About 80 persons attended the meeting, most of which are SMP investigators and associated students and postdocs. The list also included two invited speakers (Taro Takahashi and Jim Bishop) and Don Rice from NSF.

The SMP is just beyond the peak of it's funding cycle (Figure 1), with 38 active projects, and 22 completed. Results from many of the synthesis and modeling efforts are just now coming forth, and the emphasis at this meeting was to provide a forum for investigators to share their project results or plans with other PIs. Short talks were organized into 7 main topics, and although only a few highlights are presented here, abstracts for all talks and posters can be viewed at http://usjgofs.whoi.edu/mzweb/whoi_agenda_2001.html.

Fig. 1. Number of SMP Projects Funded per year. Note that number of projects funded for FY2002 is estimated at 5.

Euphotic Zone Production and Export. The euphotic zone is well represented in the SMP, with about 17 projects researching largely biological processes within this zone. Talks ranged from theory (Ed Laws' historical perspective energy flow through ecosystems); to ecosystem control of Redfield ratios (Michael Lizotte's HPLC results that show how a dominant phytoplankton taxon can exert characteristic nutrient drawdown and Redfield ratios; Jim Christian showed how variable C:N:P stoichiometry in models can explain how cellular N and P quotas can indicate P limitation when the inorganic pool suggests N limitation); to mesoplankton production (Mike Roman's interesting explanations as to why mesoplankton production at BATS is lower than at HOT, even though primary production at the two sites is similar).

Twilight Zone through Sediments and Continental Margins. These regions are perhaps the most poorly characterized in terms of their role in the ocean carbon cycle. Talks within this session highlighted intriguing questions surrounding export and subsequent remineralization. Ken Buesseler offered explanations for the mismatch of export flux measured in traps vs. 234Th measurements, and George Jackson used modeling results to show that particle aggregation could explain how a significant portion of export can occur in pulse events. Organic matter remineralization in sediments was addressed by Bill Martin. His model determines the depth of CaCO3dissolution as a function of organic matter rain rate. At higher rates, oxidation rates increase and occur closer to the sediment/water interface, so that diffusion from the overlying water column dominates the neutralization process. This implies that high organic rain rates actually inhibit rather than enhance CaCO3 dissolution in sediments, as previously thought. Rick Jahnke's global comparison of satellite-derived surface production with seafloor O2 flux revealed some contradictory patterns. One is that the high fluxes of the Equatorial Pacific are not reflected in the sediments. Another is that the transfer efficiency of organic carbon to sediments ranges dramatically between regions: low latitudes show much higher efficiency than high latitudes; and efficiency along continental margins is 50( greater than within gyres. Continental margins were also highlighted by Jim Bauer, who presented the main results of the Ocean Margins Program synthesis, that: 1) the NW Atlantic margin is a net sink for CO2; 2) much of the DOC and POC in shelf/shallow slope waters has both marine and terrestrial origins; and 3) 80% of the shelf to open ocean export is in the form of DOC. Satellite Data & Basin-scale Biogeochemical Modeling. All of the NASA-funded projects are now complete, and many talks at the meeting relied heavily on SeaWiFS and other satellite data. Mary-Elena Carr compared CO2 exchange coefficients derived from two wind sensors: SSM/I (wind-speed only, 13 year time-series) and QuickScat (improved wind-speed plus wind-direction, 1 year time-series). And Jim Yoder presented a new 3-year, global SeaWiFS-derived chlorophyll dataset at 8-day resolution (see: http://www.po.gso.uri.edu/~maureen/sm_seawifs.html). Jim's EOF analysis of these data showed that 6 modes (season, ENSO, etc) explain 70% of the variability within the ocean chlorophyll patterns. Dave Siegel also used SeaWiFS imagery, combined with field and model data, to test Sverdrup's spring bloom hypothesis that phytoplankton bloom in response to the critical depth (MLD/ED). Although satellite data show a poleward progression of the spring bloom, it was not strongly correlated with critical depth; so either the mixed layer depths are wrong, the bloom indices are inappropriate, or MLD/ED is not a good representation of critical depth. Mick Follows looked specifically for factors associated with the North Atlantic spring bloom, and showed that subtropical blooms do appear to respond to enhanced mixing, while subpolar blooms are largely modulated by factors such as changes in insolation, local mesoscale variability, and grazing. Niki Gruber demonstrated, with a box model, how the NAO influences CO2 uptake in the North Atlantic. He feels that during negative NAO, weak winter convection in subpolar gyres leads to higher uptake of atmospheric CO2 because less DIC is entrained from deeper waters, and also because more biological drawdown occurs during the following spring/summer.

Marine Calcification and Silica Cycling. The SMP Workshop "Marine Calcification" held this past spring, re-asserted that CaCO3 as well as silica plays a vital role in marine carbon cycle, and several talks at this summer's meeting focused on these two biominerals. Two major findings presented in this session are that up to 70% of CaCO3 produced in the euphotic zone is dissolved above the calcite lysocline (Dick Feely's analysis of the Pacific CO2 survey data); and that the CCaCO3:Corg ratio necessary to produce present day alkalinity distribution in ocean biogeochemical models is probably much lower than is typically used (Jorge Sarmiento). The potential effect of silica on the global carbon cycle was illustrated by Katsumi Matsumoto. His box-model results show how reduced silicic acid uptake in the southern ocean since the LGM could have led to increased silica supply to other oceans ("leakage"), and that eliminating silica limitation could dictate a community shift from CaCO3 to silicate-dominated systems (and a shift in the CCaCO3:Corg ratio).

Global Scale Data Synthesis. Each SMP meeting has served as a show-case for newly compiled global data sets. Besides the compilations already mentioned by Yoder and Feely, several other projects announced new products: Chris Sabine provided an update of the Global CO2 Synthesis, which is now complete for the Indian and Pacific Oceans, and well underway for the Atlantic. Paulette Murphy summarized the ongoing synthesis of carbon system parameters into a global database that includes historical data as well as the CO2 Survey data, and Alexy Mishonov and Wilf Gardner provided the latest updates on the POC data base (see http://www-ocean.tamu.edu/~pdgroup/DataDir/SMP-data.html).

Modeling CO2 Transport. Understanding oceanic CO2 transport is essential in both atmospheric and oceanic studies of the global carbon cycle. Along these lines, Alison Macdonald presented an analysis of CO2 transport across 24.5°N latitude, illustrating that that southward transport of carbon in the Atlantic has weakened since the preindustrial. Paul Robbins also addressed the question of meridional carbon transport with the intriguing question: "Where is the 'Carbon Equator'?", and pointed out that a major difficulty with understanding interhemispheric carbon transport relates to an offset in the atmospheric "equator" (effectively the ITCZ) and oceanic equator (true equator).

Global Scale Modeling. Mick Follows presented a nice analysis of why GCMs show a higher sensitivity of pCO2 to low latitude perturbations than do box models. He concluded that the difference is largely due to the absence of wind-driven circulation in box models. Watson Gregg used a coupled, 3-D GCM/biogeochemistry/radiative model to examine how changes in cloud cover and liquid water path (LWP) might affect primary production. Doubling the LWP in the model had little effect on community structure, but lowered primary production by up to 10%, with the strongest reductions at higher latitudes.

Two talks presented results from multiple global-scale models. Ray Najjar's presentation of OCMIP results showed progress on the analysis and interpretation of a suite of tracer and carbon-cycle simulations among a dozen general circulation models. Striking differences in the physical circulation of the models show up in the predicted patterns of chlorofluorocarbon (CFC) and anthropogenic carbon uptake and the global integral of new production. Jorge Sarmiento summarized the results of coupled climate simulations of both present-day and future scenarios from six different models, with emphasis on how future changes in ocean circulation will affect marine ecosystems. He concluded that decreased upwelling along western boundary currents and increased stratification in subtropical gyres will cause decreased biological production in the future; whereas higher latitudes may have increased production due to increases in dust-borne micronutrients. Predictions are difficult for equatorial regions, where nutrient supply mechanisms are poorly understood.

Scott Doney looked at CFC-11 distribution in various GCMs to examine how each handles deep water formation of Antarctic Bottom Water. He discussed how incorporation of a simple bottom boundary layer scheme in the NCAR ocean model (combined with small adjustments in the surface restoring salinities) improved the deep water distribution of CFC-11.

Invited Talks. This year, the SMP meeting included two invited speakers: Taro Takahashi and Jim Bishop. Taro Takahashi provided a new estimate of global ocean uptake flux of CO2 (observed (TC - sea-air CO2 flux) of 2.2 (+22% or -19%) PgC y-1. This estimate, which uses the (wind speed)2 dependence of the CO2 gas transfer velocity of Wanninkhof (1992) is consistent with observations of both atmospheric CO2 and O2, while using the (wind speed)3 dependence of Wanninkhof and McGillis (1999) increased the estimate by 70%. Jim Bishop's talk provided a techno-escape from modeling and synthesis papers, in a presentation of new instrumentation that can measure multiple carbon parameters, and can be fitted to existing ARGO floats that transmit data via satellite at programmable intervals. His pilot release of two such fitted floats in the North Pacific, and their fortuitous capture of water parameters during a large atmospheric dust event, provided an exciting glimpse of how remote oceanographic data collection can not only simplify data collection, but improve our understanding of ocean processes with increased ability to sample during extreme weather events.

Data Management. The U.S. JGOFS Data Management Office is now actively collaborating with the University of Washington/PMEL team of Chris Sabine and Steve Hankin, and data management activity has increased significantly over the last year. Cyndy Chandler presented an overview of the many new tools now available for accessing and retrieving JGOFS data, including the creation of "merged" data sets for each of the U.S. JGOFS process studies. These merged data (bottle data, CTD data, etc.) can be displayed, subsampled and downloaded via a new Live Access Server (LAS) capability of displaying discrete data along various dimensions. This supplements the existing JGOFS LAS (http://usjgofs.whoi.edu/las/servlets/dataset) that previously could display gridded data only.

Community Activities & Future Directions. The last round of funding for the SMP will be awarded early in 2002, and considerable discussion surrounded the legacy of the SMP and promoting community activities. Suggestions toward establishing the overall synthesis of the SMP included compilation of major findings in a synthesis book, promoting "high-profile" synthesis papers, and promoting workshops such as those sponsored by the NATO Advanced Study Institute. It was also agreed that more effort would be made to ensure that educators and the general public have access to SMP science. The 2002 SMP annual meeting will likely lean toward a discussion-style format, and will be held July 22-26, once again in Woods Hole.