This document started out as the Implementation Plan for the U.S. JGOFS program. It was designed to build upon the broad scientific objectives laid out in the U.S. JGOFS Science Plan (May, 1990). That plan defined the elements of the research necessary to achieve a major step forward in our understanding of the oceanic carbon cycle and its relationship with climate change.
It has been developed and shaped by the U.S. JGOFS Scientific Steering Committee and represents its consensus view of how the science goals can be prioritized and met. This is, in effect, the outcome of a scientific debate over how to best meet the objectives of JGOFS. The various sections of the document were developed, under the overall direction of the Chairman of the Steering Committee, Otis Brown, RSMAS, University of Miami, by sub-groups of the Steering Committee headed by Section Leaders. These were:
The membership of the various sections is listed in each section. The considerable time and effort that these many busy people donated to the creation of this document is greatly appreciated. Thanks to the dedication of this group, the direction and scope of the U.S. JGOFS program has been defined and charted.
During the development of the document, the Steering Committee recognized the need to build a well thought out synthesis component to the U.S. JGOFS program. Over the life of the program, there will have been a relatively massive investment of resources, both financial and intellectual. The scientific return on this investment can only be realized if the knowledge and data gained during the program are skillfully woven together, in conjunction with appropriate models. The scientific product will then be solidly based as the foundation for the next generation of ocean carbon study. Accordingly, the thread of synthesis runs through the document, and will ultimately tie the program together.
As a plan for implementing U.S. JGOFS science, it was always recognized that various iterations or updates to this document would be required - as the program matures in the light of new knowledge. This version is no exception. However, the appearance of new technologies such as the Internet and the World Wide Web have offered an ideal platform on which to lay out such a document. This opportunity prompted the decision to place this document on the U.S. JGOFS Home Page. This, then, is a true Living Document, which will be updated on-line regularly in response to reassessments made by the Steering Committee.
Comments and questions to this plan should be sent to
U.S. JGOFS Planning and Implementation Office
Individual addresses and phone numbers can be found on the U.S. JGOFS Planning and Implementation Office page on our World Wide Web server.
The U.S. JGOFS Steering Committee wishes to thank the many people who have contributed to the writing and publication of this Mid-Program Strategy for U.S. JGOFS. Their efforts and dedication made this happen and are sincerely and gratefully acknowledged.
U.S. JGOFS Scientific Steering Committee
1.1.1 Purpose of Document
JGOFS grew out of a workshop held by the National Academy of Sciences in Woods Hole in 1984 with broad community participation, which resulted in publication of the document Global Ocean Flux Study. A Steering Group was established as a result of this activity whose goal was to establish a viable scientific effort within the U.S. to examine carbon flux in the ocean and its role in the global carbon system.
An early focus of these efforts was to organize a domestic program focused on carbon flux issues, the Global Ocean Flux Study, initiate work on international analogs, and to develop a consensus in the U.S. community concerning a scientific agenda for such studies. In less than two years, an international program, the Joint Global Ocean Flux Study, endorsed by the Scientific Committee on Ocean Research, and a linked domestic program supported by U.S. federal agencies were in place. Early on it was decided that the ability to accomplish multi- and interdisciplinary research in biogeochemistry needed to be demonstrated, so a pilot process study, the North Atlantic Bloom Experiment, was organized. Simultaneously, a science plan (U.S. Joint Global Ocean Flux Study Long Range Plan) for the enterprise was under development and published in May, 1990.
The science plan is far ranging, in fact it goes beyond looking at the role of carbon in the ocean system. The science plan was written to provide an accurate description of the state of the science and the issues associated with biogeochemical cycling in the ocean, circa its writing. The multitude of issues discussed in the science plan are not easy to resolve. In many cases they demand new approaches to science. These approaches encompass not only the sociology of different disciplines working together, such as physics, chemistry, biology, geology and meteorology, but also need for major advances in ocean observations, conceptual and numerical models of the ocean and our nation's ability to manage the results of such activities.
The present document is the initial version of an evolving Mid-Program Implementation Strategy for the U.S. JGOFS program. It was initially written after the pilot study, the first large-scale process study in the Equatorial Pacific, implementation of the Global CO2 survey, and successful operation of two time-series stations for five years. U.S. JGOFS has elected to follow a variant of `rapid prototyping' in its implementation planning. Rapid prototyping as used by U.S. JGOFS has involved going to the field with early process studies such as the North Atlantic Bloom Experiment to demonstrate multi- and interdisciplinary observing and early synthesis capabilities, elucidate near-term implementation issues, and then, once a workable approach is demonstrated, to codify the overall programmatic implementation based on the early results. While this approach has given clear guidance on process studies and time-series observations, and the large-scale observations effort as part of the WOCE Hydrographic Program (WHP) has given us indicators for survey work, we have had no similar large scale pilot activities in modeling, data management, synthesis. Thus, the reader should view the current version of this plan as reflecting an advanced understanding of currently viable approaches to in-situ studies and slightly more speculative approaches to the other parts of the JGOFS spectrum. Future editions of this plan will address improvements in our understanding in these other parts of the JGOFS program, as well as address the changing fiscal realities.
The goal of the U.S. JGOFS Mid-Life Strategy is to provide a map to guide the program from mid-life to the attainment of its stated goals. In a more general sense, this plan can be viewed as describing planned field efforts through the end of the decade and analysis and synthesis activities continuing through 2003. It is the program's intent that by the end of the millennium it can provide new insights into the oceanic carbon cycle in the context of interactions between biogeochemical, ecological, and physical processes in the ocean. The resulting synthesis of the JGOFS data and process studies' interpretations should advance us towards our stated operational goal:
"To assess more accurately, and understand better the processes controlling, regional to global and seasonal to interannual fluxes of carbon between the atmosphere and ocean interior, and their sensitivity to climate changes" (JGOFS Science Plan).
Within this broad framework stated in the science plan, we have five specific objectives:
1.2 U.S. JGOFS Structure
U.S. JGOFS has developed a five-fold approach to address its implementation. It can be considered as five cooperating, complementary activities. Broadly defined, these efforts are: Large Scale Observations, Time-Series activities, Process Studies, Modeling, and Data Management. For extensive background and a thorough description of each of these areas, the reader is asked to review sections III through VII in the U.S. JGOFS Long Range Plan (May 1990). The following gives summaries of each area.
Large Scale Surveys. Large scale studies of biogeochemical variables in the ocean are sparse. Extant views describe an ocean which is heterogeneous on many scales with the greatest part of the variance at low spatial and temporal frequencies. Unfortunately these large time and space scales are currently the most poorly observed in the ocean. The rationale for the large scale survey component is to provide a composite, basin to global scale, biogeochemical view of the ocean surface, mid-depth and deep waters. During the JGOFS implementation phase specifically we plan to provide seasonal resolution of key biogeochemical parameters on regional and basin scales and to provide a consistent global description of surface pigment, primary production, CO2, and export fluxes and transformations.
Time-series. Prior to JGOFS there were no long term biogeochemical time-series in the oceans. At the mid-life of JGOFS, we now have two five-year records (Hawaii and Bermuda) and the beginnings of a multi-year high latitude record (Kerguelen Island). Resource limitations dictate a limited number of such time-series sites. Such limitations also suggest that future time-series efforts will utilize autonomous observing systems rather than human/ship mediated observations. The objective of the time-series effort is to provide well-sampled seasonal resolution of biogeochemical variability at a limited number of ocean observatories, provide support and background measurements for process-oriented research, as well as test and validate observations for biogeochemical models.
Process Studies. Early on in JGOFS it became clear that many of the links between key biogeochemical parameters were not well understood. The objective of the process studies component is to target key process links in our current models of the oceanic biogeochemical system and enhance our causal understanding of the processes. The goal of process oriented studies is to provide a mechanistic understanding of ocean processes in sufficient detail to predict and simulate biogeochemical fluxes at representative sites in the ocean.
Modeling. Modeling represent the synthesis of our process understanding as well as an approach for testing our current understanding of various biogeochemical cycles. With sufficient development, models can be used to examine sampled strategies for process studies as well as large scale observations. In the near term, models also suggest possible linkages where improved understanding will provide the greatest advantage. U.S. JGOFS views models in all these ways, however, our objective is to provide a useful synthesis of our understanding which can be used for diagnosis of the current ocean role in the carbon system, as well as for future forecasts of the ocean state.
Data Management. Historically, data management of biogeochemical parameters has not had high priority. This has led to minimal catalogs of past data, little exchange of data holdings, and a general lack of confidence in biogeochemical datasets. U.S. JGOFS, by necessity, believes a critical component of U.S. JGOFS implementation strategy is an agile, cost effective, workable data management scheme which facilitates ready sharing of data models, analysis and other knowledge. The objective of the U.S. JGOFS data management activity is to provide a living dataset which is readily accessible during and after U.S. JGOFS and provides sufficient data documentation to permit intercomparison and quality control.
1.3 Specific Goals
U.S. JGOFS, after completion of the Long Range Plan, started a three year sequence of discussions on an implementation plan. Five working groups, composed of U.S. JGOFS Scientific Steering Committee (SSC) members, were established to develop prospectuses in each of the five streams of activity. The prospectuses were then discussed by the whole Steering Committee, changes suggested, and final versions prepared. Following this activity the draft plans were reviewed by an outside panel. At the conclusion of this process, consensus was reached on seven goals for the program.
The operational goals of the U.S. JGOFS implementation plan are to provide:
Currently we believe these goals should be obtainable by the year 2003 and would be a major step towards the previously stated objective.
A rational approach to implementing a large scale program requires a ranked list of priorities. U.S. JGOFS, in concert with the discussions concerning implementation goals, has also developed a set of implementation priorities. These priorities are based on our current understanding of the available resources, activities in each implementation area, needs in each implementation area, and the aforesaid goals. In a linked set of Steering Committee meetings, community input was used to develop a set of priorities for the program. The following are the priorities established by this process:
U.S. JGOFS accords top priority to the creation and implementation of an integrated system of data management analysis, synthesis and numerical modeling which provides the interface between the work at sea, in laboratories and the finished scientific product that we wish to leave as a JGOFS legacy.
A. Technology Implementation
It is clear that the two existing time-series stations, HOT and BATS, cannot alone provide enough information "To determine the response of the ocean carbon system to physical and chemical forcing from subseasonal events to decadal changes." Additional time-series experiments or observations or research being conducted by International JGOFS will provide valuable data, but there remain several crucial regions where no time-series study is underway. These include sites of deep convection, characterized by remote location, extreme seasonal and probably interannual variability and hostile environmental conditions. Time-series data for future major process study sites, including the Arabian Sea and the Southern Ocean, are also a high priority.
The U.S. JGOFS supports only the establishment of autonomous time-series observation sites in the future, because these appear to be the most cost effective approach. The SSC assigns the highest priority to deploying moorings incorporating proven sensors to measure the light field, biomass based on pigment signals, dissolved oxygen concentrations, conductivity and temperature, and current speed and direction, at time-series and process study sites.
Further technology development is needed for the autonomous measurement of pCO2, TCO2, alkalinity, pH, nutrients, primary productivity, and zooplankton abundance; however, these are being adequately funded outside the JGOFS program. The SSC assigns a lower priority to testing newly available sensors at accessible locations, such as the HOT and BATS sites, and to incorporating sensors which operate successfully into process study moorings.
B. Moderate-scale Process Studies
Because JGOFS will have the resources to conduct large-scale process studies in no more than 4 oceanic regions before the year 2000, it is clear that the large-scale process studies alone are not sufficient for the objective "To characterize the present geographical distribution of key biogeochemical properties and rate processes pertinent to the oceanic carbon system." The SSC recognizes that moderate-scale process studies, each requiring $2.5M in total funds could contribute greatly to our understanding of the global distribution of biogeochemical properties. These include but need not be limited to: the role of mesoscale ocean eddies; studies of nutrient sources and demand in the oligotrophic gyres; and follow-up studies of the spring phytoplankton bloom in the North Atlantic. The scientific background for these and other studies is presented in the U.S. JGOFS Long Range Plan. The SSC encourages further discussion on additional candidates for smaller, process-oriented studies.
The U.S. JGOFS program is operating in a budget constrained environment. Resources for the program come from the National Science Foundation (NSF), National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), Office of Naval Research (ONR), and the Department of Energy (DOE). Currently these organizations provide approximately $15M annually for support of the spectrum of U.S. JGOFS activities. These resources are split between process studies ($9M), global surveys ($3M), time-series ($2M), data management ($0.5M), and modeling ($0.5M).
The most significant change implicit in this version of program implementation is a progressive investment shift toward synthesis and modeling over the next eight years. This plan assumes that modeling, synthesis and data management will be supported with increasing investment starting in FY1996 (+$1M) which will plateau in an investment of $8M per year by FY2001. Early investment would be targeted at currently available data sets while later investment would focus on integration of satellite observations (SeaWiFS, ADEOS, EOS/MODIS and EOS/COLOR) and coupled numerical models.
As stated in the Introduction, we expect this plan to be the first of several iterations towards definition of a programmatic structure and implementation which will achieve the stated goals of the program by 2003. We believe that U.S. JGOFS has already made significant progress towards determining and understanding specific processes during spring blooms and in the equatorial ocean which control the time varying fluxes of carbon in the ocean, as well as its exchange with the atmosphere. As this plan will make clear in the following pages new or enhanced effort in a number of our programmatic areas is needed to optimize the use of current data holdings and process insights as well as to answer questions in other biogeochemical regimes of the ocean system. These include development and application of a data management system and of both small and large-scale models coupling biogeochemical processes and ocean physics; implementation of technologies, including autonomous moorings and satellite remote sensing, which can collect long time-series of data over a wider geographic area than is possible using ships; and execution of moderate scale process studies to address significant gaps in global understanding of the oceanic carbon cycle.
During its approximately ten-year observational lifetime, U.S. JGOFS will provide a foundation for determining the response of the ocean carbon system to physical and chemical forcing over time scales ranging up to the sub-decadal. Thus, it is important that JGOFS encourage activities that will lead to continuing progress over the next 10-20 years. Key areas include the implementation of autonomous sensors at sites where intensive ship-based biogeochemical and physical data are available for verification and interpretation of the mooring data. JGOFS can play a leading role in establishing the groundwork for the biogeochemical and bio-optical measurements of the proposed Global Ocean Observing System. Another important activity is ground-truthing, leading to improved interpretation of satellite observations of ocean biogeochemical properties during the SeaWiFS mission. JGOFS will clearly demonstrate the value of satellite-based observations or inferences of biogeochemical properties and should use its accomplishments to support continued satellite observations such as the Earth Observing System (EOS). JGOFS will be the principal model for programs which will support and exploit the next generation of earth-observing sensors.
2.1 Review of Status of Science Plan
The two major JGOFS goals as embodied in the International Science Plan (JGOFS Report No. 5, SCOR, 1990) are:
The sum of these goals lays out as the central aim of the JGOFS program the embodiment of an improved understanding of ocean fluxes of carbon and associated biogenic elements in the form of models. The discussion of modeling in the U. S. JGOFS Long Range Plan (U. S. JGOFS Steering Committee, 1990) begins with a brief summary of the distribution of biologically active chemical compounds in the ocean, concluding that "these observations challenge us to develop models which couple the physical forcing, biological agents of transformation, and chemical substrates so that theories about the ocean's production system can be formulated and tested. Through large-scale models the theories found to work in areas of study can be applied far afield in regions remote to study sites. The legacy of U. S. JGOFS will be the understanding of the system, as encoded in algorithms and models, which will enable us to monitor the state of the ocean in real-time and to predict its future course in an era of climate change." This section of the implementation plan focusses on the combined data synthesis and modeling activities that will be required to meet the overall goals of JGOFS as summarized in these two documents.
The large temporal and spatial dimensions of these goals require dedicated effort to draw together the collective understanding that the JGOFS project is designed to attain. Indeed the argument used to justify incremental funds to pursue components of the U.S. Global Change Research Program, like JGOFS, is that this collective understanding will be greater than the sum of the individual elements. It is unrealistic to assume that all scientists engaged in field aspects of these projects will have comparable interest in or shared commitment to this responsibility. For some participants in JGOFS the individual investigator's primary results of experimentation and observations that make up the process studies, time series stations, and global surveys are of foremost interest. For others the main intellectual challenge is in understanding a larger scale phenomenon, like the central focus of a process study, i.e. a seasonal or interannual event. At the interface of biology and geochemistry within ocean science, there has been relatively little opportunity to develop syntheses and models that approach the scale of the JGOFS effort. No prior project has rivaled the interdisciplinary scope, global coverage, and U.S. investment in JGOFS. Thus the comprehensive scope of the JGOFS science plan requires an unprecedented and systematic commitment to synthesis and modeling.
All investigators play a critical role in the ensemble of synthesis activities when they fully analyze their individually funded efforts and submit these data to the JGOFS data base. In addition, many process study grants were funded with the specific expectation that groups of investigators would be working together to interpret multiple linked data sets. However, the more complete synthesis and modeling called for in JGOFS has not been specifically planned and it is too important to be left to serendipity.
Modeling activities are critical to the success of JGOFS synthesis. Model representations are the means by which we will test the products of integration among process studies, time series stations, and global surveys. Modeling will be required to fully assimilate the understanding gained through JGOFS in comprehensive analyses of the ocean's role in the global carbon cycle.
The current Mid-Program Strategy augments the effort outlined in the science plan, making specific recommendations for the latter half of the U.S. JGOFS program regarding the role of data synthesis and modeling in current and future field programs, the priority topics on which efforts should be directed, the hierarchy of data synthesis and modeling work required, and the balance of funding between data synthesis and modeling and observations. Investment in comprehensive analyses of the process and time series data sets is a necessary precursor to the larger scale integration of JGOFS findings. The suite of model subcomponents and cadre of scientists who will ensure fulfillment of the JGOFS promise must be developed during the next few years.
2.2 Review of Current Activities
A relevant perspective on the status of synthesis activities is the experience with studies that have been carried out up to the present. It is very clear that too little synthesis and modeling activity was supported for either the NABE pilot project or EqPac. However, because of these experiences we have a clearer view as to how to proceed with the remaining large process studies. Workshops and grants of longer duration are essential, especially when the field campaign schedule is as demanding as it has been for previous processs studies.
As data records for both HOT and BATS approach half a decade, it is also appropriate to review mechanisms in place and assess need for support of synthesis and modeling efforts with these data. Some ancillary science projects have been funded in association with the time series stations, and greater efforts are being taken to encourage other investigators to use JGOFS time series data. It has become very clear from reviews of these data that in many instances where the North Pacific and Bermuda gyres were thought to have little seasonal to interannual variability there is now evidence to the contrary.
As the two global survey components of JGOFS, the CO2 survey and SeaWiFS mission, reach maturity, they too will have requirements for synthesis and modeling activities. As with the process studies, some of these will be self contained, but others will certainly link to the results of process studies and time series stations.
The modeling effort supported directly through the U. S. JGOFS program has been very limited. However, there has been a considerable amount of modeling research relevant to U. S. JGOFS goals funded outside the direct U. S. JGOFS umbrella. The following summary of current U. S. activities is broken down into four major categories beginning with a discussion of modeling research in support of process studies, followed by model studies in support of the time series stations and the global survey, and concluding with a discussion of model development efforts independent of the field programs.
The North Atlantic Bloom Experiment (NABE) was not preceeded by any basin scale model studies. However an eddy resolving diagnostic model was used to provide useful guidance at the time of the expedition through real time simulations of the eddy field in the North Atlantic. This same model is being used to carry out biological simulations. Additional studies have been carried out with a non-eddy resolving model making use of the Fasham, et al.  ecosystem model in a seasonal GCM of the North Atlantic. Results from this coupled model have been compared to satellite data (Sarmiento, et al. ) as well as time series observations at Bermuda Station S and Ocean Weathership Station India (Fasham, et al. ). Plans exist to make use of an updated version of this model for analysis of NABE observations. Additional work is being undertaken to emplace an ecosystem model into the WOCE eddy resolving community model of the North Atlantic. The ongoing studies will play in important role in planning the next North Atlantic study to be done later this decade.
A GCM ecosystem model of the Equatorial Pacific played a major role in planning for the Equatorial Pacific Study (EqPac). Several modeling studies are currently underway to study the physical and meteorological regulation of oceanic primary production in the Equatorial Pacific. The Arabian Sea Study has also had an important circulation model component that was used in planning and will be utilized in interpretation of results. The Southern Ocean process study was recently initiated with a request for modeling proposals by the NSF.
It is important to note that none of the models discussed abeve succeeds in capturing all the important features of the observations. There is much work that remains to be done.
Time Series Stations
A number of groups have been working with the data being obtained from the Bermuda and Hawaii time series stations (BATS and HOTS, respectively). Some studies have focussed on the development of more realistic physical models for these regions, wheras others have focussed on developing improved ecosystem models.
High temporal physical and bio-optical resolution time series have been collected from other sites in the Sargasso Sea ( Dickey et al.,  ) as well as the North Atlantic south of Iceland ( Dickey et al.,  ; Stramska and Dickey  ). These data sets are being used for models at present (e.g., Stramska and Dickey  ) and should be useful to the JGOFS modeling community at-large.
A number of workshops have been organized to bring together scientists who are interested in various aspects of biological/physical modeling at time-series stations. The enthusiastic response to these meetings reflects the broad community interest in time-series studies.
The global survey of carbon is being carried out on WOCE ships primarily with DOE support, as well as on NOAA ships with NOAA support. Numerous scientists within that study have been working on the interpretation of these observations using inverse modeling methods aimed primarily at determining the meridional transport of carbon by the ocean circulation.
The development of models requires an ability to predict the circulation, as well as the formation and remineralization of organic matter. A great deal of synthesis and modeling research has been carried out on the formation, transport, and remineralization of organic matter in association with the process study and time-series stations. Although many papers have been written reporting the observations obtained in the process studies, there is still a major need for synthesis papers that provide an overview of the important results. Such syntheses are essential if the observations are to be utilized by modelers.
2.3 Mid-Program Implementation Strategy
U. S. JGOFS must begin a substantial ramp-up in synthesis activities and the development of models. This is necessary to provide adequate synthesis and modeling support for ongoing and future field programs and time series stations, as well as to meet the goals for grand syntheses and models envisioned at the inception of the program. Doing this will require that the goals of the synthesis and modeling program be defined more specifically. A number of suggestions for this are made below, but more are needed. The Steering Commitee must continue to evaluate progress and identify needs. Resources need to made available to hold regular meetings for synthesizers and modelers and key observationalists to let each other know what they are doing and to make plans for future work. Also, there should be a summer program including students and senior investigators. An early goal of these programs would be to further define the synthesis and modeling goals given below, and to begin addressing specific topics such as the modeling of time series stations, studies of the process study sites, and specific processes of importance such as the cycling of POM and DOM. Such a program would give investigators a chance to interact with each other and to train and motivate a future much needed cadre of scientists.
Following is a first suggestion at defining more specific synthesis and modeling goals within the context of the JGOFS observational program that would improve our understanding and ability to model each of the components of an ocean flux model. The list is given in approximate priority, with ongoing field programs receiving higher priority for early support, and longer term/larger scale synthesis and modeling receiving priority for later support.
The resources that will be required to develop the foregoing program are substantial. Much of these will be provided by funding agencies other than NSF, with a considerable stake in these problem areas by DOE, NASA, and ONR. A considerable amount can also be achieved by close collaboration with the GLOBEC modeling effort. However, it is essential that the NSF funded portion of the U. S. JGOFS program ramp up substantially in order to meet the goals of JGOFS.
We need to have an additional 5 to 10 scientists entrained into modeling and synthesis activities now, and we estimate that by the year 2000 the synthesis and modeling activity necessary to meet the JGOFS goals will require support for at least 10 to 15 scientists, with a comparable effort involved in associated field programs. Directed postdoctoral programs such as the present UCAR program will be of use in providing an influx of newly trained scientists, but it is clear from the response to previous synthesis and modeling initiatives within JGOFS that the capacity to initiate this task on a large scale is already in place today.
We propose specifically that the present NSF modeling support of $260k/yr should be incremented by $500k by FY96 for support of synthesis and modeling. The support of 10 to 15 groups will require a continued ramping up to the level of $3000k-4000k by the year 2000, with most of the increase occuring after the field programs are completed. A comparable level of support will be required for associated field work.
Dickey, T., T. Granata, J. Marra, C. Langdon, J. Wiggert and etc., Seasonal Variability of Bio-optical and Physical Properties in the Sargasso Sea, Journal of Geophysical Research, 98, 865-898, 1993.
Dickey, T., J. Marra, M. Stramska, C. Langdon, T. Granata, R. Weller, A. Plueddemann and J. Yoder, Bio-optical and physical variability in the sub-arctic North Atlantic Ocean during the spring of 1989, J. Geophys. Res., 99, 22,541-22,556, 1994.
Fasham, M. J. R., H. W. Ducklow and S. M. McKelvie, A nitrogen-based model of plankton dynamics in the oceanic mixed layer, Journal of Marine Research, 48, 591-639, 1990.
Fasham, M. J. R., J. L. Sarmiento, R. D. Slater, H. W. Ducklow and R. Williams, Ecosystem behavior at Bermuda Station "S" and OWS "India:" a GCM model and observational analysis, Global Biogeochemical Cycles, 7, 379-416, 1993.
Sarmiento, J. L., R. D. Slater, M. J. R. Fasham, H. W. Ducklow, J. R. Toggweiler and G. T. Evans, A seasonal three-dimensional ecosystem model of nitrogen cycling in the North Atlantic euphotic zone., Global Biogeochemical Cycles, 1993, 417-450, 1993.
Stramska, M. and T. D. Dickey, Modeling phytoplankton dynamics in the northeast Atlantic during the initiation of the spring bloom, Journal of Geophysical Research Letters, 99, 10,241-10,254, 1994.
The U.S. Joint Global Ocean Flux Study Global Survey Implementation Working Group (F.J. Millero, O.B. Brown, J.K. Cochran, G.C. Feldman, J.W. Murray, R.J. Toggweiler and J.A. Yoder) was charged with the task of reviewing the rationale for large scale sampling in JGOFS and discussing the past, present, and future implementation of the Global Survey component of the program. This report discusses the current status of the global survey and recommends ways to improve the program in the future.
3.1 Review of Status of Science Plan
The U.S. JGOFS Long Range Plan (U.S. JGOFS Steering Committee, 1990) gives a detailed rationale for the global survey component of the program. The plan suggests the need for a new global survey with the same spatial coverage as the GEOSECS program in which a new suite of biogeochemical variables are measured. The global survey is an important component of the JGOFS program. It will provide biogeochemical data on the carbon system needed for modeling and provide the link between the surface of the ocean viewed from space and the sedimentary record that views the past. The specific objectives of the large scale program are:
The implementation of this plan was to be achieved by:
3.2 Review of Current Activities
It was recognized early in the program of the need for a major global survey of the oceanic carbon chemistry (CCCO, 1988). This led to the agreement by JGOFS and WOCE to coordinate the measurement of CO2 on the WOCE WHP cruises. Two berths were made available to make carbonate measurements. The measurements of TCO2 (total carbonate), TA (total alkalinity), and pCO2 (partial pressure of carbon dioxide) were to be made, respectively to 1 mol/kg, 1 eq/kg, and 1 atm. This accuracy is presently achievable. Intercalibration and intercomparison exercises have been initiated for the components of the carbonate system by the DOE science group under the direction of Andrew Dickson (Scripps). This group has also written detailed protocols for the measurement of the CO2 parameters. As part of this work, TCO2 and TA standards are now available. This will insure that the measurements made by various groups will satisfy the requirements of the JGOFS program. This global carbon dioxide survey is the primary goal of the global survey and should be strongly pushed.
An agreement was reached that when possible a third berth would be available to JGOFS scientists who would make measurements of the underwater optical field and phytoplankton pigments distribution. The implementation of the optics and pigment part of the global survey has been considered by the U.S. JGOFS Optics Task Team (Marra, 1991). The goal of this work is to be able to improve the algorithms used for computing chlorophyll from satellite ocean color. It is important to get as much global coverage as possible to develop a world-wide pigment data base.
Much of the above satisfies the JGOFS contribution to the global survey. Notably lacking in the present program is the global array of sediment traps and benthic measurements. This is due to the lower priority of these studies and the large scale costs of carrying out these activities on a global scale. The activities have been carried out as part of the process studies and are not completely lacking in the JGOFS program. More effort should be made in making continuous pCO2 measurements on all the JGOFS and WOCE cruises and ships of opportunity.
3.3 Detailed Implementation Strategy
3.3.1 Present Global Surveys (Near Term)
To satisfy the important goals of the present JGOFS global survey program we recommend:
3.3.2 Future Survey Programs (Medium Term)
The implementation task group also considered the possibility of carrying out more limited surveys in future years. It was realized that the funds and scientific interest in carrying out another large scale global survey was not in the cards. Further measurements on a few of the long survey lines may be of interest every five years, but more limited surveys may be needed to solve some key questions that are presently important or may come about as a result of process studies and the initial results of the global survey and the process studies. Some of the science questions that can be addressed by such studies considered by the task team are given below.
Seasonal Survey of pCO2 in the North Atlantic: There presently is a growing contro- versy over the size of the oceanic sink for CO2 (Tans et al., 1990). Ocean models suggest that the sink must be 2 Gt/y with 1.2 Gt/y in the southern and 0.8 Gt/y in the northern hemispheres. These models are based on the known geographical distribution of fossil fuel burning and the time constant for gas exchange between the hemispheres. They show that the southern hemisphere ocean has no net uptake or loss to the atmosphere. Thus, the northern hemisphere must be absorbing the entire 2 Gt/y. Present estimates, however, are only 1 Gt/y. It is important to assess the accuracy of the lower sink estimates based on oceanic data. The recent JGOFS process studies in the North Atlantic have shown that pCO2 is extremely patchy in the spring and summer. Strong correlations were found between chlorophyll and pCO2 as well as latitudinal gradients (Turner et al., 1989). There is thus an urgent requirement to document more accurately the seasonal cycle of pCO2 in the North Atlantic and Pacific and, if possible, the Southern Ocean. At present seasonal surveys of the North Atlantic would be the easiest to achieve. The minimum requirements would be underway measurements of pCO2 and TCO2 along the cruise track, backed by measurements of chlorophyll. Measurements of primary productivity, optical properties and plant pigments would also be useful. These studies could also supply the data needed to ground truth the SeaWiFS satellite color data. These measurements were regarded as a high priority for JGOFS (SCOR, 1990) and can be carried out as a series of survey cruises. We recommend that every effort be made to develop a U.S. JGOFS component for this program as soon as possible.
Thermocline Ventilation in Subtropical Gyres: A significant problem exists with regard to the carbon balance in the North Atlantic subtropical gyre. Several different approaches have been used to estimate new production. Oxygen-based remineralization rates utilizing helium/tritium and 228Ra lead to values ranging from 2.5 to 8.5 mol C m-1 y-1 (Riley, 1951; Jenkins, 1980; 1987; Sarmiento et al., 1990). Estimates based on mixed layer oxygen production range from 3.0 to 5.6 mol C m-1 y-1 (Spitzer and Jenkins, 1988; Musgrave et al., 1988). All of these estimates are higher than expected based on annual values of primary productivity and conventional ideas about food web structure and nutrient recycling. Estimates of new production based on vertical nitrate supply (Jenkins, 1988) and particulate flux measurements (Altabet, 1989) are about an order of magnitude lower (0.33 to 0.6 mol C m-1 y-1).
One hypothesis that may resolve this discrepancy is that oxygen consumption and nitrogen remineralization rates are greater than the vertical flux of local new production because of respiration of dissolved organic matter of remote origin transported into the thermocline by ventilation. There is a need to study the mechanism and processes controlling the horizontal and vertical transport of DOC/DON and chemical tracers of respiration from the surface region of density outcrops into the thermocline. There have been few studies of DOC in the thermocline region. In all cases a good correlation exists between DOC and AOU, although the slope of the relationships vary and their origin is unclear.
Another important reason for studying this region is that ventilation of the thermocline is one of the main short time scale pathways for the removal of fossil fuel CO2 from the atmosphere (e.g., Bradshaw and Brewer, 1988; Brewer et al., 1989). As atmospheric CO2 increases, so does the CO2 content of the water subducted. A detailed study of the source region is required to understand how the CO2 signature of the subducted water is determined.
Thermocline ventilation occurs primarily as a pulse produced during the winter cooling. The composition of the source waters supplying the ventilation needs to be determined to set the initial boundary values. This study will help define how subsurface ocean water acquires its preformed nutrient signatures.
This component of the Global Survey should consist of seasonal sections from the high latitude isopycnal outcrop regions to the center of the subtropical gyre. Sampling should cover the water column through the deepest density surface that outcrops (about = 27.4). A complete set of chemical tracers of respiration and ventilation rates should be measured and chemical and biological studies of the outcrop region should be conducted. It could be conducted in either the North Atlantic or Pacific, however, the larger historical data base in the North Atlantic makes it a more logical choice.
Measurements of Pigments and Optics: One of the key JGOFS strategies is to use satellite ocean color measurements to help determine the mean end fluctuating components of ocean basin primary production. To help accomplish this objective, global surveys can make two im- portant contributions. First, surveys will provide a large data base of near surface chlorophyll a (and other pigments) concentrations to compare with estimates derived from satellite sensors, either from concurrent observations or in a climatological sense. These observations will be particularly valuable if spectral reflectance measurements are made at the same time as the pigment measurements. Secondly, surveys will determine how well euphotic zone Chl a (depth-integrated) can be estimated from near surface measurements. The latter is particularly important, since Chl a is not always uniformly distributed in the euphotic zone.
The global survey of Chl a and optical measurements will be useful only if the mea- surements are made using the proper techniques and if the results are expeditiously compared with satellite observations. These requirements mean that:
No requirements have been set for horizontal station spacing. With respect to the measurements described here, the role of the survey is to define large scale gradients in Chl a and its relation to spectral reflectance. Thus, the sampling plan presently calls for samples to be collected once per day during WOCE WHP cruises, and this may provide an adequate data base. However, there are major parts of the global ocean and times of the year where we anticipate problems in using satellite ocean color data to estimate phytoplankton biomass, productivity and other in-water constituents and processes. These areas may need to be revisited during specific seasons and sampled more extensively than possible by WHP.
Measurements of Sediment and Benthic Parameters: The ultimate fate of particulate organic carbon which escapes the surface waters and sinks to depth lies in processes happening near the sediment-water interface or in bottom sediments. Studies of these benthic processes are required to determine the fluxes of carbon and nutrients to the sediments and back to the bottom water. Moreover, studies of the controls on organic carbon preservation, as well as opal and calcium carbonate, in the marine sedimentary record are necessary for the reconstruction of paleoproductivity. The magnitude of benthic fluxes varies from place to place, and in margin areas (shelf and slope) the intensity of carbon cycling is often greater than in the deep sea.
In the context of JGOFS, benthic studies have both process and survey components. The aim of the survey studies is to map the spatial and temporal variability of carbon fluxes in the ocean. Although a large scale benthic survey is now an unlikely component of JGOFS, significant information on the spatial variability in benthic carbon fluxes can be gained through incorporation of a survey component in process studies. The strategy favored by the JGOFS Benthic Process Task Team is to make flux measurements along transects through areas such as those of equatorial upwelling, eastern and western boundary currents, continental margins and shelves, polar seas and central gyres. Many of these areas have been targeted for process studies, and a benthic survey component can be added by making sure that each process study site has a transect of benthic stations through it. The priority for such transects should be:
Larger scale mapping of benthic carbon (and perhaps nutrient) fluxes may be facilitated by measurements of proxy indicators of flux. For example, Pb-210 removal from the ocean water column has been correlated with carbon flux in sediment traps (Moore and Dymond, 1988), and measurements of excess Pb-210 inventories in sediment cores may reflect long term average carbon fluxes to the site (Cochran et al., 1990). Thus collections of box cores on JGOFS and related cruises could expand the benthic survey data base.
In order to constrain the near-bottom cycling of carbon, both flux measurements and rates of processes must be measured. Flux measurements include: 1) the sinking particle flux (measured by particle traps, filtration, optical or isotopic methods), 2) the permanent burial flux due to long term sediment accumulation, and 3) solute fluxes across the sediment water interface. Important rates of processes which must also be measured include: 1) the rate of organic carbon oxidation, 2) the rate of biological mixing of sediments (by particle mixing and burrow irrigation) and 3) the rate of physical transport processes which affect exchange between sediment and bottom water. A JGOFS Benthic Survey must then include components dealing with benthic biology, microbial ecology, pore water geochemistry, benthic flux measurements, sediment coring, and particle trap deployment and recovery.
3.4 Resources Necessary for the Future Limited Surveys
The resources necessary to carry out the more limited surveys or process studies are estimated to be in the $1 to $2M range. This estimate is based on the involvement of 3 to 5 scientists and estimated shiptime of 30 to 60 days. Since most of the surveys listed above can also be considered as mini-process studies, we recommend that they be funded as outlined in the prospectus approved by the JGOFS Steering Committee.
4.1 Review of Status of Science Plan
The U.S. JGOFS Science Plan (U.S. JGOFS Steering Committee, 1990) provides a detailed rationale for the time-series component of the program. The plan suggests that time-series observations extending over many years are the only strategy by which the longer term cycles and trends of the ocean can be observed and understood. Logistical requirements of time-series measurements are a dominant concern and therefore island stations assume a particular importance.
The objectives of the time-series studies within JGOFS are: 1) to observe and interpret the annual and interannual variability in the biology and chemistry of the mixed layer and euphotic zone as forced by physical processes, 2) to observe and interpret the annual and interannual variability in the rates of particle flux and the apparent rates of particle remineralization over the entire water column, 3) to understand the interrelationships between the biological, chemical and physical processes involved in (1) and (2) above, and 4) to provide data on global trends of selected oceanic properties over seasonal and interannual time scales.
In addition, time-series stations are optimal sites for:
4.2 Components of the Time-series Program
The implementation of the time-series part of the U.S. JGOFS Science Plan will be coordinated with other international programs within JGOFS. The main components of a time-series program include:
4.3 Review of Current Activities
At present there are two manned time-series stations as part of the U.S. JGOFS program. These are located near the islands of Bermuda and Hawaii. Both have conducted monthly cruises since October, 1988. The island locations and histories of the institutions responsible for the measurements make logistics easier than in other areas. Both of the existing time-series stations are located in oligotrophic gyres of the Atlantic and Pacific oceans, with the Bermuda station showing strong seasonal patterns of mixing and production.
4.3.1 The Bermuda Atlantic Time-series Station (BATS)
BATS was established in early 1988. The station is located at the Ocean Flux Program (OFP) site (3150N, 6410W) 80 km southeast of Bermuda with a water depth of 4,800m. Monthly hydrographic cruises commenced in October, 1988. The site is near the location of Werner Deuser's (WHOI) mooring site for deep sediment traps, a continuing record of deep sinking fluxes that began in 1978. Hydrostation S lies 22 km southeast of Bermuda and the 40 year time-series record of biweekly hydrographic sampling is continuing at this station. Thus, BATS continues and builds upon a long tradition of time-series research in this area. To date over 75 cruises have been carried out. In addition to the major monthly cruises, sampling frequency has increased during spring with a set of short cruises to document the yearly over-turn and bloom period.
4.3.2 The Hawaii Ocean Time-series (HOT)
The HOT program is a multi-investigator, interdisciplinary research program that has successfully established and maintained a deep, open ocean hydrostation for the purpose of observing and interpreting oceanic variability. The HOT program has two major components: JGOFS and WOCE. This cooperative arrangement has resulted in a close collaboration between the JGOFS and WOCE program scientists at the University of Hawaii and will undoubtedly yield a higher quality data base than either of the individual groups could have assembled alone.
In October 1988, a permanent site was established at a location referred to as Station ALOHA (A Long-term Oligotrophic Habitat Assessment). The station is approximately 100 km north of Oahu at 2245N, 15800W, and is near a TOPEX/Poseidon satellite crossover point. It is 50 kilometers away from the steep topography associated with the Hawaiian Ridge. The water depth is 4,750 m, the seafloor is without relief, and the sediments are predominantly composed of pelagic red clay. Station KAHE, located off Kahe Point at the 1,000 m isobath is also routinely occupied during monthly cruise operations. Between October 1988 and the end of 1994, fifty research cruises were conducted to Station ALOHA.
4.3.3 Measurement Parameters
The following parameters are routinely measured at the BATS and HOT sites:
The results from both stations are sent to the U.S. JGOFS Planning Office at the Woods Hole Oceanographic Institution and then forwarded to the U.S. NODC in Washington DC., where they are available to the community as a whole.
4.3.4 Other Activities
Other activities within the U.S. JGOFS effort include method development for time-series measurements, interaction with international JGOFS programs involving standards, reference materials and development of measurement protocols. Part of this component could include training and advice for other international time-series programs.
4.4 Detailed Implementation Strategy
4.4.1 Near Term
The location of future time-series stations as part of the U.S. JGOFS effort must be determined by the overall scientific goals of the U.S. JGOFS program. The design of each time-series sampling program must be determined by the nature of the environment, the scientific questions involved and the major logistical considerations. Therefore the manned-ship-cruise effort presently at Bermuda and Hawaii needs to be continued and needs to be supplemented by new automated time-series technologies (e.g., moorings, automated underwater vehicles) as they emerge to provide a linkage between the different approaches. Future time-series stations would use the appropriate combination of ships, moorings or AUV's determined by the scientific goals. These two existing sites are critical as test beds for existing and emerging technologies for time-series measurements world-wide. They are also essential for training and other educational activities within the JGOFS program as a whole. Many of the areas of interest to JGOFS are in logistically difficult areas, therefore a commitment to technological development is essential.
220.127.116.11 Future Time-series Sites
Selection of future time-series sites will be based upon the following criteria:
Most resources are presently available for the two existing time-series sites to carry out the work detailed above. Additional resources are required to fund the core measurement work above until 1998, with the addition of bio-optical, acoustical, geochemical and physical mooring-remote sensor development at both sites. These research activities require approximately $1M per annum per site, excluding 60-75 days of shiptime. Additional resources would be required to expand the scope of the research or to automate the existing measurement programs. For example, the addition of a physical/bio-optical mooring would require a supplement of at least $400K per site with continuing costs of approximately $150K per year.
4.4.2 Medium Term (0--2 years)
Resources will be required for various time-series aspects of the process studies planned or in the planning stages. These resources will be required within the design of each process study and will be listed as part of the individual process study. As the long term plan for reoccupation of process study sites becomes more firm, it will be imperative that the time-series stations be established to provide a link between these periods of major occupations.
4.4.3 Long Term (0--5 years) Automated In Situ Instrumentation for JGOFS Time-series Observations
Automated in situ instrumentation is needed for time-series observations of bio- geochemical, bio-optical, acoustical and physical variables at present and future JGOFS time-series sites for several important reasons (see review by Dickey, 1991; Dickey et al., 1993).
18.104.22.168 Sensor Development
In order to detect physical climate change, relatively simple measurements of temperature are crucial. In terms of biogeochemical changes, variables such as pCO2, total CO2, alkalinity, dissolved oxygen, water clarity, pigment biomass, and phytoplankton productivity are the master variables. The unambiguous interpretation of measurements used to determine these quantities remains a challenge, however, considerable progress in making high-resolution, long-term bio-optical, biogeochemical and acoustical measurements has been made and rapid advancements in sensor and system development seem likely. Therefore, automated sampling at time-series sites is not only important, but technologically feasible. This will require a commitment to testing and use of established sensors as well as improvement and development of new sensors.
22.214.171.124 Site Selection
Global scale changes cannot be determined from a limited number of time-series sites. However, changes at these sites can be used to monitor long-term trends and indicators of significant changes in oceanic biogeochemical and bio-optical variables, just as the measurements at Mauna Loa have provided compelling evidence of atmospheric CO2 concentration increases. Therefore it is intended to take advantage of the core data measurements at the Bermuda and Hawaii sites to test some of the present and future technologies and add to the temporal data base.
In addition, remote sensing of ocean color and the derivation of upper ocean pigment biomass and primary productivity on regional and global scales will be done with SeaWiFS. The requisite algorithms rely on in situ observations of bio-optical variables. Therefore, inconsistencies between satellite and in situ sensors in temporal and spatial sampling scales must be interpreted and corrections derived at these stations. Additionally, satellite-derived ocean color and temperature measurements are often obviated by cloud or water vapor conditions. Further, the understanding and interpretation of fundamental measures such as fluorescence remain problematic. Therefore, intensive and extensive shipboard sampling at mooring sites will be important.
126.96.36.199 Data Acquisition
One of the advantages of automated sampling is that data collected from such systems, in principle, can be transmitted in near real-time to shore-based laboratories around the world. The ARGOS satellite communication system is presently used by programs such as the Tropical Ocean Global Atmosphere (TOGA) program to distribute meteorological and physical data in near real-time. The near real-time capability is useful for continuous monitoring, planning sampling strategy, and for insuring data retrieval in the event of instrumentation loss or major malfunction in data recording. An advanced version (greater data transmission capabilities, especially bandwidth and volume) of ARGOS will be needed for the large number of variables collected at high data rates. Presently, near surface instruments are easily linked to such communication systems and technological advances are being made in transmitting data from depth acoustically (e.g. Dickey et al., 1993).
188.8.131.52 Description of Platforms
The three primary modes of collecting in situ data from automated systems will be from moorings, tethered vehicles and AUV's. Several successful experiments have now been done using moored bio-optical, physical, and geochemical sensors in the open and coastal ocean (e.g., review by Dickey, 1991). A detailed discussion is presented below as these platforms will be essential in the long term for JGOFS as well as for systems such as the Global Ocean Observing System (GOOS).
These devices are important for the JGOFS time-series program as they may be used:
Development of interdisciplinary moored instrumentation systems has been driven in part by the need to increase the time domain of bio-optical, biogeochemical, and acoustical sampling. The selection of appropriate sensors and inherent constraints such as power consumption, data storage, and biofouling are of special concern for this method of deployment. The potential of obtaining moored bio-optical data has only begun to be realized. Yet data have been collected in several regions of the world ocean (e.g., Sargasso Sea, the coasts of California and New York, Equatorial Pacific, and Iceland) from moorings (see review by Dickey, 1991; Dickey et al. 1993).
Some of the moored sensors include: thermisters, conductivity sensors, vector measuring current meters, strobe fluorometers, natural fluorometers (683 nm upwelling radiance), photosynthetic available radiation (PAR) sensors, beam transmissometer (660 nm), dissolved oxygen sensors, spectral downwelling irradiance sensors (410, 441, 488, 520 and 560 nm), and spectral upwelling radiance sensors for the same wavelengths. Data are typically recorded every 1-4 min. Because of the high temporal resolution, it is possible to do spectral analysis of bio-optical as well as physical data in the open ocean. The processes contributing to variability shown in resulting spectra include diel cycles of phytoplankton, tides, inertial currents generated by passing weather systems and wind events, and internal gravity waves. Variability in stimulated fluorescence and beam attenuation coefficient are related to phytoplankton biomass. Recently, estimation of primary production using models and data obtained from time-series bio-optical measurements has become possible. Some of the methods which can be used to estimate primary production using mooring data have been presented by Kiefer and Mitchell, (1983), Emerson, (1987), Siegel et al. (1989), Kiefer et al. (1989), Dickey (1991), Marra et al. (1991), and Stramska and Dickey (1993).
184.108.40.206 Tethered Vehicles
Remotely Operated Vehicles (ROVs) are an emerging technology that show great promise for addressing specific research questions related to JGOFS goals. These vehicles are tethered to a surface platform, usually a research vessel and are controlled from the surface through the tether. The surface connection frees these vehicles from many power and data transmission constraints. They can transmit live video images and other wide-bandwidth data to the surface in real time. They can have sophisticated sampling and manipulation equipment onboard and controlled from the surface. Conversely, they are constrained by the length and hydrodynamics of the tether system to measurements near the surface platform, although some of these constraints will lessen as new tether management systems become available. The most apparent uses for these vehicles in the JGOFS context is in conducting specific, process-oriented experiments on ocean biogeochemistry. They allow direct observations of the many organisms that mediate midwater and benthic organic transformations. They allow the quantitative enumeration, collection and incubation of marine snow particles, the dominant type of sinking particles in many parts of the ocean. They are a direct extension of the human eye and laboratory in to the deep sea and are more cost-effective than submersibles that actually carry humans to depth.
220.127.116.11 Autonomous Underwater Vehicles (AUV's)
Exploration of the subsurface ocean has for the most part been done using ships, submarines, submersibles, or remotely operated vehicles and thus required human resources. These methods are costly and require considerable manpower. Thus, there is renewed interest in the development of autonomous underwater vehicles (AUV's) which could be used for regional and global sampling. AUV's can be thought of as ``robotic submarines. A generic AUV may be defined to be a ``free-swimming,'' untethered vehicle with its own power supply, propulsion unit, computer intelligence systems for decision making, navigation, etc., communication links and telemetry, and system and scientific sensors and discrete water samplers. Various institutions have been involved in AUV development over the course of the past 30 years.
The current enthusiasm for AUV's is spurred in part by technological advances in miniaturized computers and artificial intelligence. In addition, a broader suite of oceanographic sensors and water samplers is now available. Some of the necessary electronics, computer control, and scientific sensor capabilities are being utilized for moored instrumentation used for bio-optical and geochemical as well as physical observations (sampling domain of minutes to months).
18.104.22.168 Summary of Automated Instrumentation Needs for JGOFS
Many of the present uncertainties in the estimation of carbon budgets are caused by 1) undersampling (aliasing), particularly in time and space (Dickey, 1992; Wiggert et al. 1993), 2) uncertainties and limitations in existing measurement techniques involving primary production and sediment trap methodologies (Jahnke, 1990), and 3) the lack of concurrent physical, bio-optical, and biogeochemical data (Dickey, 1991; Dickey et al. 1993).
Observations from moorings, ships, and satellites all have sampling advantages and disadvantages. It is anticipated that the moored, tethered and AUV observations at time-series sites will be most useful in reducing many of the present ambiguities and provide new insights into the complicated carbon cycle within the framework of JGOFS. Therefore resources for such technology will be part of the overall JGOFS budget.
All of these new technologies will feed into a new integrated data assimilation system Global Ocean Observing System (GOOS) modeled after the global meteorological stations.
22.214.171.124 Resources Required for Automated Instrumentation Needs
It is unreasonable to assume that JGOFS will bear the burden of full funding for moorings, tethered submersibles or AUV prototype design and field testing. Other federally sponsored research programs, for example the ongoing $10M Office of Naval Research AUV project, will provide invaluable engineering and feasibility data. A fully instrumented JGOFS-AUV (e.g., Ocean Voyager II) is expected to cost $250K and have annual operating costs of approximately $150-200K.
Deep-sea physical/bio-optical moorings have been successfully deployed in numerous locations worldwide. Construction costs vary considerably depending upon configuration and, especially, instrumentation, ranging from $200K to $2M.
Because of their inherently high rates of data acquisition, continuously recording instruments require an additional investment in Data Management at a level of approximately $100K per site.
5.1 Review of the Status of the Science Plan
The US JGOFS Long Range Plan (US JGOFS, 1990) laid out the scientific justification for process studies. The overall goal of the process study component of JGOFS is to provide insight into key biogeochemical ocean processes, leading to mechanistic understanding which can be expressed in equations and coded in a hierarchical selection of models. A detailed inventory of process study objectives and elements is given in the International JGOFS Science Plan (SCOR, 1990). Biogeochemical processes themselves are generic and common to all the major biogeochemical provinces of the global ocean, but the relative importance, and regulation of processes differs among basins and provinces. In the Long Range Plan, 13 process studies in 11 oceanic provinces were proposed. Following the completion and assessment of the Pilot Study in 1989, and a further assessment of resources available for JGOFS, the list of 13 major studies has been reduced to a group of 4 high priority process studies. Provision has also been made for an unspecified number of smaller, focused, "miniprocess" studies. The four major regional process studies are described following a brief description of the Pilot Study.
5.2 Description of a Process Study
Process Studies fill an observational gap not covered explicitly addressed by Large Scale Surveys and Time Series operations. They are conceived to address fundamental problems of carbon and associated fluxes in strategically-chosen ocean basins on scales at once more focused in time than surveys and wider ranging spatially than time series stations. The scientific designs of different studies will take somewhat different forms depending on the specific objectives and logistic demands in each region, but the generic model of a centrally-coordinated, international collaborative program of observations and synthesis will be followed in each case.
The model for Process Studies in JGOFS is the Pilot Study, or North Atlantic Bloom Experiment (NABE), which took place in 1989-91. NABE was coordinated by the JGOFS Scientific Steering Committee through a Pilot Study Coordinating Committee made up of the national coordinators of the participating nations. The study itself was international, multidisciplinary and broadly collaborative. Research vessels from five nations (Canada, The Federal Republic of Germany, The Netherlands, The United Kingdom and The United States), a NASA aircraft and satellites for remote sensing, and moorings were deployed for this study of the spring phytoplankton bloom (Ducklow and Harris, 1992). In the USA, NABE consisted essentially of 17 projects with 25 principal investigators, at a cost of less than $10M. The results of NABE were reported at a Scientific Symposium held at the National Academy of Sciences in November 1990, and a volume of scientific papers was published in 1992 (Ducklow and Harris, 1992).
The first full scale process study was the Equatorial Pacific Process Study (EqPac), which completed its fieldwork in early 1993. Its composition, size and cost are detailed below in Section 5.6.1.
5.3 Guidance and Planning
Since the initiation of the NABE Pilot Study, JGOFS has set up a number of mechanisms to ensure efficient and proper planning, execution and synthesis of process studies. The various groups and activities are described briefly below, and the individual elements for each study are given in the sections on each study.
The US JGOFS SSC has ultimate responsibility for the design, implementation, execution and synthesis of each Process Study. The composition (PI's) and size (cost) of the studies are determined by the review and budget process in the funding agencies. While most of the tactical and scientific decisions regarding the operational phases of the studies will be made by the planning and coordinating groups and even by individual scientists, the SSC, through overall guidance of the planning process should decide the priority questions, form planning and coordinating committees, coordinate observational elements and set the timetables for each study. The SSC has taken several important steps toward implementing the process studies: i) initiated the planning process for the Equatorial Pacific, Arabian Sea, Southern Ocean and North Atlantic studies; and ii) requested informal proposals for additional process studies in different ocean provinces.
Following the precedent established during the Pilot Study, Regional Planning Groups or Process Study Coordinating Committees have been formed to define the scientific rationale and plan and guide each study. Each groups is composed of scientists with particular expertise in the geographic region, chosen to provide disciplinary balance, with a Chair or co-Chairs recognized by the SSC. The composition of each of the planning groups is listed in the appropriate section below. The planning groups are responsible, among other charges, for convening a series of planning meetings as defined below.
The Leaders of the Regional Planning Groups are members of the extended Executive Committee of US JGOFS. The "Exec-plus" is be responsible for coordinating and guiding the process studies, establishing a liaison between the SSC and the regional groups, and among the groups, and organizing synthesis and modeling activities for the process study component of JGOFS.
Much of the planning activity for Process Studies is carried out in a series of meetings following the Pilot Study model. The time frame and sequence of the meetings and the implementation of the field study defines a time line for implementation of each process study which lasts approximately 4-6 years. Time lines for each process study are included in the individual sections below.
Timeline for implementation of a major process study.
5.4 Resource Spectrum
Process studies require a large and diverse array of observing systems and analytical resources to meet their goals. The major types of resources are listed here, and some of the details of their deployment are given in the following sections on the individual studies. Process studies are neither as extensive in time as time series, nor in space as surveys. Observational resources need to be chosen to facilitate extrapolation and generalization of process study results. Mooring data can place the discrete observations from individual cruises in a temporal context. Aircraft observations will do the same for the spatial context. Satellite data, after being carefully compared to the multidisciplinary cruise data and mooring data, will be used to extrapolate to interannual time-scales and basin scale space scales. All of these data combined with the models gives us a synthesis of present-day response to climate variability that can be used to study past and future characteristics of the carbon cycle of the basin, and to apply the insight to other regions of the world.
Research vessels. Cruise data will provide the basis for gaining a mechanistic understanding of how various interdependent processes control the carbon and nitrogen cycles in study regions. JGOFS process studies are focused primarily on open ocean problems. Following the Pilot Study model, a minimum of ca. 500 days of shiptime is required on ca. 5 vessels per year of internationally-coordinated field study. The US JGOFS Program alone requires at least one dedicated large research vessel for a period of about one year. To accommodate the scientists and technicians required to address the Core Measurements (see below), large vessels with 40--50 day endurance capable of housing 20--40 scientists are needed. Smaller (coastal) research vessels may also be needed for ancillary investigations, mooring deployment/recovery, etc.
Satellites. In addition to their primary role in data collection for the Global Synthesis (Chapter 3), remote sensing satellites are needed for real-time guidance of sampling operations and interpretation of shipboard operations. Satellite data, after careful comparison with multidisciplinary cruise data and mooring data, will be used to extrapolate to interannual time scales. Thus provision of ground stations or shipboard receiving and data processing capabilities during field operations is essential for JGOFS. The satellite-borne sensors of greatest utility are ocean color instruments, sea surface temperature radiometers and altimeters (e.g., Robinson et al., 1991).
Aircraft. Satellite observations are subject to interference from clouds. Remote sensing aircraft equipped with LIDAR's and radiometers for SST and ocean color provide high resolution viewing of process study areas and are less vulnerable to cloud cover interference. The NASA P-3 equipped with LIDAR was used in NABE and its successor was flown in EQPAC.
Moorings. Ships can make observations of limited temporal continuity and satellites only view the ocean surface. For more comprehensive temporal coverage, depth-dependent observations and relative independence from weather, a variety of moorings have been and will be used in JGOFS. Moorings will provide data on the variation of properties both during process measurements and at times when process measurements are not being made. The daily process observations can be extrapolated to wide areas and to monthly time scales using the mooring data. These include LOTUS-type and other upper ocean physical/meteorological moorings and bio-optical moorings (Dickey, 1991) in addition to deep ocean sediment trap moorings (Deuser, 1986). Chemical moorings capable of sensing dissolved gases and nutrients are under development and will be used in later process studies.
5.5 Core Measurements
One of the most important aspects of the JGOFS observational strategy is the development of protocols for a list of Core Measurements. A preliminary version of these protocols was developed for the Pilot Study (JGOFS Report 6). More detailed sets of protocol descriptions were developed for the Time Series sites (described in the time series data reports and at their Web sites). A record of the methods (core and additional) employed in EQPAC is also available (JGOFS, 1995). A comprehensive set of protocols for the International JGOFS Program, written in a uniform format, has been published (JGOFS, 1995). The list of core measurements was developed in consultation with modelers and addresses the variables and rate processes required to provide adequate descriptions of biogeochemical processes and their hydrographic background for development of biogeochemical process models. An important goal of JGOFS is to build the capability to perform each measurement to JGOFS standards following the accepted protocol, on each process study cruise. The list of JGOFS Core Measurements includes the following parameters which should be measured in most phases of each process study:
The results of the process studies form a large and diverse array of products, including data sets generated by individual PI's and technical service units, research papers, and new models. Proper synthesis of these products requires a planned sequence of activities to ensure optimal use by the program and future scientists. Process study synthesis begins with interaction between the process study coordinators, PI's and data managers to facilitate data submission and access. Several scientific meetings and at least one large data workshop are usually needed to familiarize project PI's with the initial and individual results of component projects in a process study. Other smaller, more focused workshops devoted to special topics may also be required. Following these data presentations, a large synthesis workshop is convened to promote interaction among PI's and initiation of collaborative and interdisciplinary interpretation of data. The data and synthesis workshops for EQPAC were held 1 and 2 years following the completion of the fieldwork, and each lasted for 5-10 days and a university or conference center.
5.7 The Process Studies
5.7.1 Equatorial Pacific Process Study (EQPAC)
Time Frame: (Field Studies): 1991-1993
Planning Meetings, Reports and Workshops:
5.7.2 The Arabian Sea Process Study
The Arabian Sea Process Study is currently being implemented. Proposals were submitted to NSF for review in February, 1993, and decisions were made approximately one year later. A more detailed description of the Arabian Sea Process Study is given in the U.S. JGOFS Arabian Sea Implementation Plan
(Smith et al. , 1992).
Rationale: At the present time, it is unclear whether the northwestern Indian Ocean (Arabian Sea) is a sink for atmospheric carbon dioxide via its high rates of primary productivity and large concentrations of sedimentary carbon, or a source via outgassing of carbon dioxide brought to the surface during upwelling. The unique properties of the Arabian Sea can be used to expand our general understanding of the carbon cycle, productivity, and vertical flux of particulate material and biogeochemical transformations in the sea. Its principal unique feature is the regular oscillation of high rates of primary production and generally oligotrophic conditions under relatively constant levels of illumination. The oscillations in productivity and biomass that in high latitudes are forced by temporal variations in solar irradiation are here of a similar magnitude, but are forced by monsoonal atmospheric conditions which, via surface pressure fields and baroclinic adjustments, affect mixed-layer development and nutrient supply. The Arabian Sea experiences extremes in atmospheric forcing that lead to the greatest seasonal variability observed in any ocean basin. The wide range of climatic variability in the Arabian Sea makes it an excellent place in the present-day ocean to look clearly at past climates and possible future climates.
Time Frame: late 1994 - early 1996.
Objectives: The objectives have been broadly summarized in the U.S. JGOFS Planning Report Number 13 (Smith et al. , 1991). In that report, each objective is broken down into specific questions for the general categories of primary productivity and carbon/nitrogen cycling, heterotrophic processes, water column geochemistry, and benthic fluxes/paleoceanography. The questions are:
Scope of the Study: The U.S. JGOFS Process Study in the Arabian Sea will take place from September 1994 through January 1996. Other U.S. research programs in the region, specifically U.S. WOCE and the U.S. Office of Naval Research's (ONR's) Forced Upper Ocean Dynamics Program, will be conducted in parallel with U.S. JGOFS and coordinated with JGOFS. The U.S. JGOFS investigation alone will require 10 months of ship-time in 1994-1996. The schedule follows. Figure 2 shows the locations of U.S. JGOFS moorings and stations for process observations. A cruise track has been devised that includes six long stations, nine intermediate stations, and twelve hydrographic stations (Figure 2).
During pelagic process cruises, each of six long sampling sites will be occupied for a period of two days each for the purpose of establishing diel and variability in all relevant processes. These six sites are located in the area of very positive wind stress curl (2), in the area of very negative wind stress curl (1), in slightly positive curl (1), in slightly negative curl (1), and in the suboxic area near India. During benthic/paleoceanographic cruises, coring and other sampling are focused on the sites where sediment traps are moored (Figure 2) on the continental shelf and on the continental slope.
Mooring instrumentation for biological and chemical time-series will be emphasized in the Arabian Sea Expedition. Observations that will be made from moorings include temperature, salinity, scalar irradiance, particle concentration, chlorophyll, sedimentation, meteorology, and zooplankton biomass.
It is anticipated that the scatterometer, AVHRR, and altimeter satellites will be fully operational during all of the investigation of the Arabian Sea. SeaWiFS may be operational during the final months of the expedition. Aircraft overflights for surface pigments will be done during July, a month in which the historical CZCS records indicate haze or dust often rendered the CZCS records useless. Attempting to quantify the haze and dust of the region by satellite should be a high priority investigation.
Models for the region exist at Florida State University, Nova University, Princeton University and the Naval Research Laboratory. Efforts to incorporate U.S. JGOFS biological and chemical variables into these models were made prior to 1994,with the result that the cruise track was modified on the basis of model results. Development of these models for the Arabian Sea should continue, as a guide to planning field work, and in the future to synthesize the large data base anticipated from the ship and mooring observation programs.
Finally, knowledge of meteorological forcing is essential to the successful completion of the investigation. Meteorological instrumentation will be included in the mooring program and all research vessels intending to participate in the investigation must be equipped with complete and up-to-date meteorological capability.
Observations: This suite of observations is considered the fundamental data set that should be acquired during pelagic process cruises in the Arabian Sea.
Meteorological Observations Hydrographic Observations (depth-resolved) wind speed conductivity wind direction temperature humidity oxygen sea-surface temperature nutrients air temperature pigments barometric pressure fluorescence precipitation POC, PN and DOC solar radiation CO2 system properties longwave radiation particles (transmissometry) dust fall scalar irradiance Pelagic Standing Stocks Pelagic Productivity and Grazing
phytoplankton carbon mesozooplankton nitrogen microzooplankton oxygen bacteria mesoplankton and microplankton
On benthic process cruises, meteorological and hydrographic observations above should be made in addition to the following sediment and productivity measurements.
Sediment Composition Benthic Productivity and Standing Stocks carbon content foraminiferan production and biomass nitrogen content nutrients in pore water grain size mineralogy stable oxygen isotope abundance stable carbon isotope abundance
Mooring Program: One surface mooring contains 13 instrument packages. Instrument packages that measure fluorescence, beam attenuation, photosynthetically active radiation and oxygen are located at 10m, 20m, 35m, and 50m. The acoustic sensor for zooplankton biomass is at 40m. Conductivity and temperature sensors are at 8m, 13m, 18m, 48m, and 55m. Current meters are at 5m, 10m, 15m, 20m, 30m, 35m, 45m, and 50m. The meteorological instrumentation is on a discus buoy at the surface.
The four subsurface moorings contain either an upward-looking acoustic Doppler current profiler (ADCP) at 200 m or a profiling current meter and CTD. One subsurface profiling mooring contains a zooplankton biomass sensor at roughly 200m. The two upward looking ADCPs are also zooplankton biomass sensors.
Five separate subsurface moorings contain sediment traps (see Figure 2).
International Planning and Potential Collaborations with Other Programs: International planning for the Arabian Sea has been in progress since January 1991. The international planning group includes representatives from Pakistan, India, Oman, Kenya, Germany (chair), The Netherlands, United Kingdom, United States, and France. Of these, only France plans no field operations in the Arabian Sea. The Netherlands' Program commenced in 1992 and ends in 1993, and in a sense is a pilot study. It is collaborative with Kenya and Pakistan. In 1992 the U.S. and Pakistan began a four-year observational program in the northern Arabian Sea; this program is collaborative with the U.S. India has formed a JGOFS Committee, and the Indian Program will concentrate on the west coast of India and the central Arabian Sea in the 1994-1996 time-frame. The U.S. JGOFS planning group for the Arabian Sea has been approached by Oman for cooperation in setting up a JGOFS Time-Series Station on one of the coastal islands off Oman. Oman will be collaborating in the British, German, and U.S. JGOFS programs in the Arabian Sea. The Netherlands, the Intergovernmental Oceanographic Commission (IOC), with support from Germany, and the IOC in cooperation with the U.S. Office of Naval Research conducted training courses for regional scientists, with JGOFS methods/protocols being part of some of these courses. There is also an effort under way by the IOC to organize an exchange of scientists for data analysis. If the countries of the region each established and operated a JGOFS Time-Series Station in their territorial waters, the long-term scientific benefit would be substantial.
In an interagency meeting concerning research plans for the Indian Ocean, the 1994-1996 time-frame, with a focus on 1995, was identified by U.S. JGOFS for its Arabian Sea Process Study, by ONR for its Forced Upper Ocean Dynamics Program, and by WOCE for its World Hydrographic Program (WHP). The U.S. JGOFS sampling plan (Figure 2) has taken the U.S. WOCE WHP Plan into account and has identified some stations that overlap the U.S. WOCE WHP Plan; some lines in Figure 1 are part of the U.S. WOCE I7N line. Because U.S. JGOFS and U.S. WOCE are in the northern Indian Ocean at the same time, some of the U.S. JGOFS observations in the Arabian Sea are repeat hydrographic lines useful to U.S. WOCE. Additionally, the moorings for studying air-sea interaction and mixed layer dynamics which are part of the ONR Forced Upper Ocean Dynamics Program are necessary to understand the physical forcing which is part of U.S. JGOFS' goals, and to understand seasonal and possibly interannual variability of the region. Both the U.S. JGOFS Arabian Sea Process Study and the ONR Forced Upper Ocean Dynamics Program would like to turn their moorings around at the end of the field program and leave them in the Arabian Sea for an additional year. There have been preliminary discussions about this possibility, which clearly increases the understanding we can gain from the Arabian Sea
Implementation Schedule: This schedule contains plans of both the U.S. JGOFS Arabian Sea Process Study and the ONR Forced Upper Ocean Dynamics Program since these two investigations will work cooperatively on moorings and will coordinate use of a single research vessel. ONR's program is identified as NRL/SeaSoar.
Planning Meetings, Reports and Workshops:
A post-field work synthesis workshop and an international symposium to be held in the Netherlands are planned.
5.7.3 The Southern Ocean Process Study
The planning effort for U.S. JGOFS studies in the Southern Ocean began in earnest in 1990 (U.S. JGOFS Report 16), and has proceeded in parallel with the international planning effort (SCOR/JGOFS Report 10, 1992). The implementation summary presented here is taken from the U.S. JGOFS Southern Ocean Science Plan (U.S. JGOFS Report 17). A formal Implementation Plan was published in May 1995, U.S. JGOFS, Southern Ocean Implementation Plan (May 1995).
Rationale: The Southern Ocean, defined for the purposes of this study as the region south of, and including, the Subtropical Convergence, covers nearly 20% of the global ocean area. The Antarctic Circumpolar Current (ACC) has the largest volume flux of any major ocean current ( 130 Sverdrups). It is the only continuous circumglobal current, without beginning or end, and it is responsible for mixing of the deep waters of the other major oceans. Most of the ventilation of deep-sea water masses takes place in the Southern Ocean; in other words, deep water masses exchange gaseous components, including CO2 with the atmosphere. Furthermore, most deep waters derive their physical, chemical, and biological characteristics in the regions of the Southern Ocean where isopycnals outcrop at the sea surface and where mixing, cooling, and sea ice formation produce new water masses which sink into the ocean interior and renew the intermediate and deep waters of the world's oceans.
A unique feature of the Southern Ocean is the extensive regular seasonal advance and retreat of sea ice, oscillating between a maximum coverage of 20 106 km2 and a minimum of 4 106 km2. This surface feature, too, can be thought of as a frontal system, one that migrates north and south many hundreds of km annually. Biological productivity of surface waters is strongly influenced by the presence, and melting, of sea ice. Ice-edge productivity supports an abundance of life at higher trophic levels including mammals and birds as well as zooplankton and fish.
Fluxes of carbon in the Southern Ocean are large and play an important role in the global carbon cycle, yet the magnitudes of these fluxes remain poorly constrained. Our view of the air-sea exchange of CO2 in the Southern Ocean has undergone a substantial challenge during the past few years. Recent efforts at modeling the interhemispheric gradient of atmospheric CO2 have suggested that there is no net oceanic uptake of CO2 in the Southern Hemisphere (Keeling et al., 1989a and b; Tans et al. , 1990). If, as suggested, the net air-sea flux of CO2 in the southern hemisphere is close to nil, then it must reflect the compensating effects of large fluxes of CO2 into, and out of, the ocean in different regions. Takahashi et al. (1986) estimated that the largest CO2 flux into the sea, on a global basis, occurs in the zone between 40S and 50S. A counterbalancing net flux of CO2 out of high latitude waters in the Southern Ocean is expected to exist, the magnitude of this upwelling-induced efflux of CO2 is not well constrained by measurements of surface-water pCO2.
Global warming is likely to perturb circulation, ventilation, and biogeochemical processes in the Southern Ocean and these, in turn, represent potentially significant feedbacks into the nature of global change. At present, we know too little to predict the role of the Southern Ocean in global change, or the response of biogeochemical cycles in the Southern Ocean to anticipated warming. By successfully conducting process studies in the Southern Ocean, and then incorporating the results into ongoing efforts to construct coupled physical-biogeochemical models, we can better determine the present role of the Southern Ocean in the global carbon cycle, and improve our capability to predict the likely response of the region to anticipated global change.
Time Frame: Ship-of-opportunity and other pilot studies may begin during the austral summer of 1994-95. The major U.S. field program in the Southern Ocean will take place in 1995-96 and 1996-97. An announcement of opportunity for the main U.S. JGOFS Southern Ocean studies was issued in late 1993, with proposals due in mid-to-late 1994.
Objectives: The broadly-defined goals of the international JGOFS program have been articulated in a number of planning documents. These goals can be refined into more specific research objectives pertaining to the Southern Ocean:
Much of the variability of biogeochemical processes in the Southern Ocean can be ascribed to the different characteristics of the various zones described above. Therefore, in order to determine the magnitude and variability of carbon fluxes, and to understand the factors which regulate these fluxes, it is necessary that a JGOFS process study examine each of the zones. After considering the distinguishing characteristics of the diverse regions of the Southern Ocean, planning groups at both the national and international level have identified four general zones that represent the minimum number of subsystems having distinct biogeochemical properties that must be examined to provide a comprehensive assessment of carbon fluxes in the region. Physical, chemical and biological features within each zone have been thought to be sufficiently similar around the Southern Ocean that each zone can be considered as a continuous entity. The validity of that assumption needs to be tested, however, by comparing the results of the various national JGOFS process studies in different sectors of the Southern Ocean. The four representative zones include:
Program Elements: Like the Equatorial Pacific and Arabian Sea Process Studies, the strategy for studying the Southern Ocean includes:
JGOFS commenced with a Pilot Study in the North Atlantic, and its final Process Study will revisit the basin after 1998. The planning process for future work in the North Atlantic began with formation of an international planning group in 1992, and an international workshop in April, 1993. US JGOFS held a preliminary planning meeting in March, 1993, and a larger workshop in Bermuda in 1994 (US JGOFS Report #X). Scientific objectives for the US JGOFS North Atlantic Process Study were identified at that Workshop. The North Atlantic Process Study will provide US JGOFS with its only major opportunity to revisit a region of earlier study and test basin-specific hypotheses arising from analysis of earlier cruise results and other observations. Observations from the Bermuda Atlantic Time Series (BATS) as well as the North Atlantic Bloom Experiment ( NABE) were used to define priorities for future work.
There is ongoing research by European JGOFS programs in the eastern North Atlantic, and several nations are planning major studies for 1995-97. The major US campaign in the region will be in the period 1998-99, following the Southern Ocean Process Study.
Most analyses of interhemispheric gradients in atmospheric CO2, and assessments of CO2 sources indicate that the major global sinks for anthropogenic carbon are in the Northern Hemisphere. but, as an indication of our lack of understanding, is the sink terrestrial or oceanic? The North Atlantic has been identified as a potential major sink for anthropogenic carbon dioxide in part due to the siginificant amount of deep and intermediate water formation, yet current model estimates of the size of the North Atlantic CO2 uptake vary widely (eg, Sarmiento and Sundquist, 1992; Sundquist, 1993), attempts to constrain the anthropogenic flux are further complicated by the possibility of a net natural, background flux into the north atlantic (Broecker and Peng, 1992). the uptake of atmospheric CO2 can be estimated either directly, using seasonal maps of surface pCO2 and gas exchange rates, or indirectly, by computing the net advective divergence of CO2 for the basin. both approaches are at present plagued by a paucity of data on the appropriate scales. only a handful of meridional CO2 fluxes are currently available, all of which lack information on seasonal variability and the flux of doc. for surface pCO2, field work indicates a large amount of spatial variability (Watson et al., 1991) and a seasonal variabilty (Michaels et al., 1994; Keeling 1993) far greater than that in the atmosphere from which the long-term basin-scale averages need to be extracted.
Several recent lines of research have raised critical questions regarding the cycling and fluxes of carbon in the north atlantic. The JGOFS NABE studies revealed an unambiguous role of the biological pump in the seasonal drawdown of CO2 during the spring bloom, but quantitative budgeting of the relative importance of biological vs. physical processes in governing the seasonal CO2 cycle remains to be accomplished. The NABE sampling, unfortunately, did not observe the initial winter condition which precedes, and sets the stage for the bloom process. Studies of a local carbon budget constructed from the first five years of observations at the Bermuda Atlantic Time Series station indicate a greater than factor of 2 uncertainty in the balance between the observed seasonal drawdown in DIC and estimates of specific removal mechanisms (Michaels et al., 1994). More comprehensive sampling of the key properties and processes of the ocean carbon system are needed to improve our mechanistic and phenomenological understanding of the physical and biological pumps over an entire ocean basin. A recent analysis by Sarmiento (1995) suggests that CO2 uptake in the North Atlantic might be low with the DIC outflow to the south balanced by DIC/DOC supply through the Bering Strait and Arctic, rather than from atmospheric uptake. Narrowing the large uncertainties in the carbon budget for the North Atlantic basin is a critical task for JGOFS to address: without an effort to resolve our understanding of CO2 fluxes in this best studied and still poorly understood basin, JGOFS would not be complete.
Based on reviews of the NABE results and the considerations noted above, the US and international planning groups agreed that it was appropriate and timely for the next North Atlantic Process Study to focus on studies aimed at an improved answer to the question:
"What is the size of the CO2 sink in the North Atlantic Ocean?"
Answering this question not only means placing improved bounds on a new estimate, but improving our understanding of the processes contributing to the CO2 sink in the North Atlantic. The current estimates for the total oceanic uptake range from 0 to over 2 GtC yr-1, with the best ocean models giving 2 +/- 0.8 GtC yr-1 (Sarmiento and Sundquist, 1992). Achieving a satisfactory improvement will require an integrated program of time series, survey and process observations, remote sensing and modeling, as described below. The uncertainties in the carbon budget at basin and local scales suggest that an improved estimate requires improved understanding of carbon fluxes and transports, not merely more finely resolved data to estimate CO2 exchanges. Approaches to improved understanding are described below.
Finally, the final JGOFS Process Study will serve as a pilot study for future monitoring activities in the Global Ocean Observing System.
The US planning workshops identified the following as principal components for future work in the North Atlantic:
1. Constraining basin-scale carbon fluxes. The study would by necessity be seasonal and basin-scale (i.e. of larger spatial scale than NABE). It would emphasize novel techniques (biogeochemically instrumented buoys and/or drifters, underway systems, data assimilation) and would in many ways be a pilot study for future monitoring activities. The second North Atlantic study would incorporate elements from both a traditional process study and the expanded global survey (pCO2, Chl, nutrients) from the JGOFS science and implementation plans.
In a bit more detail, the study would involve extrapolating the seasonal pCO2 coverage for the basin using correlations among surface pCO2, hydrography, mixed layer depth, nutrients and would most likely rely heavily on data assimilation of field and satellite (wind speed, temperature, ocean color) measurements. Field work would be used to fill in critical gaps (many of them during the winter) of both surface pCO2 and its correlations with other variables and will emphasize "cheap" approaches (e.g. instrumented buoys, VOS) where possible.
2. Meridional flux estimates. A second thrust of the program would involve better estimates of the meridional fluxes of key biogeochemical variables (TCO2, NO3, PO4, DOC, DON, O2) from which the net divergence of carbon and nutrients for the North Atlantic could be calculated. The meridional fluxes would be estimated using the same approach as Brewer et al. (198?) but with seasonal resolution and improved constraints on the total flow field (from ADCP's pr IES') inverse modeling. These observations and sections will require a dedicated ship for a period of one year. The ship will alternate between regional pCO2 surveys and meridional sections, with seasonal coverage for each activity.
3. Control volume experiment near Bermuda. In order to close the Bermuda carbon budget, a better accounting of carbon removal by sinking particles (POC) and water motions and mixing (DOC, DIC) are required. Existing modeling and data assimilation tools will be applied in concert with observations from SeaWiFS, aircraft, biogeochemical moorings, routine time series cruises, and special process study cruises to balance the observed decline in surface concentrations of CO2 with specific process estimates of carbon export via sinking, DOC transport, etc. Fieldwork for a properly designed control volume experiment could be completed in a single field season, once moorings were in place and models were up and running. Some key core measurements are not made routinely, if at all, in BATS (e.g., grazing, 15N assimilation) and would need to be added for the process study.
The following are the highest priority measurements for each study. A more focused planning effort may add or subtract measurements from these lists:
1. Bermuda experiment: meteorology, CTD, oxygen, CO2 system properties, nutrients, particles (transmissometry and CHN analysis), DOC, pigments and optics. Particle flux from radiochemistry and floating traps. Optics, pCO2, oxygenand nutrients from moorings and drifters. Aircraft surveys of ocean color. New production, grazing rates and DOC utilization.
2. pCO2 and meridional carbon surveys: meteorology, CTD, oxygen, CO2 system properties, nutrients, particles (transmissometry and CHN analysis), DOC, pigments and optics. Underway CO2, nutrients, oxygen, pigments. DIC and DOC. SeaSoar mapping of upper ocean physical, chemical and optical fields.
Provisional implementation schedule:
The Bermuda Control Volume experiment could be carried out with a temporary enhancement of support for the time series study. Another control volume experiment could be carried out in 1986-7, concurrently with work by west European JGOFS nations in the Irminger Sea.
Elements of the zonal sections may be accomplished in collaboration with the WOCE Atlantic Program in 1996--1997. The pCO2 survey and meridional surveys might be carried out in conjunction with DOE- and NOAA sponsored work and WOCE operationsin the same time period. Large scale NSF support for coordinated and intensive process study observations is unavailable until after 1998.
6.1 Introduction and Rationale
The data sets obtained throughout the life of the U.S. JGOFS and the U.S. GLOBEC programs form the basis for scientific papers which collectively represent the legacy of both programs. The data sets will be used in the post-JGOFS era as test beds for models and as reference points for future studies. These data must be collected, carefully checked, properly assembled and made accessible to the user community. To this end, a data management system has been developed to meet program needs throughout and subsequent to its lifetime.
The U.S. JGOFS Long Range Plan outlined an approach to data management based on a distributed system of networked databases and a strong coordination effort. During the pilot studies, with funding from the NSF, the team of Glenn Flierl, James Bishop, David Glover and Satish Paranjpe developed prototypes of a networked, object-based data system. The NODC office at the Woods Hole Oceanographic Institution (G. Heimerdinger and R. Slagel) coordinated assembly and quality control of the data sets. While these efforts were successful as an interim measure, it was necessary to merge and expand these two activities.
With the initial development stage of a data management system ended, we needed to set in place an operational system which could efficiently handle the huge flow of data from the North Atlantic Bloom Experiment, the Equatorial Pacific Process Study and subsequent process studies (e.g., Arabian Sea, Southern Ocean, North Atlantic) as well as the accumulated data sets from the Time-Series stations at Bermuda and Hawaii, ocean color and CO2 survey data sets.
In response to this need, a proposal to implement data management was submitted to and funded by NSF. The proposal laid out a scheme designed
6.2 Approach and Definition of Program Data Management Needs
U.S. JGOFS and U.S. GLOBEC/George's Bank principal investigators require two distinct types of computer access: local data systems in which they can enter their data and work with them, and access to a much wider system containing data from other projects, as well as historical data sets. To accommodate the varied needs of PI's and other users, the JGOFS Data System was designed with maximum flexibility in mind.
Early in 1994, Glenn Flierl saw an opportunity to adapt the Data System server to the emerging technology of the World Wide Web. He altered the system's protocol to utilize HTTP, the HyperText Transfer Protocol. The major advantage in this change is to offer a standard, well-accepted interface to users of the Internet. This represented a turning point in the acceptance of the JGOFS Data Server since access to the Data System became easy and familiar; just like looking at other Web information.
In addition to observational data, the U.S. JGOFS program needs to be able to serve many other kinds of information - meeting and ship schedules, project abstracts, PI information, data status, etc. This needs to be readily accessible and kept up-to-date. Building and maintaining a WWW Home page seemed like the most effective way to meet this need and it goes hand-in-hand with the interface we chose to make the Data System available.
While the basic software structure is in place, many modifications and improvements can be anticipated. Thus, for the next several years, a system manager/programmer will be required. Another requirement will be additional storage capacity for the expanding data collection.
6.3 Structure of the Data System
The JGOFS data system was designed with a distributed, object-oriented approach. The guiding philosophy was that the closer we get to the actual data that the originating PI uses in her/his own research, the better. The storage format should be the PI's choice. To date, what we have discovered in the U.S. JGOFS program is that few PI's are able to or willing to serve their own data. Many reasons account for this - underpowered PC, unavailable HTTP server, lack of access to a networked Unix workstation - but, whatever the reasons, most of the investigators choose to send a copy of the data to the Data Management Office.
Nonetheless, the data can be stored in a format very close to that originally submitted. Since the system uses translation programs ("methods") to read the data and standard writing routines to create a common appearance, others can network to the data without regard to storage format or location. These methods know how the data are formatted, and the user of the system does not need to know it.
Although the core of the system is the distributed workstation structure, it is clear that there is a need for a central data management office to oversee and maintain a smooth operation. Full cooperation from program PI's will be necessary and here follows a breakdown of where these responsibilities lie and interrelate.
6.3.1 Data Management Office Responsibilities
The NODC data management effort during the North Atlantic Bloom Experiment has demonstrated the necessity for a data manager committed to collecting, tracking, and quality- controlling databases. In the future, such activities will be even more important and significantly greater in scope. Additionally, the personnel at the data management office are required to work with PI's to ensure that all data are properly documented.
Thus, the following activities are the fundamental responsibilities of the data management office:
Because of its responsibilities for ocean data archiving NODC has expressed interest in a continuing role in the U.S. JGOFS data management program. Coordination between NODC and the data system project is required to fully develop the data system structure and data management office plan. NOAA's National Oceanographic Data Center has supported this task with its Liaison Officer located at the Woods Hole Oceanographic Institution and has committed this resource for the long term. Clearly the effort envisioned is several times that expended during the Bloom Experiment and resources are required to ensure that the data activities function properly.
6.3.2 Principal Investigators' Responsibilities
The PI's, likewise, bear crucial responsibility for data management. In order to satisfy the requirement of JGOFS for data submission, the PI must:
6.4 The Data Management Office
To implement what has been outlined here, we have established the Data Management Office (DMO) in conjunction with the U.S. JGOFS Planning and Implementation Office, at the Woods Hole Oceanographic Institution.
For the near term future, and throughout the life of the program, we hope to continue to rely on the support from NODC, which they have provided in making the services of George Heimerdinger available to U.S. JGOFS data management. We look to the NODC for support for George's successor, when he chooses to retire, in a like manner. It is our belief that the linkage is a crucial one, both for NODC and for the U.S. JGOFS data management effort.
As the US JGOFS program moves from the data gathering to data analysis phase, the emphasis of the program is expected to focus increasingly on synthesis of the accumulated knowledge, incorporation into models etc. Access and use of the data by both experimentalists and modelers alike will require a data management system which has developed to meet these needs. The Data Management Office expects to work closely with the community to ensure that the accumulated data sets are available in a manner which will facilitate the synthesis process.
Including the contribution from NODC via its support of a liaison officer, the cost of operating the Data Management Office is approximately $350K per year. Depending on the maintenance needs subsequent to the end of the data acquisition phase of US JGOFS (which could continue data generation through 2001), the total cost of data management is estimated to be up to $2.5M.
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A time/element matrix has been assembled from the information in this plan, together with additional information external to this document, such as costs for the operation of the Planning and Implementation Office. Two points need to be noted in considering this matrix. Firstly, ship costs have not been factored in - for example, for the Arabian Sea Process Study, running at about 40-45% of research budgets at NSF. Second, the estimates included in this matrix include only these anticipated as coming from NSF. Substantial expenditures by other agencies have and, hopefully, will continue to come from other agencies supporting US JGOFS research. For example, ocean carbon through NOAA, measurements of the ocean CO2 system on WOCE lines through DOE, a variety of programs through ONR and satellite and airborne sensing studies through NASA. It will be instructive to try to develop additional matrices for each of these agency programs, so that they may be merged into a combined matrix which would provide the needed resource picture for US JGOFS in totality.
FY 96 97 98 99 00 01 02 So. Ocean P.S. 4500 9700 8500 4000 500 Arabian S.P.S. 5121 1464 Global Survey 1500 1500 1500 1500 Time-Series HOTS/BATS 1543 1728 1750 1760 1770 1790 1800 Moorings 1100 300 ? ? ? ? ? Auto. Instr. 700 250 ? ? ? ? ? Modeling and 760 760 2000 3500 4000 4500 5000 Synthesis Data Management 250 260 270 280 290 300 400 Planning/Implemt.774 1005 1064 1128 1341 1360 1380 and Synthesis
Totals 16248 16967 15084 12168 7901 7950 8580