Group Leader:  Frank Muller-Karger

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

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

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

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

Group Leaders:     Frank Muller-Karger (represented by Denis Nadeau), Dan Redalje

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

Tasks:

1. Contact other groups active in coastal zone research -- Don Redalje?

a) Examine their current efforts in:

1. Effects of changes in external forcing or boundary conditions on coastal fluxes
2. Coastal biogeomorphology and global change
3. Carbon fluxes and trace gas emissions
4. Economic and social impacts of global change in coastal systems

b) Determine which contributions are or primary importance to the working group

These groups include:

• Land-Ocean Interactions in the Coastal Zone (LOICZ)

Note from LOICZ Joint Discussion: Continental margins: Source or sink of CO2?:
"The aim of this joint discussion session will be to better define the boundaries of continental margins, to clearly assign responsibilities for assessing various carbon fluxes at the margins, to bring the current understanding of sink and source terms at the margins into light, and to identify major needs to achieve global assessment. New evidence suggests that some of the continental margins are important sinks for atmospheric CO2. Surveys of carbon dioxide saturation in the North Sea and the East China Sea both showed significant undersaturation of CO2, implying they are sinks of carbon dioxide rather than sources. However, a simple linear extrapolation from these observations is unwarranted because the CO2 saturation conditions are highly heterogeneous. The source or sink terms of different types of margins need to be quantified separately, and the fate of terrigenous carbon discharged to the coastal zones and the newly sequestered carbon needs to be traced. Before these issues are settled, it is unlikely to obtain a reliable estimate of the net CO2 flux at the margins. Therefore, the vertical carbon fluxes of CO2 uptake at the margins and the horizontal fluxes of river discharged terrigenous carbon and the cross shelf export of shelf carbon need to be quantified in order to complete the global carbon cycle. Although JGOFS and LOICZ join forces supposedly to study continental margins and adjacent seas, the split in responsibilities remains unclear. In addition, the domains for study are not well defined in the IGBP Implementation plan. Therefore, it will be necessary to identify the outer boundaries of terrestrial ecosystems as covered by GCTE and the inner boundary of pelagic ecosystems as covered by JGOFS regional studies. Otherwise, some environments may be missed. Major questions follows: Which parts of continental margins are sources of CO2? Which are sinks? What is the net CO2 flux at the margins? What is the fate of terrigenous carbon and nutrients from river runoff? Are the continental margins well covered by IGBP projects? If they are, which projects cover which parts of continental margins? This joint session welcomes interested person from JGOFS, LOICZ, GCTE, BAHC, GAIM and other core projects to explore these issues. Useful products of this session might be a statement on the outer boundaries of the terrestrial ecosystems studied by GCTE or BAHC, a description of the boundary conditions needed by the ocean models at present and if possible, those needed in the future for nested models that couple global ocean models with fine-gridded continental margin models, and an action plan for the JGOFS/LOICZ joint Continental Margins Task Team in the future. (Kon-Kee Liu and Huasheng Hong)"

• Coastal Ocean Processes (CoOP)

"The coastal ocean has a number of unique physical and meteorological processes that promote high biological productivity, active sedimentary processes, dynamic chemical transformations and intense air-sea interactions. In addition to being an area of great scientific interest, the coastal ocean is a region of the global hydrosphere that has special societal importance. Key societal issues include coastal navigation, coastal hazards such as flooding and erosion, the utilization of renewable resources (e.g. fisheries) and nonrenewable resources (e.g. minerals, sand, and petroleum), while minimizing environmental damage. As more of the world´s population shifts towards coastal areas, human impacts on the coastal ocean in terms of pollution, waste disposal and recreation continue to increase. Sensible management decisions require greater fundamental comprehension of how the coastal ocean system functions. Research projects conducted under the auspices of CoOP are funded by the National Science Foundation, the Office of Naval Research and the National Oceanic and Atmospheric Administration."

• Oregon State Coastal Oceanography

• US Global Ocean Ecosystems Dynamics Research Program (GLOBEC)

• National Oceanographic Partnership Program (NOPP)

• Processes:
denitrification
calcification
production
• Fluxes:
micro/macro nutrients
DOC
DOM
air-sea exchanges

• definition of model boundary: from shore to boundary current
• establish range of depth for exchange between coastal and open ocean
• quantify DOC export from shelf to open ocean
• use POP(Parallel Ocean Program): Topex/Poseidon data, topography for inflow/outflow boundary begin with 1-D model (and ultimately progress to include in 3-D model) and with following features:   NO₃, Fe, PO₄, SiO₂, alkalinity, TCO₂, advection-diffusion equation, Ekman transport, geostrophic velocity, eddy flattening of isopycnals

Mary Elena Carr
mec@pacific.jpl.nasa.gov

Larry Anderson
landerson@whoi.edu

Don Redalje
donald.redalje@asm.edu

Jim Bauer
bauer@vims.edu

Anand Gnanadesikan
gnana@splash.princeton.edu

Group Leaders:   Frank Muller-Karger , Dan Redalje

Continuity:  There was agreement that this working group should continue; the team is revitalized and interest in this group appears to have grown.

Objectives:

• Understand the magnitude of the uncertainty caused by either ignoring or misrepresenting processes associated with margins.
• Coordinate integration of results from margin programs with other JGOFS scientists.
• Develop a strategy to incorporate margin processes into model assessments.

Interactions:

• Develop focused tests for GCM or other models.
• Coordinate with international JGOFS margins programs.

Resources: Needed resources were not yet clearly identified in the discussions.

NOTE:  The Continental Margins Working Group held a workshop on July 9, 2000, in Woods Hole (prior to the SMP summer meeting) to address some of the above issues, details of which are contained in the meeting report.

Group Leaders:   Dan Redalje, J. Bauer

The Continental Margins Working Group met on the afternoon of July 18 to discuss coastal issues relative to the goals and objectives of SMP.

Participants included:
 

Jim Bauer	bauer@vims.edu
Mark Brzezinski	brzezins@lifesci.uscb.edu
Wilf Gardner	wgardner@ocean.tamu.edu
Anand Gnanadesikan	gnana@splash.princeton.edu
Nicolas Gruber	ngruber@igpp.ucla.edu
Rick Jahnke	rick@skio.peachnet.edu
Don Redalje	Donald.Redalje@usm.edu
Don Rice	drice@nsf.gov
Mike Roman	roman@hpl.umces.edu
Taro Takahashi	taka@lamont.ldeo.columbia.edu

In previous years, the SMP Continental Margins Working Group had the objective of assessing the role of the ocean margins and pelagic-margin exchange in the global carbon cycle and to lay the groundwork for incorporating the coastal environment into general circulation models (e.g. see 1998, 1999, and 2000 Working Group Reports (above) and the report of the 2000 SMP Continental Margins Workshop). This year, the group reexamined these issues relative to the results obtained by the Ocean Margins Program (OMP) and other similar projects (e.g. OMEX and LOICZ). Initial questions included: How important are continental margins in the global carbon cycle? Do these areas act as sources or sinks for CO₂? What are the magnitudes of the carbon fluxes and transports in coastal regions? What products do coastal programs need to produce so that continental margins can be incorporated into global carbon models?

The Ocean Margins Program, funded through SMP, is in the final stages of synthesizing its findings and linking the data to the U.S. JGOFS SMP web site. A special issue of Deep-Sea Research II will include more than 20 papers that address various aspects of the OMP study. One of the most important results from this program is the finding that over the course of the OMP field study, the Mid-Atlantic Bight (MAB) was net autotrophic resulting in an export of 4-7 MT C y^-1, primarily in the form of DOC, to the open ocean. As the results of the OMEX and LOICZ programs become available, it will be possible to compare those findings to the combined SEEP I, SEEP II and OMP results and conclusions.

The group then discussed the future of coastal programs within the context of the next generation of carbon cycle research. It was suggested that it might be important to gain a better understanding of the transports in ocean margin environments prior to initiating further carbon cycle process studies. It may be advantageous to develop comprehensive physical models of the systems before moving to carbon cycle process studies as well. For example, the GLOBEC Georges Bank study began with the development of physical model before any biological data were collected. This may serve as a model approach for further ocean margin carbon cycle research. Another suggestion was that coastal programs in other margin regions might want to follow the OMP model and study the large-scale distributions of properties to give a comprehensive description of the processes active in those areas.

It was pointed out that many margin programs have focused on "along-shore" physical flows (e.g. OMP). However, "cross-shelf" exchanges and eddy transports can be of major importance to carbon cycling and transport. Many of the models of cross-shelf exchanges provide results that are not always in agreement. Thus, it becomes important to gain a better understanding of these cross-shelf exchanges in addition to along-shelf transports within the context of carbon cycle research and model development.

The group also discussed the impacts of changes in land use relative to export of carbon from the terrestrial environment to the coastal oceans. Much of the organic carbon from terrestrial sources may remain in catchments rather than be transported to coastal waters due to these changes in land use patterns. This is another area where further research is necessary before we can accurately assess the global carbon budget.

Another area of discussion for the group was the need for enhanced instrumentation in continental shelf regions (e.g. the coastal Global Ocean Observing System). This approach could provide a great amount of data as well as allow us to use at-sea research funds more effectively. It would be important to insure that all of the coastal regions have instrumentation that provides a consistent and standard set of data and that all of the observing systems are linked together. In this way, we can make most effective use of the observations and the funds available. This approach would also allow us to make observations over much longer time scales than are possible using the week/month research cruise paradigm.

We discussed several other areas of uncertainty relative to the role of margins in the global carbon cycle.  One of these areas is the impact of rivers and buoyancy driven circulation on the fate of organic carbon. What do we know about the delivery of sediments and organic carbon to coastal waters via rivers? How do we measure this effectively? To this end, NSF has funded the upcoming RiOMar Workshop (River-dominated Ocean Margins, Nov 1-3, 2001, Tulane University) that will address the importance of rivers in the introduction of materials to the coastal oceans and there will also be an RFP issued for the CoOP Buoyancy Driven Transport Process Study.  Another area of uncertainty is the importance of groundwater input of carbon to coastal waters. Although these processes may be better understood in some areas (perhaps those with LTER programs or where watershed Total Minimum Daily Load [TMDL] studies have been conducted), the importance of these processes and carbon input mechanisms are relatively unknown.  A third area of uncertainty that needs to be addressed is the input of alkalinity to coastal waters by rivers. It may be that as much of 0.6 GT y^-1 of alkalinity is introduced to ocean margins by rivers. One of the difficult challenges in this regard is that we do not have an effective method for measuring alkalinity in fresh water. Thus, our inability to make accurate measurements leads to a fundamental lack of understanding as to the importance of this process.

The last part of the meeting focused on the future of ocean carbon cycle research. It was emphasized that the direction for future study has not yet been fully defined. However, ocean margins will be included as a program component. At present, it appears that a number of medium-sized programs that could possibly lead to larger scale or process studies may be the models for carbon cycle research in the near future. A program announcement in this regard is planned for Fall 2001.

From the discussions of the Continental Margins Working Group, it is clear that there is a need for coastal issues to be fully integrated in the next model for ocean carbon cycle research. In addition, there are many areas where further research is needed before we can accurately determine the impact of margin processes on the global carbon cycle. The challenge facing the ocean margin research community is to make sure that coastal processes that make significant contributions to the global carbon cycle are addressed in an effective manner within the next decade of ocean carbon cycle research.