Report 18 -- Strategies C

## Specific Issues for Coupled Models

Several European nations have JGOFS process studies underway in the Atlantic sector of the Southern Ocean, and U.S. JGOFS AESOPS in the Pacific sector will take place during 1996-98. The U.S. GLOBEC Southern Ocean program is planned for 1999-2000. After these studies have been completed, it is unlikely that other field programs of this magnitude will be conducted in the Southern Ocean in the foreseeable future. Thus all attempts to advance our understanding of the Southern Ocean system after 2000 will, by default, rely more heavily on remote sensing capabilities, moored instruments and models than on direct observation and experimentation at sea. This situation means that the window of opportunity provided by the JGOFS and GLOBEC field programs of the U.S. and other nations in the Southern Ocean will be of the most lasting scientific value if those programs address questions that:

- pertain to scientific problems that are of significant magnitude at the regional and/or global scale,

- are clearly unanswered at present,

- require direct observation and experimentation at sea to answer them, and

- can help in the future development of models (both physical and biogeochemical) and long-term monitoring strategies that may be able to predict and/or measure responses of the Southern Ocean to any future changes in climatic forcing.

Here we give six scientific questions of that kind and discuss their implications, both for the 1996-98 AESOPS field program and for modeling efforts. Although we have phrased these questions in terms of JGOFS, similar issues could be formulated for GLOBEC. Rather than endorse specific field programs or specific models, we consider general questions that the JGOFS field programs in the Southern Ocean are well positioned to address.

1. Is the Southern Ocean a net source of CO2 to the atmosphere or a net sink? Of what magnitude?

2. Do biological processes matter quantitatively in atmosphere/ocean CO2 exchange in the Southern Ocean?

3. What controls primary production in the Southern Ocean?

4. What controls export of organic matter to the deep ocean?

5. Do ice and ice biota influence the system?

6. What are the sediments telling us?