nificance to the large-scale flow. This has been shown in idealized contexts by Bretherton and Haidvogel (1976), Holloway (1978, 1987), and Treguier (1989). It seems particularly relevant for the Antarctic Circumpolar Current (McWilliams et al., 1978; Treguier and McWilliams, 1990; Wolff et al., 1991), and it also is probably so for the continental slopes (Holloway, 1992). Unfortunately, it currently is not included as a SGS process in most large-scale ocean models.

  1. Material Property Mixing. The boundary regions of the ocean, including the continental shelves and marginal seas, have especially high biological productivity, anomalous chemical sources because of river runoff and human pollution, and strong local mixing because of both strong tidal flows and shallow depths that permit the boundary layer to encompass the whole water column. These processes are not commonly part of the SGS parameterizations in large-scale ocean models.

  2. Rapid Communication in the Boundary Wave Guide. The sides of ocean basins can support a rich variety of coastal waves (LeBlond and Mysak, 1978). In the simplest geometry, with vertical sides, these waves are Kelvin waves. They have an off-shore scale of the deformation radius (tens of km) and travel at the rapid speed of short gravity waves. They play an important dynamical role in communicating changes in the boundary-pressure distribution along the coastline and establishing along-shore currents of deformation-radius width. Since this scale lies in the SGS range for large-scale ocean models, there is a question of how to incorporate these effects adequately. Milliff and McWilliams (1994) have shown that the outcomes of these communication events by waves can at least sometimes be accurately represented by simple, integral consistency constraints on the large-scale fields.

SEA ICE

A sea-ice parameterization is a necessary element of an oceanic climate model. In its simplest, most often used form, it is merely a thermodynamic model for a temperature profile within a layer of ice of a certain thickness. The parameterization allows for storage of heat and water and alteration of the air-sea fluxes. Yet it is also important to model both sea ice's concentration, since the fraction of open water (or leads) makes an enormous difference to the air/sea heat and water fluxes, and its horizontal movements. Modeling the concentration and movements requires the inclusion of mechanical dynamics as well.

In our own modeling studies, we are following the formulation of Hibler (1979), in part as it has been extended by Lemke et al. (1990) and by Flato and Hibler (1990).

BIOGEOCHEMICAL PROCESSES

Oceanic biochemistry is a necessary element of any oceanic climate model that addresses either the oceanic distributions of nutrients, oxygen, and so on, or the global cycle for CO2, et al. I hesitate to declare a common current practice for ocean models, but guidance can be found in the recent study by Sarmiento et al. (1993).

Scott Doney, David Glover, and Raymond Najjar are developing a simple ecosystem model for the upper ocean that is based on the flow of nitrogen among organic and inorganic constituents. A solution for the annual cycle in the Sargasso Sea near Bermuda is shown in Figure 12. There are some attractive features: the timing of the spring phytoplankton bloom that follows the wintertime renewal of nutrients by deep PBL mixing and ends with their depletion in the well-mixed layer; the summertime subsurface maximum of phytoplankton that live on the border between nutrients in the seasonal pycnocline and penetrating solar radiation; and the somewhat deeper subsurface maximum in nutrients associated with the remineralization of sinking particles below the solar penetration.

ACKNOWLEDGMENTS

It seems increasingly clear to me that any serious climate modeling that goes beyond the initial conception of new possibilities requires the cooperation of many scientists. The scope and tasks are so large that pooled knowledge and labor seem nearly essential. In this spirit, I would like to thank my current partners in the work touched on in this paper: Bruce Briegleb, Gokhan Danabasoglu, Scott Doney, Peter Gent, Jeff Kiehl, Bill Large, Chin-Hoh Moeng, Jan Morzel, Ralph Milliff, Nancy Norton, Breck Owens, Mike Spall, Peter Sullivan, and John Wyngaard. In addition, I thank Kirk Bryan for his comments both during the workshop and in a review of this manuscript. The work is sponsored, under various contracts, by the National Science Foundation and the National Oceanic and Atmospheric Administration.



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