Summary of Activities
At the Southampton Oceanography Centre, we are using the Miami Isopycnic-Coordinate Ocean Model (MICOM) to investigate the circulation and processes in the World Ocean. This work is part of that undertaken by the Large-Scale modelling team in the James Rennell Division for Ocean Circulation and Climate.
This work started in 1990, initially implementing a model of the North Atlantic (using monthly climatological forcing and realistic bathymetry and initial conditions) at a horizontal resolution of about 1 degree, in the AIM (Atlantic Isopycnic Model) project. The model was spun-up for several decades and used to study the ventilation of the subtropical gyre, patterns of tracer distributions, interdecadal variability of the upper ocean water masses (see references 1-4) , and water mass formation rates (reference 7). The model was also compared with a Bryan-Cox level model set up by the Hadley Centre for Climate Prediction and Research (part of the UK Met. Office) to be as similar as possible, and major differences were noted to result from the way in which the two models handled the overflows of the deep water masses from the Greenland-Iceland-Norwegian Seas (references 5, 6).
The work then extended in two new directions. Firstly, an eddy-permitting Atlantic model was implemented at 1/3 degree resolution, and integrated for 20 years. This integration has been intercompared with a similar Bryan-Cox model run at Kiel University, and with a terrain following coordinate model (SPEM) run by Grenoble University in the " DYNAMO: Dynamics of North Atlantic Models" project, which is funded by the CEC (contract number MAS2-CT93-0060 ). We have also implemented MICOM on a fully global grid (at about 1 degree resolution), which has involved converting the code to run on non-square grid boxes, and with different time-steps in different parts of the domain. The global model has been used to diagnose water mass transformation in the Southern Ocean (reference 8) and has also been compared with a similar Bryan-Cox model implemented at the Hadley Centre.
Personnel
Adrian New: Project Leader
Yanli Jia: Isopycnic Modeller (Atlantic Models)
Alex Megann: Isopycnic Modeller (Global Models)
Bob Marsh: Model analysis and sensitivity studies
Recent Publications
1. New, A. L., R. Bleck, Y. Jia, R. Marsh, M. Huddleston and S. Barnard, 1995: An isopycnic model study of the north Atlantic. Part 1: model experiment. J. Phys. Oceanogr., 25, 2667-2699.
2. New, A. L. and R. Bleck, 1995: An isopycnic model study of the North Atlantic. Part 2: interdecadel variability of the subtropical gyre. J. Phys. Oceanogr., 25, 2700-2714
3. Jia, Y. and K. J. Richards, 1996: Tritium distributions in an isopycnic model of the North Atlantic. J. Geophys. Res., 101, 11883-11901.
4. Marsh, R. and A. L. New, 1996: Modelling 18 degree water variability. J. Phys. Oceanogr., 26, 1059-1080.
5. Roberts, M. J. , R. Marsh, A. L. New, and R. A. Wood, 1996: An intercomparison of a Bryan-Cox type ocean model and an isopycnic model. Part 1: the subpolar gyre and high latitude processes. J. Phys. Oceanogr., 26, 1465-1527.
6. Marsh, R. , M. J. Roberts, R. A. Wood, and A. L. New, 1996: An intercomparison of a Bryan-Cox type ocean model and an isopycnic ocean model. Part 2: The subtropical gyre and meridional heat transport. J. Phys. Oceanogr., 26, 1528-1551.
7. Nurser, A. J. G. , Marsh, R. and Williams, R. G., 1999: Diagnosing water mass formation from air-sea fluxes and surface mixing. J. Phys. Oceanogr., 29, 1468-1487.
8. Marsh, R., Nurser, A. J. G., Megann, A. P., and A. L. New, 1999: Water mass transformation in the Southern Ocean of a global isopycnic coordinate GCM. Journal of Physical Oceanography, in press.