Measuring circulation on a global basis has, however, proven a difficult and expensive task. Only recently have the required technologies started to catch up with theory in measuring ocean circulation. In a paper that appeared in the February 13 issue of Nature, MIT scientists and colleagues in Germany and Australia present a picture of circulation in the Western Mediterranean. Their work is based on a systematic combination of sophisticated computer models, highly accurate satellite altimeter measurements of the sea surface shape, and subsurface acoustic tomographic data of heat content. A much larger- scale version is now operating over much of the Pacific Ocean, and the intention is eventually to make the system fully global.
Climate change is inevitable, and the ocean is a major factor in that change.
However, our immediate goal is not to predict the ocean, but to determine to what degree it is predictable. In a related Nature article in the same issue, Professor Send and colleagues present acoustic tomography data for the Western Mediterranean. The data were gathered during an experiment on the feasibility of acoustically monitoring seasonal changes in the Mediterranean. Professor Wunsch said the work shows the capability which is emerging from a 20-year effort to develop observation and modeling techniques to the point where oceanographers can determine the motion of the ocean in time and three dimensions. In 1978, he and Professor Walter Munk of the Scripps Institution of Oceanography proposed the use of long-range acoustics for measuring the ocean and later pointed out the natural complementarity of acoustic tomography, satellite altimetry and numerical models for observing the oceans.