To Abstract List
The objective of the ALACE program in the tropical and South Pacific is to gain enough direct observations of flow near 1000 m depth to be able to map the time-average flow and provide a level of known motion to reference geostrophic shear calculations based on the post-WOCE hydrographic data set. A total of 306 floats were deployed, most near 1000 m depth and most set to track currents for 26 days between surfacings. Over 540 float-years of observation have been collected. Over 60% of the floats are still operating and we expect to double the data collection over the next few years.
Preliminary calculations show (a) over the interior, flow can be mapped on approximately 500 km scale with accuracies of a few mm/s; (b) in the interior there are coherent patterns of large-scale flow that can be compared and contrasted with inferences from geostrophic shear and tracer distributions; (c) there are significant departures from these inferences but the qualitative scheme of circulation is similar to that found in Reid's study of the South Pacific; (d) the zonal flow near the equator is dominated by variability that shows some similarities with that found in numerical models forced by variable winds.
I would like to see the ALACE data used with the complete hydrographic data set to develop a quantitative decriptive model of the circulation of the tropical and South Pacific. This may be the best opportunity to see if the ocean works as we imagine or if there are some surprises to be discovered. Can the various transports be fit together over a whole basin without having to evoke excessive ageostrophy and/or excessive mixing. It is far from obvious that this can be done. In particular, speculations on the effect of rectified eddy flows by Gent & McWilliams and others raise the possibility that there are important transports that are not detected by either Eulerian mean current observations or by large scale shear calculations based on geostrophy.
To Pacific Workshop
To WOCE Home Page