The Caribbean Sheets and Layers Transects (C‐SALT) Program

C‐SALT (Caribbean Sheets and Layers Transects) was a combined mesoscale, fine structure, and microstructure survey of the strong thermohaline staircase found in the tropical North Atlantic east of Barbados. This area lies at the confluence of the high‐salinity subtropical underwater at 150 m depth and the fresh Antarctic intermediate water at 750 m depth. The superposition of these two extrema gives rise to a very strong destabilizing vertical salinity gradient that can drive salt finger convection. During spring and fall 1985 the C‐SALT field program found an area of over 1 million km 2 , with staircase layering. The 5–30‐m‐thick layers were found to have horizontal coherence scales of hundreds of kilometers and revealed consistent temperature and salinity changes within layers. Tracer data imply enhanced vertical fluxes in the staircase relative to nearby regions; however, microstructure measurements indicate that the salt fingers were rather weak, at least in the fall. Direct shadowgraph observations suggest that the fingers were strongly tilted by the modest shears between layers. These results will require revisions in current models of salt fingering, but should contribute substantially to the goal of parameterizing the double‐diffusive mixing processes.