COHERENT STRUCTURES AT THE OCEAN SURFACE IN CONVECTIVELY UNSTABLE CONDITIONS

THE turbulent boundary layer at the ocean surface has some dynamical similarities to the atmospheric boundary layer1-4. The atmospheric turbulent boundary layer may exhibit not only random fluctuations but also spatially coherent, organized motion5,6. Thorpe1 conjectured that such organized motion should also be found in the upper ocean boundary layer in convectively unstable conditions. Here I report on observations made in the tropical Atlantic Ocean which confirm this view. Horizontal temperature profiles obtained at a depth of 2 m at night revealed ramp-like structures. Vertical velocity profiles in the upper few metres of the ocean was determined using a free-rising profiler, and exhibited abrupt changes corresponding to sudden changes in temperature. These features are known5,6 to be characteristic of spatially coherent, organized motions in turbulent boundary layers. © 1990 Nature Publishing Group.