Restratification of Mixed Layers

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Traditional models and paradigms of the upper ocean vertical stratification rely on dynamics that take place in only the vertical dimension. Atmospheric forcing and turbulent processes create a "mixed layer" in the uppermost surface of the ocean. However, recent measurements in the North Pacific indicate that the water may have horizontal gradients of temperature and salinity and these may "slump" over. This project will conduct field work to examine the "slumping" process to determine how it plays a role in establishing the vertical stratification of the mixed layer. They will make measurements of temperature and salinity profiles at one location and will use the ship to sample a grid to capture three dimensional structures of temperature and salinity. Their goals are to observe the evolution of the slumping process and to obtain estimates of the forcing and dissipative terms which drive the slumping and to determine the horizontal length scales of the slumping which will give an indication of the physical processes that halt the slumping process. They will also investigate whether the size of the density contrasts depends on the larger-scale mean density gradient and this will determine whether the density contrasts can be predicted by combining combining one-dimensional dynamics and larger scale gradients. The datasets will be suitable for testing others' models of the three-dimensional mixed layer.