Vertical Velocity in the Upper Ocean

The project involves an oceanographic field experiment to obtain direct measurements of vertical velocity in the upper ocean – a dynamically important but poorly observed component of ocean circulation. Vertical velocity in the upper ocean plays a central role in ocean dynamics and in the vertical fluxes of heat, salt, gases, and carbon, making it a key element of the coupled Earth system. Quantifying these processes requires a clear quantitative and dynamical understanding of the structure and variability of vertical velocity and will lead to improvements in ocean models which are essential components of modern coupled weather and ocean prediction systems. Measurements of vertical velocity in the ocean are difficult, rare, and usually indirect, with outcomes sensitive to the assumptions and scales of the chosen method. Because of these challenges, much of our current understanding is based on simulations, with their own imperfect assumptions. In this project, a fleet of specially designed, subsurface Lagrangian floats, equipped with velocity profilers, will directly measure vertical velocity along an isopycnal located just below the evolving mixed layer of the Sargasso Sea. The observing program will span a full annual cycle through a sequence of 60-day missions staged out of Bermuda. Satellite observations of sea surface height, sea surface temperature, and ocean color will be incorporated into the study. Statistical characterization of the measurements will be compared with output from high-resolution numerical simulations. Additional independent vertical-velocity data products will be incorporated into the validation effort as they become available. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.