Submesoscale Mixed-Layer Dynamics: Isolating the Sub- and Super-inertial

Eric Kunze1, James B. Girton2, John Mickett2 and Tom Farrar3

1NorthWest Research Associates, Redmond, WA

2Applied Physics Laboratory, University of Washington, Seattle, WA

3Woods Hole Oceanographic Institutions, Woods Hole, MA

The ocean mixed-layer is both conduit and barrier for exchange of momentum, heat and gases between the atmosphere and ocean. Recent modeling has revealed a host of competing submesoscale mixed-layer processes which can either promote or inhibit air-sea exchange. These processes are an observational challenge because of the need for unaliased temporal and lateral resolution, as well as sufficient duration to establish persistent mechanisms.

We plan to improve understanding of 110 km scale lateral processes in 3-D mixed-layer dynamics with a 28-day experiment in the North Pacific Subtropical Front, a region of above-average atmospheric forcing, typical mid-ocean mesoscale advection and straining, and typical submesoscale activity, maximizing the likelihood of finding significant signals. Multiple ship surveys, profiling float array deployments (1620 floats measuring T, S, horizontal velocity and microstructure) and a drifting air-sea flux platform will sample the upper-oceans response to winter storm forcing in the presence of the mixed-layer fronts that characterize the central ocean gyres. The arrays will profile in sync every 3040 minutes to eliminate space-time aliasing, cycling between the surface and 100150 m depth (below the transition layer). During and between deployments, the region will be surveyed repeatedly with (i) the SWIMS towyo body and shipboard ADCP to provide larger-scale context and (ii) a multi-depth flow-through temperature and salinity system to resolve smaller horizontal scales in the upper 25 m.

The WHOI contribution to this project is to deploy a drifting surface flux buoy with subsurface drag elements intended to keep the buoy with the array of floats.

Page updated: December 9, 2016 by Benjamin Greenwood