Measuring Turbulent Stress and TKE Profiles in the OSBL using an Autonomous Underwater Vehicle.

Surface gravity waves are fundamental to the exchange of momentum, energy, heat, and gases between the atmosphere and the ocean. While considerable advances have been made in understanding wave-driven turbulent mixing in recent years, the specific nature of momentum exchange within the wave-affected surface layer remains a key gap in our understanding of the physical response of a coastal ocean to wind forcing. However, direct measurements of turbulent Reynolds stresses and dominant terms in the TKE budget in the oceanic surface boundary layer (OSBL) are rare owing to constraints associated with buoy-, ship-, and tower-based observations. Consequently, the inclusion of surface wave effects in turbulence closure schemes relies heavily on numerical modeling results due to the limited availability of direct observations.

Using a Hydroid-Kongsberg REMUS 600 autonomous underwater vehicle equipped with microstructure probes and fast velocimeters, measurements of the turbulent Reynolds stress, TKE, and dissipation were collected within the OSBL during a series of deployments carried out in the Santa Barbara Channel. Preliminary estimates of turbulent fluxes will be presented and analyzed in the context of boundary layer scaling relations. An analysis of vehicle response to wave orbitals and the subsequent correction and validation of turbulence measurements made from a propelled platform will also be discussed.