Physics of diurnal warm layers : turbulence, internal waves, and lateral mixing

Measurements of Near-Surface Turbulence and Mixing from Autonomous Ocean Gliders

“…This assertion is supported by the observations of Hodges and Fratantoni (2014), who directly observed an internal wave mode of the stable layer at the SPURS site during the period of our glider observations. Bogdanoff (2017) concludes that instability of the stable layer internal-wave mode is the only mechanism capable of supporting the turbulent dissipation rate levels measured by the glider. In the BoB, the warm, low-saline surface water overlying the cooler, saltier water below gives rise to a strongly stratified "barrier layer. "…”

“…The highest dissipation rates are observed during times of maximum insolation when the near surface is significantly stratified. This surprising result is discussed in the next section, following Bogdanoff (2017), who found that the energy from the thermocline internal wave field resonates with the surface stable layer to drive shear and turbulence.…”

“…Resonance occurs under certain conditions when the wavelength content of the deep internal waves matches a scaled relationship with the thickness of the surface layer, with the scaling dependent on the stratification parameters. Bogdanoff (2017) extended the D' Asaro framework to apply to the stable layer scenario, in which the thin stable layer assumes the role of the mixed layer in D' Asaro's model. Bogdanoff (2017) carefully considered the conditions applicable to the stable layer scenarios observed during SPURS, and found that the resonance condition likely occurs.…”

“…Bogdanoff (2017) extended the D' Asaro framework to apply to the stable layer scenario, in which the thin stable layer assumes the role of the mixed layer in D' Asaro's model. Bogdanoff (2017) carefully considered the conditions applicable to the stable layer scenarios observed during SPURS, and found that the resonance condition likely occurs. This assertion is supported by the observations of Hodges and Fratantoni (2014), who directly observed an internal wave mode of the stable layer at the SPURS site during the period of our glider observations.…”

Autonomous Multi-Platform Observations During the Salinity Processes in the Upper-ocean Regional Study

“…Observations from the T-gliders indicated the surprising role of the upperocean diurnal cycle in enhancing turbulence levels in the near-surface stable layer (Bogdanoff, 2017;St. Laurent and Merrifield, 2017, in this issue).…”