Turbulent Fluxes

Miles McPhee

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My primary interest in MaudNESS is measuring how the turbulent structure of the upper ocean is affected by thermobaricity and other NES factors as the density contrast between the cold SML and underlying WDW weakens. In addition to the ANZFLUX data, winter profiles from other years appear to be potentially unstable to thermobaric effects (McPhee 2003). From a simple two-layer mixing scenario, I demonstrated that the competition between thermobaric enhancement of mixing and stabilizing buoyancy due to ice melt is highly dependent on the rate of turbulent heat transfer near the ice/ocean interface (McPhee 2003). In numerous polar experiments, my primary tool for directly measuring turbulent fluxes of momentum, heat, and salt has been the turbulence instrument cluster (TIC), which measures the 3-d flow field in the same horizontal plane as nearby temperature and conductivity sensors. When deployed at multiple levels in the boundary layer under sea ice, the TIC concept has been consistently productive, beginning from the first direct measurements of heat flux in an ocean boundary layer (McPhee et al. 1987), and including the first salinity flux measurements (McPhee 1994; McPhee and Stanton 1996). I have used results from these observations to construct and verify the similarity scaling arguments underlying LTC, including direct confirmation of local eddy viscosity derived from the vertical velocity spectrum (McPhee, submitted, J. Phys. Oceanogr.: ftp://psc.apl.washington.edu/mcphee/manuscripts/spectral_fluxes.pdf).

My second role in MaudNESS will be to coordinate project planning and preparation for the core process study in 2005, and to function as Chief Scientist during the cruise. Our planning includes acquiring the best possible remote sensing and weather data onboard, plus real time input from surrounding buoys by Iridium telephone (cf. C-7.10), and using these data in model forecasts of upper ocean conditions. We anticipate that the experiment will be complex, requiring a high degree of on-site flexibility and rapid response to changing conditions. By assembling a group with extensive polar experience, many of whom have functioned well together in the past, we believe we are well prepared to meet its challenges.

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