Mixing of the Storfjorden overflow (Svalbard Archipelago) inferred from density overturns

[1] Observations were made of the dense overflow from Storfjorden from a survey conducted at closely spaced stations in August 2002. The field data set consists of conventional conductivity-temperature-depth profiles and short-term moored current meters and thermistor strings. Finestructure estimates were made by calculating Thorpe scales over identified overturns using 0.1-dbar vertically averaged density profiles. Dissipation rate of turbulent kinetic energy per unit mass, epsilon, is estimated assuming proportionality between Thorpe and Ozmidov length scales. Vertical eddy diffusivity K-z is estimated using Osborn's model assuming a constant mixing efficiency. Survey-averaged profiles suggest enhanced mixing near the bottom with values of Kz and e, when averaged within the overflow, equal to 10 x 10(-4) m(2) s(-1) and 3 x 10(-8) W kg(-1), respectively. K-z is found to decrease with increasing buoyancy frequency as N-1.2 (+/- 0.3), albeit values of N covered only 0.5 - 8 cph (1 cph = 2pi/3600 s(-1)). Values of heat flux obtained using K-z suggest that the plume gains a considerable amount of heat, 45 +/- 25 W m(-2), when averaged over the thickness of the plume, from overlying waters of Atlantic origin. This value is lower than but, considering the errors in estimates of K-z, comparable with 100 W m(-2), the rate of change of heat in the overflow derived from sections across the sill and 80 km downstream.