Eddy viscosity from bottom Ekman veering profiles

Abstract

ADCP profiles near the sea bed, at a 130 m depth continental shelf, were used to estimate the mean veering of the velocity vectors using a complex correlation coefficient. An analytic expression for the veering vertical gradient (∂θ/∂z) as function of turbulent Ekman layer thickness (δE) was developed and, using constant eddy viscosity assumptions, sea bottom stress and additional turbulent boundary layer features were evaluated. Further statistics on the time series yields median values for δE of about 13 m, eddy viscosity Az = 4.2×10−3 m2s−1 and median bottom stress of 9.2×10−2 Pa, thus leading to high Reynolds numbers. Very good agreement is obtained between observations and bottom Ekman balance solutions according to determination coefficients assessed (R≥0.99).