Abstract
First-ever measurements of the turbulent kinetic energy (TKE)
dissipation rate in the northeastern Strait of Magellan (Segunda
Angostura region) taken in March 2019 are reported here. At the time of
microstructure measurements, the magnitude of the reversing tidal
current ranged between 0.8 and 1.2 ms-1. The probability distribution of
the TKE dissipation rate in the water interior above the bottom boundary
layer was lognormal with a high median value εmed =1.2x10-6 Wkg-1.
Strong vertical shear, (1-2)x10-2 s-1 in the weakly stratified water
interior ensued a sub-critical gradient Richardson number,
Ri<10-1-10-2. In the bottom boundary layer (BBL), the vertical
shear and the TKE dissipation rate both decreased exponentially with the
distance from the seafloor ζ, leading to a turbulent regime with the
eddy viscosity KM~10-3 m2/s, which varied with the time
and location, while being independent of the vertical coordinate in the
upper part of BBL (for ζ>~2 meters above
the bottom).