Christian Seis - Westfälische Wilhelms Universität Münster We consider parallel mixing by advection and diffusion modelled by the linear advection-diffusion equation for general velocity fields with bounded enstrophy. We present optimal estimates on the rates of decay of the L2 norm, which describes the phenomenon of enhanced dissipation, and we deduce bounds on the rates of decay of the H−1 norms, which describes the effect of mixing. The results show that the optimal time scales for both phenomena are of the order of a logarithm of the diffusivity constant.