Turbulent mixing in stratified flows is described by mixing efficiency. This mixing efficiency compares the energy used in irreversible mixing, enlarging the minimum gravitational potential energy that can be kept in the density field, to the
entire change in mechanical energy during the mixing process. It can be defined either as an integral quantity, calculated between  inert initial and final conditions or as a fraction of the energy flux to mixing and the power into the system. These two definitions can give different values if the system is not in steady state. Mixing efficiency is especially important in oceanography as mixing is required to keep the overall stratification in a steady-state ocean. The entire amount of mixing in the oceans is equal to the product of the power input to the ocean and the mean mixing efficiency.