Ocean models at eddy-permitting resolution are generally overdissipative, damping the intensity of the mesoscale eddy field. To reduce overdissipation, backscatter parameterizations introduce an artifical energy pathway from small to large scales to close the energy cycle. In this talk, I will review the underlying issue, compare several possible deterministic, stochastic, and data-driven approaches, and present mathematical results regarding well-poseness and stability of the underlying parameterized PDE.