Derivation of energy loss via coupled modes

A coupled mode formalism can describe energy loss within an ocean waveguide due to all possible mechanisms, including bulk attenuation, scattering from rough surfaces, and volume inhomogeneities. First order corrections produced from mode-couplings can be incorporated into the modal loss. Accounting for these losses within an adiabatic mode approach would provide improvements over current standard modal propagation models. Highlights of the formalism for scattering from a rough surface will be provided.