Wind tunnel measurements were used to determine the unsteady location of shear-layer reattachment on a NACA 0012 airfoil with a leading-edge horn-ice shape, along with the corresponding time-resolved unsteady iced-airfoil performance. Similar trends in lowfrequency content were identified between the unsteady shear-layer reattachment location and the iced-airfoil performance. Conditional averaging was used to determine the average relationship between the unsteady reattachment location and the iced-airfoil performance corresponding to this common low-frequency mode. A phase relationship was also identified between the shear-layer reattachment location and the iced-airfoil performance. Changes in spectral content over time in the airfoil performance and reattachment location were analyzed using wavelet transforms. The low-frequency oscillations were observed to occur at similar time instances between these signals, and appeared to originate in the separation bubble at a location corresponding to nearly half of the separation bubble length. This lowfrequency mode was then propagated throughout the surfacepressure flowfield, affecting both the airfoil performance and the separation bubble length. A summary of the lowfrequency oscillation in the airfoil flowfield is presented.