Binary black holes emit gravitational waves (GWs) as they inspiral towards coalescence. Searches for electromagnetic counterparts to GWs rely on looking for common sources producing both waves. Here, we take a different approach: we investigate the impact of the binary binary hole onto its outer circumbinary disk in the radiation/wave zone, using general relativistic hydrodynamical simulations and a general relativistic ray-tracing code. We show that in the radiation/wave zone, retardation effects and GWs leave an imprint onto the disk, leading to quasi-periodic patterns in the electromagnetic lightcurve.