  We model the spectra and light curves of circumbinary accretion disks during
the time after the central black holes merge. The most immediate effect of this
merger is the dissipation of energy in the outer regions of the disk due to the
gravitational wave energy and linear momentum flux released at merger. This has
the effect of perturbing the gas in the disk, which then radiates the
dissipated energy over a cooling timescale, giving a characteristic infrared
signal for tens of thousands of years when the total black hole mass is M~10^8
M_sun. On the basis of a simple cosmological merger model in which a typical
supermassive black hole undergoes a few major mergers during its lifetime, we
predict that ~10^4-10^5 of these IR sources should be observable today and
discuss the possibility of identifying them with multi-wavelength surveys such
as SWIRE/XMM-LSS/XBootes and COSMOS.
