We present evidence for the rapid variability of the high velocity iron K-shell absorption in the nearby ($z=0.184$) quasar PDS456. From a recent long Suzaku observation in 2013 ($sim1$Ms effective duration) we find that the the equivalent width of i
ron K absorption increases by a factor of $sim5$ during the observation, increasing from $<105$eV within the first 100ks of the observation, towards a maximum depth of $sim500$eV near the end. The implied outflow velocity of $sim0.25$c is consistent with that claimed from earlier (2007, 2011) Suzaku observations. The absorption varies on time-scales as short as $sim1$ week. We show that this variability can be equally well attributed to either (i) an increase in column density, plausibly associated with a clumpy time-variable outflow, or (ii) the decreasing ionization of a smooth homogeneous outflow which is in photo-ionization equilibrium with the local photon field. The variability allows a direct measure of absorber location, which is constrained to within $r=200-3500$$rm{r_{g}}$ of the black hole. Even in the most conservative case the kinetic power of the outflow is $gtrsim6%$ of the Eddington luminosity, with a mass outflow rate in excess of $sim40%$ of the Eddington accretion rate. The wind momentum rate is directly equivalent to the Eddington momentum rate which suggests that the flow may have been accelerated by continuum-scattering during an episode of Eddington-limited accretion.
