  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 iron 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.
