  We present results of a quantitative analysis of structured plasma outflows
above a polar coronal hole observed by the Atmospheric Imaging Assembly onboard
the Solar Dynamics Observatory spacecraft. In a 6-hour interval of continuous
high-cadence SDO/AIA images, we identified more than 2300 episodes of
small-scale plasma flows in the polar corona. The mean upward flow speed
measured by the surfing transform technique (Uritsky et al., 2013) is estimated
to be 122 $\pm$ 34 \kms, which is comparable to the local sound speed. The
typical recurrence period of the flow episodes is 10 to 30 minutes, and the
mean duration and transverse size of each episode are about 3-5 min and 3-4 Mm,
respectively. The largest identifiable episodes last for tens of minutes and
reach widths up to $40$ Mm. For the first time, we demonstrate that the polar
coronal-hole outflows obey a family of power-law probability distributions
characteristic of impulsive interchange magnetic reconnection. Turbulent
photospheric driving may play a crucial role in releasing magnetically confined
plasma onto open field. The estimated occurrence rate of the detected
self-similar coronal outflows is sufficient for them to make a dominant
contribution to the fast-wind mass and energy fluxes and to account for the
wind's small-scale structure.
