  We study the generation of 2D turbulence in Faraday waves by investigating
the creation of spatially periodic vortices in this system. Measurements which
couple a diffusing light imaging technique and particle tracking algorithms
allow the simultaneous observation of the three-dimensional fluid motion and of
the temporal changes in the wave field topography. Quasi-standing waves are
found to coexist with a spatially extended fluid transport. More specifically,
the destruction of regular patterns of oscillons coincides with the emergence
of a complex fluid motion whose statistics are similar to that of
two-dimensional turbulence. We reveal that a lattice of oscillons generates
vorticity at the oscillon scale in the horizontal flow. The interaction of
these vortices explain how 2D turbulence is fueled by almost standing waves.
Remarkably, the curvature of Lagrangian trajectories reveals a "footprint" of
the forcing scale vortices in fully developed turbulence. 2D Navier-Stokes
turbulence should be considered a source of disorder in Faraday waves. These
findings also provide a new paradigm for vorticity creation in 2D flows.
