  We predict a new effect due to the presence of the global vorticity in
non-central relativistic heavy-ion collisions, namely a splitting of the
elliptic flow parameter $v_2$ at non-zero rapidity. The size of the splitting
is proposed as a new observable that can be used to constrain the initial
vortical configuration of the produced QCD matter in experiments. The new
findings are demonstrated by numerical calculations employing the parton
cascade model, Boltzmann Approach of MultiParton Scatterings (BAMPS), for
non-central Au + Au collisions at $\sqrt{s_{NN}} = 200 \ GeV$.
