Low-energy reactive ion scattering (RIS) experiments show that NaCl dissociates almost completely on condensed ice surfaces prepared on Ru(001) even at 100 K forming solvated ions. NaCl by itself does not dissociate on a Ru(001) substrate; however, submonolayer coverages of water sets-in dissociation, Na+ ions thus created are immobile such that they do not migrate across one water bilayer (BL) over several minutes. Accumulation of positive charge at the ice surface makes Na+ diffuse into the sublayers.