The recombination dynamics of 3P oxygen atoms on cold amorphous solid water to form triplet and singlet molecular oxygen (O2) is investigated under conditions representative of cold clouds. Reactive molecular dynamics simulations including Landau-Zener-based hopping to account for nonadiabatic transitions find that both ground-state (X3Σg-) O2 and molecular oxygen in the two lowest singlet states (a1Δg and b1Σg+) can be formed and the molecular species stabilize through vibrational relaxation. The relative populations of the species are approximately 1:1:1. These results also agree qualitatively with a kinetic model based on simplified wavepacket simulations. The presence and stabilization of higher electronic states of O2 are expected to modify the chemical evolution of cold interstellar (T ∼ 10-50 K) and warmer noctilucent (T ∼ 100 K) clouds.