A vicious circle is a chain of events which reinforce themselves through a positive feedback loop, resulting in events spiraling out of control, ultimately leading to a destructive outcome. The melting of the polar ice caps is an example of a vicious cycle, as the reflective ice caps melt they reflect less sunlight and heat back to the atmosphere, with more of this heat being trapped by the dark ocean which is now exposed by the loss of ice cap. This retained heat then increases the temperature feeding back to induce the melting of more ice caps creating what we would call a vicious circle.