The Arctic Sea Ice is a positive feedback loop. (also referred to Ice-albedo Feedback).
The Arctic Ice plays a vital role in reflecting some of the suns rays. Believe in global warming or not – there is indisputable evidence that the amount Arctic ice is shrinking. When there is less ice to reflect the suns rays, more of the heat is absorbed by the less reflective ocean surface. This heating of the sea water leads to more of the ice melting. Thusly a Positive feedback loop- and a very dastardly system.