>> reporter: and the more greenland melts, the more it speeds up the melting process. take the large melt lakes that are forming on top of the ice sheet. stunning to look at, but bad news for the ice. these lakes are deceptively beautiful, because whereas the white of the ice actually reflects the sunlight, the piercing blue of the lakes actively absorbs it, heating them up and then accelerating the rate of melt. perhaps the clearest example of this vicious melt cycle can be seen in greenland's many glaciers. a glacier is a mass of thick ice that moves under the force of its own weight, like a slow river into the sea. but as melt water moves through the ice, it softens it, draining to the bed, where it then lubricates the movement of the glacier. we got a rare, close-up view of one of greenland's