Ice Blink and Water Sky

White glare surrounded by dark cloud 

Ice blink and water sky are optical phenomena that occur in regions with large areas of ice and lying clouds so it's usually on the northern and southern area of earth, in Antarctica and Arctic. Both of these phenomena are related to each other. Ice blink refers to a white glare seen on the underside of low clouds that indicates a patch of snow or ice below, while water sky is a dark patch on the underside of lighter clouds indicating an open water area in a frozen sea.

How do these phenomena form? 
They form when light from the cut through a cloudy sky. The light will be continually reflected back and forth between the clouds and the surface of earth. Since open water absorbs more light than ice-covered surface, clouds above open water remain dark, while the light reflected by ice-covered surface creates bright clouds above it.

These phenomena are used by Inuit people and early European explorers to navigate or predict the presence of ice.