Ice Albedo

Albedo is a measure of how much sunlight a surface reflects. Bare ice—bright and white—typically reflects about 50 percent of incoming sunlight, or solar radiation, while open ocean water, which is darker, reflects only 6 percent. Ice that is covered with snow has an even higher albedo, reflecting almost all of the light.

Snow and ice at the poles influence global climate because their high albedo reflects sunlight, keeping the poles cool relative to the equator. However, as global temperatures increase, more ice is melting.

As sea ice begins to melt, more of the ocean becomes visible, decreasing Earth’s planetary albedo. The reduced albedo means more solar radiation is absorbed into the ocean, which increases the ocean temperature. Warmer waters mean the ice takes longer to grow in fall and winter. The ice also melts faster in the spring and summer, which exposes darker ocean waters earlier, allowing more solar radiation to be absorbed for a longer period the next summer. The feedback cycle continues and the melting of ice is reinforced.

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Arctic sea ice grows every winter and melts to its smallest area at the end of the summer melt season. Watch the video to see how dramatically the amount of ice remaining at the end of every summer decreased between 1979 and 2015.