in the Polar region is expected to be some of the largest and most rapid, and will cause major physical, ecological, sociological, and economic impacts, especially in the Arctic, Antarctic Peninsula, and Southern Ocean. In the Arctic, warming is occurring faster than the global mean. From 1978 to 2004, perennial sea ice cover in the Arctic declined by 7.8 percent each decade. If these trends continue, late-summer sea ice could disappear from the Arctic as early as early as 2030. Due to its light color, Arctic sea ice reflects most of the sunlight that reaches it back into space. In contrast, dark ocean water absorbs most of the sunlight. As sea ice continues melting, it can cause further warming, leading to more ice melt and reinforcing the melting cycle. As summer melt increases, wintertime recovery becomes more difficult. The animal most vulnerable to sea ice melt is the species at the top of the Arctic food chain, the polar bear, which hunts primarily on the sea ice. Penguins in the Antarctic are also affected by the disappearance of sea ice. The shrinkage of the Arctic ice will not affect sea level, however, since the Arctic ice cap is a sheet of ice "floating" in the water, much like ice cubes in a glass of water. If the ice cubes melt, they do not increase the level of water in the glass. In contrast, Greenland and Antarctica consist of large masses of ice resting on top of solid land, and melting