THE ARCTIC CIRCLE, July 31: For much of the year, the Arctic appears as a crumpled white sheet of ice and snow before great chunks break off around the edges in spring, forming a sea of floes that gently dance across the frigid waters.
The floating ice slowly shrinks throughout summer until another winter season starts.
Because of global warming, more sea ice is being lost each summer than is being replenished in winters. Although sea ice is likely to continue forming each winter, it may be restricted to even higher latitudes.
Less sea ice coverage also means that less sunlight will be reflected off the surface of the ocean. The water will absorb more heat, further fueling global warming.
Sea ice forms when the top layer of water reaches freezing point, usually around the start of October. As temperatures continue to fall, this first-year ice grows downward until it is several feet thick. If the ice survives the following summer melt, it becomes second-year ice. Another cycle and it becomes multi-year ice — which is the toughest kind.
Sea ice plays an important role in the global climate system by cooling the surrounding water and air. It helps maintain ocean and atmospheric currents that affect weather that is characteristic for certain parts of the world, such as the comparatively mild temperatures found in western Europe.