Sea ice is frozen ocean water. It forms, expands, and melts in the ocean. Typically, sea ice is covered with snow. Importantly, Arctic sea ice retains the regions cool and stabilizes global climate. A bright surface of sea ice reflects 80 percent of the striked sunlight back to the space. When sea ice melts in the summer, the ocean absorbs 90 percent of the sunlight. The oceans heat up and Arctic temperatures increase.
In September of each year, Arctic sea ice reaches it minimum and now declining at a rate of 13.4 percent per decade, relative to the 1981 to 2010 average. Temperature in the Arctic has increased at twice the rate as the rest of the globe, and the region is expected to increase an additional 8°C (14°F) in the 21st century. Winter temperature has increased more than summer temperature, which is a trend that is expected to continue. While some have suggested that these variations in temperature and associated sea ice melt is a natural cycle, recent research tells us that the Arctic was in a 2,000 year cooling trend before the 20th century and its influx of greenhouse gases.
Declining in arctic sheet with average September extent