Atmosphere Journal Entry

Thickest Arctic Ice is Melting (March 31, 2008)

Arctic sea ice has steadily melted away over the past three decades. Last summer, there was less ice surrounding the North Pole than had ever been observed before. Now perennial ice, the thickest and oldest sea ice, is melting too.

Perennial ice doesn't melt from year to year. Some of it is hundreds or thousands of years old. Satellite data shows there's been a huge drop in this kind of ice.

Just twenty years ago, perennial ice covered more than fifty percent of the Arcitc Ocean. Now, it covers only thirty percent. Overall, perennial ice covered more than twenty percent of the Arctic as late as the mid-1980s. Measurements this past winter show it now covers only six percent of the Arctic.

Global warming is blamed for the melting ice. But the change isn't a direct result of rising temperatures in the atmosphere. The warming makes ocean water warmer and shifts wind patterns that affect the Arctic. Changes in the wind pattern known as the Arctic Oscillation are pushing icebergs further to the south. Eventually, the icebergs may drift even more to the south, past Greenland and into the Atlantic.