Arctic sea ice variability and trends, 1979–2006

Analysis of Arctic sea ice extents derived from satellite passive‐microwave data for the 28 years 1979–2006 yields an overall negative trend of −45,100 ± 4,600 km 2 /a (−3.7 ± 0.4%/decade) in the yearly averages, with negative ice extent trends also occurring for each of the four seasons and each of the 12 months. For the yearly averages, the largest decreases occur in the Kara and Barents seas and the Arctic Ocean, with linear least squares slopes of −10,600 ± 2,800 km 2 /a (−7.4 ± 2.0%/decade) and −10,100 ± 2,200 km 2 /a (−1.5 ± 0.3%/decade), respectively, followed by Baffin Bay/Labrador Sea, with a slope of −8000 ± 2000 km 2 /a (−9.0 ± 2.3%/decade), the Greenland Sea, with a slope of −7000 ± 1400 km 2 /a (−9.3 ± 1.9%/decade), and Hudson Bay, with a slope of −4500 ± 900 km 2 /a (−5.3 ± 1.1%/decade). These are all statistically significant decreases at a 99% confidence level. The seas of Okhotsk and Japan also have a statistically significant ice decrease, although at a 95% confidence level, and the three remaining regions, the Bering Sea, Canadian Archipelago, and Gulf of St. Lawrence, have negative slopes that are not statistically significant. The 28‐year trends in ice areas for the Northern Hemisphere total are also statistically significant and negative in each season, each month, and for the yearly averages.