Arctic sea ice continues decline as air temperatures rise
New satellite records monitored by a national team of collaborators show a four-year pattern of extremely low summer sea-ice coverage in the Arctic, which may be the result of warming temperatures and earlier spring melting. Since 2002, the satellite data have revealed unusually early springtime melting in areas north of Siberia and Alaska. In 2005, the trend expanded to include the entire Arctic ice pack, said Ted Scambos of the University of Colorado–Boulder's National Snow and Ice Data Center (NSIDC), which led the study. NASA and the University of Washington were also involved.
The research group used the satellite record—dating back to 1978—to determine that the 2005 spring and summer melting began about 17 days earlier than usual, a new record. Average air temperatures across most of the Arctic Ocean from January to August 2005 were between 2°C (3.6°F) and 3°C (5.4°F) warmer than average compared to the last 50 years, said the team.
The conditions were followed by the lowest sea-ice extent yet seen in the satellite data, a five-day mean average of about 5 million square kilometers (2 million square miles) on 10 September. This was lower than the average September sea-ice extent from 1978 to 2001 by about 20%.
With the exception of May 2005, every month since November 2004 has exhibited the lowest monthly average of sea-ice extent since satellite record-keeping began in the region. The trend of Arctic sea-ice decline documented by satellites is now about 8.4% per decade since the 1970s, the group reported.
Scientists believe the Arctic Oscillation, a major atmospheric circulation pattern that can push sea ice out of the Arctic, may have contributed to the sea-ice reduction in the mid-1990s, said Mark Serreze of NSIDC. However, that pattern has become less of an influence on the region since the late 1990s, and the sea ice has continued to decline. "Something has fundamentally changed here, and the best answer is warming," Serreze said.
The decline is likely to affect future temperatures in the Arctic. "Feedbacks in the system are starting to take hold," Scambos said. "The consecutive record-low extents make it pretty certain a long-term decline is under way."