Sea ice flowing through the Bering Strait in May 2000
Credit: NASA EarthObservatory
The Arctic replaced a fraction of its thick multi-year sea ice during the winter of 2005, possibly accelerating a trend that leaves the Far North pack thinner and ever more vulnerable to melt during the summer.
The new NASA study found that “only about four percent of the nearly 2.5 million square kilometers (965,000 square miles) of thin, seasonal ice that formed the previous winter survived the summer and replenished the perennial ice cover” — the smallest replenishment seen to date.
The results, reported this March in Geophyiscal Research Letters, build on another a NASA study released in fall 2006 that reported a 14-percent drop in multi-year ice between 2004 and 2005. Results after 2006 haven’t been analyzed yet.
Sea ice extent down in March 2007
“Recent studies indicate Arctic perennial ice is declining seven to 10 percent each decade,” explained Ron Kwok, with the lab in Pasadena, Calif. “Our study gives the first reliable estimates of how perennial ice replenishment varies each year at the end of summer. The amount of first-year ice that survives the summer directly influences how thick the ice cover will be at the start of the next melt season.”