But Walter Meier of the National Snow and Ice Data Center at the University of Colorado in Boulder cautioned that the re-growth of seasonal ice does not necessarily mean a reversal in the warming trend that saw a record melt of Arctic ice last summer.
“It is seasonal ice, thin, vulnerable ... which could melt very easily,” Meier told reporters.
The polar ice cap consists of seasonal ice that expands and shrinks between summers and winters, and perennial ice, which had persisted for hundreds or thousands of years until the recent record warmth of summer melted vast areas of it.
According to microwave satellite data processed by NASA, perennial ice used to cover 50 to 60 percent of the Arctic. This year, it covers less than 30 percent.
Very old ice that has remained in the Arctic for at least six years declined from over 20 percent coverage during the latter half of the 1980s to just 6 percent this year.
