Using the latest satellite observations, NASA researchers and others reported on Tuesday that the Arctic is still on "thin ice" when it comes to the condition of sea ice cover in the region.
A colder-than-average winter in some regions of the Arctic this year has yielded an increase in the area of new sea ice, while the older sea ice that lasts for several years has continued to decline.
Arctic sea ice grows and declines seasonally. In March this year, instruments on some U.S. satellites showed the maximum sea ice extent slightly increased by 3.9 percent over that of the previous three years, but it is still below the long-term average by 2.2 percent.
Increases in ice extent occurred in areas where surface temperatures were colder than the historical averages. At the same time, the area of perennial ice decreased to an all-time minimum.
The scientists said they believe that the increased area of sea ice this winter is due to recent weather conditions, while the decline in perennial ice reflects the longer-term warming climate trend and is a result of increased melting during summer and greater movement of the older ice out of the Arctic.
Perennial sea ice is the long-lived, year-round layer of ice that remains even when the surrounding short-lived seasonal sea ice melts away in summer to its minimum extent.
It is this perennial sea ice, left over from the summer melt period, that has been rapidly declining from year to year, and that has gained the attention and research focus of scientists.
According to NASA-processed microwave data, whereas perennial ice used to cover 50 percent to 60 percent of the Arctic, it covers less than 30 percent this year. Very old ice that remains in the Arctic for at least six years comprised over 20 percent of the Arctic area in the mid to late 1980s, but this winter it decreased to just 6 percent.
Source:Xinhua
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