Researchers say Arctic sea ice still at risk despite cold winter

Using the latest satellite observations, NASA researchers and others report 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.

On March 18 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 50-60 percent of the Arctic, this year it covers less than 30 percent. 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 six percent.

According to Walt Meier of the National Snow and Ice Data Center at the University of Colorado, Boulder, as ice ages it continues to grow and thicken, so that older ice is generally also thicker ice. This winter the ice cover is much thinner overall and thus in a more vulnerable state heading into the summer melt season. NASA’s ICESat satellite has contributed to understanding of the changes in ice thickness. To get a better understanding of the behavior of sea ice, NASA is planning a follow-on satellite mission, ICESat II, to launch in 2015.