Thaindian News

GREENBELT, Maryland (BNO NEWS) — The oldest and thickest Arctic sea ice is disappearing at a faster rate than the younger and thinner ice at the edges of the Arctic Ocean’s floating ice cap, according to a new study revealed by NASA on Thursday.

The new research takes a closer look at multi-year Arctic sea ice and reveals that it is diminishing at a rate of 15.1 percent per decade. Scientists define multi-year Arctic sea ice as ice that has made it through at least two summers.

The study has reviewed multi-year ice “extent” - which includes all areas of the Arctic Ocean where multi-year ice covers at least 15 percent of the ocean surface - and how the ice has diminished with each passing winter over the last three decades.

When young ice that has formed over winter quickly melts again during the cyclical summer melt season, the thicker ice, known as multi-year ice, survives through the season.

However, Joey Comiso, senior scientist at NASA’s Goddard Space Flight Center and author of the study, which was recently published in Journal of Climate, noted that the rapid disappearance of older ice makes Arctic sea ice even more vulnerable to further decline in the summer.

Researchers also analyzed how the ice cap evolves through other measurements such as multi-year ice “area,” which discards areas of open water among ice floes and focuses exclusively on the regions of the Arctic Ocean that are completely covered by multi-year ice.

In the study, Comiso found that multi-year ice area is shrinking even faster than multi-year ice extent by 17.2 percent per decade.

“The average thickness of the Arctic sea ice cover is declining because it is rapidly losing its thick component, the multi-year ice,” said Comiso. “At the same time, the surface temperature in the Arctic is going up, which results in a shorter ice-forming season. It would take a persistent cold spell for most multi-year sea ice and other ice types to grow thick enough in the winter to survive the summer melt season and reverse the trend.”

In addition, Comiso found that the extent of perennial ice, ice that has survived at least one summer, is shrinking at a rate of 12.2 percent per decade, while its area is declining at a rate of 13.5 percent per decade. These numbers indicate that the thickest ice, multiyear-ice, is declining faster than the other perennial ice that surrounds it.

In the winter of 2008, multi-year sea ice hit its record minimum extent, when it was reduced to about 55 percent of its average extent since the late 1970s, when satellite measurements of the ice cap began.

Multi-year sea ice then recovered slightly in the three following years, ultimately reaching an extent 34 percent larger than in 2008, but it dipped again in winter of 2012, to its second lowest extent ever.