Washington, Mar 1 (IANS): The oldest and thickest Arctic Sea ice is melting much faster than the younger and thinner ice at the edges of the Arctic Ocean's floating ice cap, an alarming new NASA study has revealed.

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

The rapid disappearance of older ice makes Arctic sea ice even more vulnerable to further decline in the summer, said Joey Comiso, senior scientist at NASA Goddard Space Flight Centre, Greenbelt, who authored the study, the Journal of Climate reported.

The new research takes a closer look at how multi-year ice, that has made it through at least two summers, has diminished with each passing winter over the last three decades, according to a university statement.

Multi-year ice "extent" -- which includes all areas of the Arctic Ocean which covers at least 15 percent of the ocean surface -- is diminishing at a rate of 15.1 percent per decade, the study found.

Sea ice area is always smaller than sea ice extent, and it gives scientists the information needed to estimate the total volume of ice in the Arctic Ocean.

Comiso found that multi-year ice area is shrinking even faster than multi-year ice extent, by 15.1 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. At the same time, the surface temperature in the Arctic is going up, which results in a shorter ice-forming season," Comiso said.

"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," Comiso concluded.