Mar 9, 2012; 10:32 AM ET
A new NASA study has found that the oldest, thickest sea ice in the Arctic region has been disappearing at a faster rate than younger, thinner sea ice.
Losing more of the thicker sea ice makes the entire northern sea ice cap much more vulnerable to an overall, accelerated decline.
According to the study, which was led by NASA's Joey Comiso, the area covered by multi-year ice has been shrinking by -17.2 percent per decade.
The two NASA images below are quite striking. The first image shows the sea ice coverage from Nov-Jan 1980. The thicker, multi-year ice can be seen as bright white, while the average, thinner ice closer to the edges is either milky white or light blue.
1980
2012
By Jan 2012, you can see the dramatic reduction in the thicker, multi-year ice.
Excerpts from the NASA Earth Observatory article......
The thickest "multi-year" ice survives through two or more summers, while young, seasonal ice forms over a winter and typically melts just as quickly as it formed. Scientists also describe a third category: "perennial" ice is all ice cover that has survived at least one summer. All multi-year ice is perennial ice, but not all perennial ice is multi-year ice.
Comiso found that perennial ice extent has been 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 multiyear ice is declining faster than the perennial ice that surrounds it.
Key quote from Comiso via NASA EO......
"The Arctic sea ice cover is getting thinner because it's rapidly losing its thick component," Comiso said. "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 multi-year sea ice to grow thick enough again to be able to survive the summer melt season and reverse the trend."
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