Ice flows in Baffin Bay above the Arctic Circle are seen from the Canadian Coast Guard icebreaker Louis S. St. Laurent on July 10, 2008. Jonathan Hayward/The Canadian Press/AP

The old Arctic ice serves as a 'bulwark' against further melting, even as newer ice melts and refreezes from year to year.

Scientists have warned of the melting of Arctic ice for years. As 2016 stands ready to be crowned the hottest year on record, the effects of that heat are being most acutely felt by the ice-bound regions at the northern pole of our planet.

Researchers at NASA have noted a new trend in the warming story in the extreme north. Not only is seasonal ice melting into the ocean, but the older ice that has remained constantly frozen, sometimes for decades, is also showing signs of significant thinning. The oldest ice in the Arctic has traditionally served as a line of defense against warming, protecting the northern ice cap's integrity through normal seasonal changes. But as the ocean continues to warm, so does the polar cap, leaving the future of the Arctic ice uncertain.

Thanks to decades of observing Arctic ice, scientists are beginning to piece together longer-term trends in the effect of climate change on older patches of ice. Using these observations, NASA scientists have created a new visualization of the ice cap shrinking and shifting with the seasons since 1984.

"What we’ve seen over the years is that the older ice is disappearing," said Walt Meier, a sea ice researcher at NASA’s Goddard Space Flight Center in a statement. "This older, thicker ice is like the bulwark of sea ice: a warm summer will melt all the young, thin ice away but it can’t completely get rid of the older ice. But this older ice is becoming weaker because there’s less of it and the remaining old ice is more broken up and thinner, so that bulwark is not as good as it used to be."

The team used passive microwave satellite images, weather data, and buoys to track the status of older ice. Sea ice that survives multiple melting seasons gets thicker with age, about 10 to 13 feet thick compared to 3 to 7 feet of thickness for seasonal ice during its first year. But tracking the overall trends in the status of the ice cap can be tricky.

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By Weston Williams

Source: The Christian Science Monitor