We often see maps showing the diminishing extent of sea ice in the Arctic. The issue has big consequences for global warming as well as geopolitical. Ice free areas in the summer mean the Arctic Circle is being ventured more and more by commercial and private entities (oil tankers, fishermen, maritime traders and even cruise ships). And governments are looking at the possibilities for future oil and gas exploitation.

Although the maps we typically see show a decrease in the overall extent of sea ice, the interesting story appears when we look at the age of that ice. We did the graphic below for the Fall 2018 issue of Foreign Policy magazine. The author spent time with the Norwegian Coast Guard, which is having trouble to respond to the emergency situations associated which the much higher activity in the area. The map shows how old is the ice that doesn’t melt. As the caption says

“… not all ice is created equal. It used to be that ice that had been around for more than five years was much slower to melt. These maps show the decline of ice aged 5 and up in September when ice extent is at its minimum. Older Arctic ice should be thicker and thus less likely to melt during the warm summer months. Younger ice breaks up more easily and allows more heat to escape from the ocean to the atmosphere, leading to higher ocean temperatures during the summer.”

So it’s the dramatic decrease in the extent of the older ice what is alarming, much more than the overall extent which is decreasing but doesn’t change that much from one year to the next. A series of simple and nifty maps unveils what is hidden below the surface.