SENSibility 9: The Old Ice is Leaving Us

More news from the global “uh oh” file.

There is evidence that the old, thick ice of the arctic is melting away faster than previously thought. Ice that is more than two years old used to make up 60 percent of the arctic ice pack. Now, ice that is more than two years old makes up just 30 percent of the arctic ice pack. Yikes!

Ice Cover

This says a lot about the shrinking arctic ice pack. We know the area covered by the ice pack continues to decline. We know the rate of decline has accelerated in recent years. We know that this decline has implications for global warming, as less ice means less solar radiation reflected back into space, and more heat absorbed by the dark oceans (a change in albedo, for those earth and ocean science types). However, this declining amount of old ice tells us something new. Ice that has been around for a very long time is melting away. This old ice is considerable less saline than annual ice cover, so it is supposedly more resistant to annual melt. Not any more, it seems. New ice forms every year and melts. Old ice is melting and is not being replaced by “newer” old ice.

The next round of international negotiations on climate change are due to begin in 2009. Most estimates on arctic ice melt have predicted that the arctic will be ice free by the middle of this century. Now, one forecast suggests the arctic will be ice free by as early as 2013. We better get a move on.

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