Tuesday, March 18, 2008

70% of Arctic ice is new - and unstable

source: http://www.newscientist.com/blog/environment/2008/03/70-of-arctic-ice-is-new-and-unstable.html

You may remember the hoo-ha about Arctic summer ice reaching an all-time low in September last year. We're now in the month when Arctic ice is normally at its maximum and NASA has just given an update on how things are going.

The big question is can the Arctic recover from last year's record low? The answer looks likely to be "no", and the key lies in the picture above.

You're looking down on the North pole. The figure to the left shows the average winter ice extent between 1985 and 2000; that to the right is the situation now, in February 2008. The colours are the big thing - they show how old the ice is, from six years and older in purple to less than one year in red.

The take-home message is that more than 70% of the ice in the Arctic has "grown" since last summer. That's a scarily low number - usually only half is "new growth".

"Ice can stay around for up to 10 years," says Walter Meier of the National Snow and Ice Data Center at the University of Colorado, US. "Old ice is really thick, tough as nails, and very resistant to short term melting." New ice, that red stuff in the figure above, is not thick, not tough - and not resistant to melting.

This winter has been colder than the norm, and this means the extent of winter ice is greater than in recent years. But Meier and his colleagues say it will take more than one cold winter to compensate for the damage caused b! y last s ummer's warm weather.

They say it would take a string of consecutive cold winters - and with Arctic temperatures rising faster than temperatures anywhere else on the planet, that looks an unlikely prospect.

Catherine Brahic, online environment reporter

No comments: