The CCGS Amundsen makes light work of unexpectedly thin ice (Image: Paul Nicklen/National Geographic/Getty)

The ice may not retreat as much as feared this year, but what remains may be more rotten than robust

LAST September, David Barber was on board the Canadian icebreaker CCGS Amundsen (pictured), heading into the Beaufort Sea, north of Alaska. He was part of a team investigating ice conditions in autumn, the time when Arctic sea ice shrinks to its smallest extent before starting to grow again as winter sets in.

Barber, an environmental scientist at the University of Manitoba in Winnipeg, Canada, went to sleep one night at midnight, just before the ship was due to reach a region of very thick sea ice. The Amundsen is only capable of breaking solid ice about a metre thick, so according to the ice forecasts for ships, the region should have been impassable.

Yet when Barber woke up early the next morning, the ship was still cruising along almost as fast as usual. Either someone had made a mistake and the ship was headed for catastrophe, or there was something very wrong with the ice, he thought, as he rushed to the bridge in his pyjamas.

On the surface, the situation in the Arctic looks dramatic enough. In September 2007, the total extent of sea with surface ice shrank further than ever recorded before – to nearly 40 per cent below the long-term average. This low has yet to be surpassed. But the extent of sea ice is not all that matters, as Barber found. Look deeper and there are even more dramatic changes. This is …