Plain sailing in the Arctic

The Northwest Passage is one of those names that conjure up romantic images of bearded explorers with a passion for cannibalism. The Victorian dream of taking a sailing ship through the Arctic to the North Pacific without all that tedious mucking about with South America took quite a few lives. Even with the construction of the Panama Canal, such a route would shave nearly 4000 kilometres off a trip between Europe to Asia. Yet at the end of summer, there’s traditionally been enough sea ice to keep shipping firms at bay. But this is all starting to change. Just this week the European Space Agency announced the first navigable route was open through the ice.

Bowhead whales
How unusual is this?

In 1906 the Norwegian, Roald Amundsen, managed to negotiate his way through the icebergs, and lived to tell the tale - but it took him two years. Essentially, permanent sea ice cover has made such a trip impossible for routine shipping. Working out what the ice did in the past, however, is easier said than done. There’s very little physical evidence of where it’s been; after all, it’s pretty much just frozen water. Fortunately, we can turn to nature. Each year, bowhead whales that live in the region follow the expansion and contraction of the sea ice front. As temperatures plummet through the winter, the whales move out as the sea ice increases in area, reaching most northern coastlines by March. But by September, summer heating causes the sea ice to retreat and so too do the whales. Canadian researcher Art Dyke has developed an ingenious approach to exploit this relationship: by dating fossil whalebones he can reconstruct what the sea ice did in the past. The results make sobering reading. The last time the Northwest Passage was open was 8900 years ago.

Worryingly, earlier this year Julienne Stroeve at the University of Colorado and colleagues looked in detail at historical losses of sea ice in the Arctic. Their results suggest that if we take the observational data over the past three decades, almost 60 percent of the lost sea ice can be explained by increasing greenhouse gas levels; far higher than anyone has suggested before. Not only this but they found that when computer models of changing sea ice have been run in the past, they all underestimated how much has been lost. Prophetically Stroeve warned that if this is right, it implies the Arctic is a lot more sensitive to increasing greenhouse gases levels. This week we’re seeing evidence of this; in 2007, melting ice has increased ten fold. The Arctic region looks like it’s on a fast track to conditions not seen for at least 8,900 years.

It is greenhouse gas forcing that’s driving the most recent bout of Arctic melting, and yet, perversely, media reports seem to be arguing there’s a plus side: vast reserves of previously inaccessible oil and gas will now be available for drilling. It doesn’t look like the penny has dropped in some quarters.


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