Climate change might open up Northwest Passage to shipping by the middle of the century.

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Differences in transit routes for two kinds of vessels (red and blue) enabled by shrinking Arctic ice levels and opening of the Northwest Passage by 2050 (Image: Smith and Stephenson, PNAS, Early Edition)

Investigating what is sometimes seen as one of the more favorable effects of climate change, a pair of scientists from UCLA has done a careful analysis of the melting of Arctic sea ice and concluded that it could lead to ships traversing the ice-free Northwest Passage (NWP) by 2050. It would also lead to much shorter transit times through the existing North Sea Passage (NSR). These developments may greatly reduce the time and cost of shipping but would also lead to unforeseen economic and geopolitical complications.

The study looked at estimates of sea ice melting ? gathered from both models and observations including satellite measurements ? and then used seven different climate models to calculate the decrease in sea ice and its impact on shipping over the next few decades. The models are General Circulation Models (GCMs) that have been routinely used by the IPCC to estimate diverse impacts of climate change, including changing ice and sea levels. From the IPCC predictions the authors used two different climate forcings ? measures of global temperature changes induced by human and natural activities ? to calculate the distribution, thickness and changes in sea ice in the Northwest and North Sea passages. The goal of the study was to broadly estimate how the opening up of the Northwest Passage would affect the transit of two major classes of shipping vessels in the peak month of September, when sea ice levels are at their lowest. The relevant ships are the so-called PC6 and open water (OW) vessels which are designed to navigate ares with low to moderate ice density. The report asks only for the optimal route for these vessels in terms of transit time since other factors like economics and legal issues are difficult to take into account.

The researchers started by testing their models by hind-casting the distribution of ice for the period 1979 ? 2005. Once the models were reliably benchmarked for this data set, they were then asked to predict the accessibility of the NWP and the NSR during the next few decades. The results pointed to a significant opening up of transit routes to both PC6 and OW vessels.

For the NSR, sea-ice restricted the probability of shipping during the 1979-2005 period to just 40%. This probability rises to more than 95% for the period 2040-2060.?The effects on the NWP are even more striking. The opening up of unprecedented shipping routes by 2040 or so is plainly evident in the models. Figures C and D illustrated above display the significant differences for transit times for PC6 (red) and open water (blue) vessels over the next half-century. The line weights indicate number of successful transits. As the authors put it:

?The emergence of a robust PC6 corridor directly over the North Pole indicates that, in either scenario, sea ice will become sufficiently thin (e.g., <1.2-m thick at 100% ice concentration) and/or diffuse such that a critical technical threshold is surpassed, and the shortest great circle route thus becomes feasible, for ships with moderate ice-breaking capability?the Northwest Passage (NWP), arguably the most historically famed of potential shipping routes through the Arctic, has the lowest navigation potential both historically and at present but opens substantially by 2040?2059.?

The models find that for voyages from Eastern North America, the NWP might be the favored route for shipping by mid-century, essentially allowing transport 100% of the time during the peak season. The report concludes that

?Put simply, by midcentury, September sea ice conditions have changed sufficiently in the NWP such that trans-Arctic shipping to/from North America can commonly capitalize on the ?30% geographic distance savings that this route offers over the NSR.?

These significant savings would undoubtedly provide a great incentive for several countries to take advantage of the newly opened shipping corridor. The authors conclude by reasonably speculating that international trade and economic agreements will have to be significantly revised to take this new situation into account. In addition the opening up of what has historically been a most attractive shipping route would lead to the unforeseen geopolitical consequences which inevitably arise from such large-scale planetary changes.

Source: http://rss.sciam.com/click.phdo?i=055258d0215443b61f2a2c9fd4ccc75e

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