"We're talking about a future in which open-water vessels will, at least during some years, be able to navigate unescorted through the Arctic, which at the moment is inconceivable," said co-author Scott R. Stephenson, a Ph.D. candidate in the UCLA Department of Geography. The predictions, however, do not foresee shipping access beyond late summer. "This will never be a year-round operation," Smith stressed.
The researchers factored in two scenarios for climate change: one that assumed a 25 percent increase in global carbon emissions, and one that assumed an additional 10 percent increase in emissions. Changes in accessibility were similar under both scenarios.
The Arctic ice sheet is expected to thin enough to allow polar icebreakers navigate between the Pacific and Atlantic by making a straight pass over the North Pole. "Nobody's ever talked about shipping over the top of the North Pole," Smith said. "This is an entirely unexpected possibility."
The route directly over the North Pole is 20 percent shorter than today's most-trafficked Arctic shipping lane, the Northern Sea Route along the coast of Russia. Today, the Northwest Passage, which offers the most direct route between Asia and eastern Canada, is theoretically navigable only one out of seven years, but by mid-century, sea ice will melt in September to the point that it is accessible every other summer, on average.
The projections have implications for commercial and government planning for port construction, acquisition of natural resources and the establishment of lane jurisdiction.
The increasing viability of Arctic shipping puts increased pressure on the U.S. to ratify the United Nations Convention on the Law of the Sea. Some new shipping lanes would pass through waters over which the U.S. could make internationally accepted sovereignty claims if it ratified the treaty. Countries that claim sovereignty are able to lay down rules for the vessels that pass through their waters.
Canada, for example, has long maintained that the nearly impassable Northwest Passage falls under Canadian sovereignty, while the U.S. maintains it is an international strait. Increasing accessibility could bring the U.S. into dispute with its neighbor.