As global warming melts sea ice across the Arctic, shipping routes once thought impossible — including directly over the North Pole — may open up by midcentury. But high costs may keep the new routes from being used right away.

2045 to 2060 2015 to 2030 Predicted fastest shipping routes through the Arctic Ice-breaking ships Pacific Ocean Regular ships Sea ice thickness North American routes North American routes 1m 0.5m 1m 0.5m Yokohama, Japan Atlantic Ocean European routes European routes As global warming continues, by 2030 routes over the North Pole could open for ice-breaking cargo ships capable of operating in ice up to four feet thick. By 2045 to 2060, the decline of Arctic sea ice under moderate warming could allow even ordinary cargo ships to journey directly over the North Pole. 0111001101101000011011110111010101110100011100110010000001101111011101010111010000100000001101110011010100110111 2045 to 2060 2015 to 2030 Predicted fastest shipping routes through the Arctic Ice-breaking ships Pacific Ocean Regular ships Sea ice thickness North American routes North American routes 1m 0.5m 1m 0.5m Yokohama, Japan Atlantic Ocean European routes European routes By 2045 to 2060, the decline of Arctic sea ice under moderate warming could allow even ordinary cargo ships to journey directly over the North Pole. As global warming continues, by 2030 routes over the North Pole could open for ice-breaking cargo ships capable of operating in ice up to four feet thick. 2045 to 2060 2015 to 2030 Predicted fastest shipping routes through the Arctic Ice-breaking ships Pacific Ocean Regular ships Sea ice thickness North American routes North American routes 1m 0.5m 1m 0.5m Yokohama, Japan Atlantic Ocean European routes European routes By 2045 to 2060, the decline of Arctic sea ice under moderate warming could allow even ordinary cargo ships to journey directly over the North Pole. As global warming continues, by 2030 routes over the North Pole could open for ice-breaking cargo ships capable of operating in ice up to four feet thick. Predicted fastest shipping routes through the Arctic Ice-breaking ships Regular ships 2015 to 2030 Pacific Ocean Sea ice thickness North American routes 1m 0.5m Yokohama, Japan Atlantic Ocean European routes As global warming continues, by 2030 routes over the North Pole could open for ice-breaking cargo ships capable of operating in ice up to four feet thick. 2045 to 2060 North American routes 1m 0.5m European routes By 2045 to 2060, the decline of Arctic sea ice under moderate warming could allow even ordinary cargo ships to journey directly over the North Pole. Predicted fastest shipping routes through the Arctic Ice-breaking ships Regular ships 2015 to 2030 Pacific Ocean Sea ice thickness North American routes 1m 0.5m Yokohama, Japan Atlantic Ocean European routes As global warming continues, by 2030 routes over the North Pole could open for ice-breaking cargo ships capable of operating in ice up to four feet thick. 2045 to 2060 1m North American routes 0.5m European routes By 2045 to 2060, the decline of Arctic sea ice under moderate warming could allow even ordinary cargo ships to journey directly over the North Pole.

The amount of sea ice covering the Arctic Ocean has declined sharply each decade since the 1980s, according to measurements taken each September when the ice is at its minimum. Older, thicker ice is disappearing as well. Scientists say global warming is largely responsible for the changes. Parts of the Arctic are warming twice as fast as elsewhere.

3,302 cubic miles 1,480 1,000 737 2015 to 2030 2045 to 2060 Volume of the Grand Canyon 1985 to 2000 average Arctic sea ice volume 3,302 cubic miles 1,480 1,000 737 1985 to 2000 average Arctic sea ice volume Volume of the Grand Canyon 2015 to 2030 2045 to 2060 3,302 cubic miles 1,480 1985 to 2000 average Arctic sea ice volume 2015 to 2030 1,000 737 2045 to 2060 Volume of the Grand Canyon Note: Future Arctic sea ice volume numbers are derived under a moderate-emissions scenario.

The changing conditions offer an opening to shipping companies. The Arctic is potentially a faster, more direct route between Asia and ports in Europe and eastern North America.

Currently there is relatively little cargo shipped through the region. Although shipping will increase over the next decade, especially as Russia develops oil and gas fields in Siberia, total Arctic cargo tonnage is expected to remain only a small fraction of the amount carried along southern routes through the Suez and Panama canals.

But with “middle of the road” warming — higher than the 2015 Paris accord target but lower than the most extreme climate change forecasts — more Arctic shipping routes could open, both for ordinary ships and those that are built to move through thicker ice. Even direct over-the-pole routes would potentially be navigable, at least during some part of the summer-fall shipping season.

“We know what is likely to happen to sea ice,” said Nathanael Melia, one of the researchers at the University of Reading in Britain who calculated how the routes might change as warming continues to the middle of the century. “It will reduce decade on decade, and open up vast swaths of the Arctic Ocean.”

As Arctic routes become more direct, voyage times could fall to less than three weeks in some cases, making Arctic shipping potentially more attractive than the southern routes in coming decades, Dr. Melia’s research shows.

2015 to 2030 Through 2030, routes connecting North America and Europe with Japan will take an average of just over 22 days. Number of routes Average 18 20 22 24 26 28 30 Number of days for voyage 2045 to 2060 By midcentury, more of these routes will have shorter journey times. Average 18 20 22 24 26 28 30 2015 to 2030 Through 2030, routes connecting North America and Europe with Japan will take an average of just over 22 days. Average Number of routes 18 20 22 24 26 28 30 Number of days for voyage 2045 to 2060 By midcentury, more of these routes will have shorter journey times. Average 18 20 22 24 26 28 30

Just because shippers could make greater use of Arctic routes does not necessarily mean they will. Ice conditions will still vary greatly from year to year, which would discourage shipping companies for which precise timing of shipments is crucial.