Images from Europe’s Envisat satellite show that both the fabled Northwest Passage north of Canada and the Northeast Passage north of Russia have become ice-free.
This has allowed a succession of tankers to sail from Russia’s northern port of Murmansk, along the Siberian coast en route to Thailand.
The melt of polar sea ice earlier appeared to be poised to break the record maximum extent set in 2007.
But in recent weeks the coverage of open water has been running a narrow second behind 2007.
The actual maximum melt usually occurs about mid-September.
Graphic: National Snow and Ice Data Center