The strategic Bering Strait between Russia and the United States usually is plugged with a thick cork of sea ice in December, keeping most ships from sailing between the Arctic and northern Pacific oceans.
But not this year.
Following an extraordinary spring and summer of warm Arctic temperatures, and the shriveling of Arctic sea ice to its second lowest extent on record, the strait remained mostly ice-free into early December.
Taking advantage of the situation, two gargantuan liquified natural gas tankers — each measuring three football fields long — passed through the Bering Strait early in the month, one heading for ports in East Asia, and the other returning.
"This would have been utterly unthinkable even 10 years ago,” says Rick Thoman, an Arctic climate specialist at the University of Alaska Fairbanks.