A project led by adventurer David Hempleman-Adams that aimed to sail the Arctic's North East and North West passages in a single season has completed its quest.
The yacht Northabout left Bristol, UK, in June and circled the North Pole in an anticlockwise direction.
Its exit from Canada's Lancaster Sound on Monday signalled the successful navigation of both sea routes.
Mr Adams initiated the project to highlight Arctic sea-ice decline.
For so long an impenetrable barrier for mariners, the NEP and NWP have increasingly opened up in recent years as temperatures in the polar north have warmed.
This week, Arctic sea-ice reached the second-lowest extent ever recorded by satellites - a fact "verified 'on the ground' (water). It's real. We've been there," the Polar Ocean Challenge project told the BBC.
Ice has been so minimal around the islands that make up Canada's northern polar region that Northabout was able to sweep through the NWP in just two weeks.
Monday also saw confirmation that the second ship lost in the Arctic by 19th Century explorer Sir John Franklin has been found.
The Guardian newspaper reports that HMS Terror was identified in "almost pristine condition" sitting at the bottom of Terror bay.
Franklin's other ship, HMS Erebus, was found two years ago.
The explorer's attempt to chart the NWP in the 1840s was undone by thick ice, and cost the lives of more than 120 men.
His expedition's disappearance became one of the great maritime mysteries as a succession of search and rescue missions failed to find any trace of the ships and their crew.
The 15m-long, aluminium-hulled Northabout is now heading to Greenland and expects to get to Upernavik late on Wednesday.
The yacht will then sail south, down the west coast of Greenland, dodging icebergs from the country’s great outlet glaciers, before reaching across the North Atlantic for the return to the UK.
It expects to arrive home in October.
"That will be the end of the second quest, which will be a circumnavigation of the North Pole in one summer season - which strengthens the point," the project said.
Scientists fully expect commercial traffic in the NEP and NWP to grow in the coming decades as the region continues to warm.
A recent study found that by mid-century the opportunities for non ice-strengthened vessels to transit the Arctic could double, even if strong measures were taken to tackle climate change.