maritime route along the northern coast of the Eurasian landmass, lying mainly off northern Russian Siberia. Early explorers of the area included Willem Barents and Olivier Brunel. Under the auspices of the Russian tsar Peter I the Great, Semyon Dezhnyov probably (1648) and Vitus Bering certainly (1728) sailed northward through the Bering Strait. Captain James Cook (Cook, James), however, was the first to see both sides of the strait (1778) and to demonstrate that Asia and North America are two separate continents. After many attempts the Northeast Passage was first traversed by the Swedish explorer Baron Adolf Erik Nordenskiöld in 1878–79. Since the late 1960s the passage has been kept open in the summer months by icebreakers, aided by aerial observations and radar and sonar.