Figure 1. August 22, 2007 sea ice concentration showing the open Northwest Passage (red) and routes for the Northeast Passage (green), Image Credit: modified from NASA's Earth Observatory and NSIDC.

Long before the Panama and Suez Canals made commercial trading between the Atlantic and Pacific Oceans economically feasible, ships made the long and perilous trip around the African and South America continents. Explorers, traders, and world leaders looking for faster and less dangerous shipping routes to far-away areas of the world have long eyed two routes through the ice-choked Arctic Ocean--the fabled Northwest Passage, through the cold Arctic waters north of Canada, and the Northeast Passage, extending along the northern coast of Russia. The first recorded attempt to find and sail the Northwest Passage was in 1497, and ended in failure. The thick ice choking the waterways thwarted all attempts at passage for the next four centuries. Finally, in 1905, Roald Amundsen completed the first successful navigation of the Northwest Passage. It took his ship two-and-a-half years to navigate through narrow passages of open water, and his ship spent two cold, dark winters locked in the ice during the feat. More recently, icebreakers and ice-strengthened ships have on occasion battered their way through the ice-blocked route.

From west to east the Northwest Passage (indicated in red on the map) runs through the Bering Strait, Chukchi Sea, Beaufort Sea, and then through the waterways of the Canadian Arctic Archipelago in the Arctic Ocean. There are five to seven different routes through the archipelago, including the McClure Strait, Dease Strait, and the Prince of Wales Strait, not all of which are navigable by ships of certain sizes due to the shallow depths of the waterways in addition to the obstacles posed by the large amounts of pack ice that characterize the entire route. The passage then goes through Baffin Bay and the Davis Strait into the Atlantic Ocean. The Northeast Passage (indicated in green on the map), now called the Northern Sea Route, winds from Murmansk on the Kola Peninsula in the west past Petropavlovsk in Kamchatka, Magadan, Vanino, and Nakhodka to Vladivostok on Russia's Pacific seaboard.

Following either of the routes would necessitate navigating through the Arctic Ocean for much of their lengths, dodging icebergs and sea ice floes that threatened to sink or stop a ship dead in its path. However, the payoff, and therefore temptation, of an established commercially navigable route is large. In comparison to the route through the Panama Canal, the transportation of goods through the Northwest Passage would shave off approximately 4000 km of the voyage from Europe to the Far East substantial savings in time and money.³

Both in Canada and in Russia, there are ports along the routes that remain ice-free all year, or at least all summer. However, even at the end of the summer, sea ice usually is still blanketing the areas through which ships would need to go, making both of the Northern routes impassable and unviable as commercial trade routes. The year 1906 marked the first successful expedition of the entire length of the Northwest Passage, but since that time, only ice-fortified ships have been able to travel the route.

Times are changing. In 2001, the Bering Strait, a key portion of both the Northwest and Northeast Passages, was completely ice free. This was followed in 2005 by record-breaking sea-ice melt in the Arctic, leading to the first ever recorded opening of the Northeast Passage. The fabled Northwest Passage remained closed in 2005. Arctic ice recovered a bit in 2006, and both passages remained closed. But the unprecedented melting during the summer of 2007 saw the Northwest Passage become ice-free and navigable along its entire length without the need for an icebreaker as of August 14, 2007. The sailboat Cloud Nine took advantage of the conditions, and sailed the entire length of the Passage. Remarkably, the Northwest Passage remained ice-free for 36 days, finally re-freezing over a small section on September 19. The Northeast Passage was blocked by a narrow strip of ice all summer. However, this strip of ice thinned to just 30% coverage on September 25 and 26, making the Northeast Passage passable for ordinary ships on those days.

We can be sure the Northwest Passage was never open from 1900 on, as we have detailed ice edge records from ships (Walsh and Chapman, 2001). It is very unlikely the Passage was open between 1497 and 1900, since this spanned a cold period in the northern latitudes known as "The Little Ice Age". Ships periodically attempted the Passage and were foiled during this period, and the native Inuit people have no historical tales of the Passage being navigable at any time in the past.

Figure 2.Sea ice along the Northeast Passage in June and July of 2007, Image Credit: NASA Earth Observatory

The Northwest passage may have been open at some period during the Medieval Warm Period, between 1000 and 1300 AD. A better candidate for the last previous opening was the period 5,000-7,000 years ago, when the Earth's orbital variations brought more sunlight to the Arctic in summer than at present. Prior to that, the next likely time was during the last inter-glacial period, 120,000 years ago. Arctic temperatures then were 2-3 degrees Centigrade higher than present-day temperatures, and sea levels were 4-6 meters higher. It is possible we'll know better soon. A new technique that examines organic compounds left behind in Arctic sediments by diatoms that live in sea ice give hope that a detailed record of sea ice extent extending back to the end of the Ice Age 12,000 years ago may be possible (Belt et al., 2007). The researchers are studying sediments along the Northwest Passage in hopes of being able to determine when the Passage was last open.

Notes:
¹ "Sir Robert McClure was credited with the discovery of the Northwest Passage in 1851 when he looked across McClure Strait from Banks Island and viewed Melville Island. However, this strait was not navigable to ships at that time, and the only usable route linking the entrances of Lancaster Strait and Dolphin and Union Strait was discovered by John Rae in 1854."http://en.wikipedia.org/wiki/Northwest_Passage
² http://en.wikipedia.org/wiki/Northern_Sea_Route
³ "If navigable, that would cut 11,000 kilometers off the Europe-to-Asia route through the Panama Canal and 19,000 kilometers off the trip around Cape Horn for supertankers unable to squeeze through the canal." Kerr, Richard A. A Warmer Arctic Means Change for All. Science 30 August 2002: Vol. 297. no. 5586, pp. 1490 - 1493, http://www.sciencemag.org/cgi/content/full/sci;297/5586/1490.
⁴ http://www.nsidc.org/news/press/2007_seaiceminimum/20070810_index.html#top

References

Belt, S.T., G. Masse, S.J. Rowland, M. Poulin, C. Michel, and B. LeBlanc, "A novel chemical fossil of palaeo sea ice: IP25", Organic Geochemistry, Volume 38, Issue 1, January 2007, Pages 16-27.

Walsh, J.E and W.L.Chapman, 2001, "Twentieth-century sea ice variations from observational data", Annals of Glaciology, 33, Number 1, January 2001 , pp. 444-448.

Further Reading

http://en.wikipedia.org/wiki/Northwest_Passage
http://en.wikipedia.org/wiki/Northern_Sea_Route
http://www.nsidc.org/
http://earthobservatory.nasa.gov/