The Northwest Passage--the legendary shipping route through ice-choked Canadian waters at the top of the world--melted free of ice last week, and is now open for navigation, according to satellite mosaics available from the National Snow and Ice Data Center and The University of Illinois Cryosphere Today. This summer marks the fourth consecutive year--and fourth time in recorded history--that the fabled passage has opened for navigation. Over the past four days, warm temperatures and southerly winds over Siberia have also led to intermittent opening of the Northeast Passage, the shipping route along the north coast of Russia through the Arctic Ocean. It is now possible to completely circumnavigate the Arctic Ocean in ice-free waters, and this will probably be the case for at least a month. This year marks the third consecutive year--and the third time in recorded history--that both the Northwest Passage and Northeast Passage have melted free, according to the National Snow and Ice Data Center. The Northeast Passage opened for the first time in recorded history in 2005, and the Northwest Passage in 2007. It now appears that the opening of one or both of these northern passages is the new norm, and business interests are taking note--commercial shipping in the Arctic is on the increase, and there is increasing interest in oil drilling. The great polar explorers of past centuries would be astounded at how the Arctic has changed in the 21st century.

 

 

 

Figure 4. Arctic sea ice extent image for August 24, 2010, as compiled by The University of Illinois Cryosphere Today. The northern route (Western Parry Channel) through the Northwest Passage was completely clear of ice, as was the Northeast Passage. The southern route through the Northwest Passage was still partially blocked.

What caused the opening of the Northwest and Northeast Passages?

The remarkable thinning of Arctic sea ice in recent years has left behind a very thin layer of mostly 1-year old ice in the Arctic, highly vulnerable to rapid melting. As I describe in detail in wunderground's sea ice page, this thinning was mostly due to natural wind pattern in the 1990s, much warmer than average ocean waters invading the Arctic from both the Pacific and Atlantic Oceans, very warm air temperatures, and deposition of black soot from fires used to clear agricultural land in Europe and air pollution originating in industrialized regions of the Northern Hemisphere. This year, Canada experienced its warmest winter in history, and record warm temperatures were observed during spring over the Western Canadian Arctic. Spring 2010 was the warmest in the region since 1948; some regions of the Western Canadian Arctic were more than 6°C (11°F) above average. These warm conditions helped break the ice up early in the Northwest Passage. Warm conditions continued this summer over both the Northwest and Northeast Passages, with temperatures averaging 1 - 2°C above average over the majority of the region. As observed in previous years, contributing to this year's melt was the presence of much warmer than average ocean waters invading the Arctic from both the Pacific and Atlantic Oceans, and the deposition of black soot on the ice, which absorbs sunlight and heats up the ice. Lack of sunshine and natural wind patterns this summer helped counteract the melting, though, compared to the record melt year of 2007. Still, 2010 is on track come in 2nd or 3rd place for the lowest summertime Arctic sea ice extent on record. The past six years have had the six lowest Arctic ice extents on record, and this summer's melting season took a huge toll on the amount of thick, multi-year old ice, according to the National Snow and Ice Data Center. Modeling results from the University of Washington Polar Science Center (Figure 5) suggest that the volume of Arctic sea ice is at a record low for this time of year. The loss of so much old, thick ice this year makes it increasing likely that Arctic sea ice will suffer a record retreat that surpasses 2007's, sometime in the next ten years. We are still on track to see the Arctic sea ice completely disappear in summer by 2030, as predicted by a number of Arctic sea ice experts.

 

 

Figure 5. Arctic sea ice volume as computed by the PIOMAS model of the University of Washington Polar Science Center.