Sea ice flux through the Nares Strait is most active during the fall and early winter, ceases in mid- to late-winter after the formation of ice arches along the strait, and re-commences after breakup in summer. In 2007, ice arches failed to form. This resulted in the highest outflow of Arctic sea ice in the 13-year record between 1997 and 2009.
The Lincoln Sea area at the northern end of the Nares Strait was less fragmented at any time during 2007 than it is now, in April 2010.
April 30 2010 - MODIS/terra image of Nares Strait - Lincoln Sea area at 500 meter resolution.
Some of the early ice loss in Baffin Bay 2007 was due to a combination of wind and Coriolis effect which, rather than compacting ice against the west coast of Baffin Bay, drove it away from shore and dispersed it to the south.
The North West Passage, for many centuries found to be generally un-navigable, opened in August 2007. The loss of multi-year ice in the various passages between the islands appears to be irreversible. It is important to realise that prior to 1944, navigations of the passage had required overwintering: as the ice closed in on the ship it could proceed no further until - if luck prevailed - the next melt season freed the ship.
Roald Amundsen was the first person to sail the entire Passage from east to west. It took him three years to complete the journey. The first vessel to complete the voyage in both directions was the RCMP vessel St. Roch, pronounced 'rock'.
R.C.M.P. marine patrol vessel St. Roch in winter quarters at Herschel Island in the Beaufort Sea.
St. Roch is rightly famous as the first ship to completely circumnavigate North America; the second sailing vessel to complete a voyage through the Northwest Passage; the first ship to complete the Northwest Passage in the direction west to east, 1940-1942; first to complete the voyage in one season, 1944.
The first commercial ship sailed through the North West Passage November 28 20083.
The North West Passage has now been safely navigated by a number of leisure craft.
The ice in 2007 was still shorebound enough to block the North East Passage. In September 2009, the North East Passage was open to shipping for the first time ever without ice breakers4.
Once the Arctic is ice free, whether seasonally or annually, the local climate will be substantially warmer for longer. This will undoubtedly affect the permafrost, coastal erosion rates and the calving rates of Arctic glaciers. It might well bring forward a Greenland ice sheet tipping point.
Continued on next post.
 - Discussions of Arctic tipping points:
 - Large sea ice outflow into the Nares Strait in 2007, Kwok et al
 - http://www.cbc.ca/canada/north/story/2008/11/28/nwest-vessel.html
 - http://www.examiner.com/x-4648-Atlanta-Weather-Examiner~y2009m9d6-Arctic...
Melting Sea Ice Major Cause Of Arctic Warming - Study