First opening dates of CAA allowing export of small volume (but significant percentage) of dwindling thickest Arctic Ocean ice? Usually later in season and very weather dependent. In addition to Jim H's excellent coverage:
-- a favorite late season animatiion from 2016
-- all-time favorite NOAA/NSIDC sea ice motion video 1990-2016 which only shows CAA export by implication.
--'garlic press' history: first use seems to be 08 Sep 16
http://forum.arctic-sea-ice.net/index.php/topic,1493.msg89335.html#msg89335-- nuanced analysis of start dates from NW passage forum
The 2016 melting season 08 Sep 16 #4701 on: September 08, 2016
Northwest Passage thread #195 on: August 01, 2016
2012
Southern NW route: August 9th
Middle NW route: July 31st
Northern NW route: August 27th
Northern route: August 4th
2013
Southern NW route: August 22nd
Middle NW route: Does not open
Northern NW route: Does not open
Northern route: August 29th
2014
Southern NW route: August 30th
Middle NW route: Questionably around September 14th
Northern NW route: Does not open
Northern route: August 7th
2015
Southern NW route: August 13th (taking a ridiculous maze like path around the ice though)
Middle NW route: September 8th
Northern NW route: September 8th
Northern route: July 31st