Comments 1 to 8:

1. citizenschallenge at 14:33 PM on 6 October, 2011
   WOW First class post! Thank you for that information
2. Camburn at 12:55 PM on 12 February, 2012
   JMurphy: The Voyage of 1944 was not quite as difficult as you maintain. Capt Larsen was a skilled Captain. At times there was heavy ice, at times there was no ice to be seen. To have accomplished this without the benifit of satillite images is really a feat in and off itself.
3. JMurphy at 01:13 AM on 13 February, 2012
   Camburn, I have never called into question the skills of Capt. Larsen (in fact I praise him and his crew), but his own words (as given above) speak volumes : ...“It was really the only fine day we had during the entire passage...” (2) “...season was the worst in years.” (1) (2) Read the references given if you can.
4. Tom Curtis at 10:58 AM on 14 February, 2012
   Camburn elsewhere maintains that the N-W Passage was significantly warmer than current for long periods of the Holocene, citing as evidence Bow Head whale skeletons. My understanding is that bow head whale skeletons can be found across the length of the North West Passage during a period the preceding the Holocene Climactic Optimum:

   "The distribution and radiocarbon ages of whale remains indicate that during at least one interval of the Holocene, Bering Sea and Davis Strait bowheads could intermingle, (Figure 1b). The Bering Sea bowhead was the first to reach the CAA about 10,000 carbon-14 (14 C) years ago (11,450 calendar years B.P.). Bowheads entered via the Beaufort Sea about 1000 years after submergence of the Bering Strait, and they ranged up to the fronts of receding continental ice sheets [Dyke et al., 1996; Dyke and Savelle, 2001]. Until about 9500 14 C years B.P. (10,700 calendar years B.P.), by which time the Davis Strait bowhead ranged into the eastern Northwest Passage, the Bering Sea and Davis Strait stocks were separated by a glacier ice barrier. With dissipation of this barrier, the two stocks were able to intermingle, ranging well beyond historical limits. About 8000 14 C years B.P. (8900 calendar years B.P.), the Bering Sea and Davis Strait stocks were separated, as they are today. Thus, a year-round sea ice barrier must have become established at that time in the central part of the Northwest Passage."

   (Fisher et al, 2006, my emphasis) In other words the NW Passage was open only for 1,800 year interval ending approx 9,000 years ago and there has been no skeletal evidence since for the intermingling of Atlantic and Pacific Bowheads. That strongly suggests any opening of the straits since then has been brief, and intermittent at best. For what it is worth, genetic evidence suggests the Bering Strait Variety of Bowhead are more closely related to the Hudson Bay stock than to the Davis Strait stock. It also indicates genetic separation of Hudson Bay and Bering Strait stock for at least 8,500 years; which is consistent with a forced separation by the closure of the North West Passage since before the Holocene Climactic Optimum. It should be noted that Atlantic and Pacific Bowheads have once again started intermingling. This evidence strongly suggests that the North West Passage and Canadian Archipelago was warmer than at present approx 10 thousand years ago at the last peak of northern summer insolation (red curve and figures): However, it also strongly suggests it has not been warm enough in that region to maintain open waters since then, even though the Earth itself was warmer due to the gradually melting ice sheets. Unless you have specific evidence of Bow Head populations intermingling in the North West Passage post 7,000 BC, you should stop using this evidence as though it suggested intervals of the passage being open throughout the Holocene. You frequently make that suggestion, but I see no evidence that supports it. (Note: cross posted from here as I believe this to be the most germane place for this discussion.)
5. Camburn at 11:41 AM on 14 February, 2012
   Tom: I wasn't talking about the NW Passage, but that's ok. Bow head whale proxy data: Calgary Research Bowhead fossils Please note that the above paper mentions a period of low ice and expansion of bowhead whale domain approx 1,000 YBP which correlates well with the pollin proxy data of 2,000 years of Climate Reconstruction.
6. MRoscio at 19:35 PM on 4 September, 2015

   The first commercial ship to complete the Northwest Passage, in both senses, in the same year, was the US supertanker Manhattan in 1969.

   The second one, as far as I know, was the drilling ship Canmar Explorer II in 1976.

7. MRoscio at 19:38 PM on 4 September, 2015

   I obviously meant "in both directions", East-to-West then West-to-East.  Apologies.

8. Tom Curtis at 20:27 PM on 4 September, 2015

   MRoscio @6 & 7, the Manhattan was accompanied by an icebreaker, the USCGC Northwind, on its westward passage, and by another icebreaker, the USCGC Staten Island on its eastward passage.  At some unspecified stage, it also had additional assistance by the CCGS Louis S. St-Laurent.  This despite having been modified to itself be an icebreaker.   Likewise, the Canmar Explorer II was also accompanied by an icebreaker, the CCGS Louis S. St-Laurent.

   Given that multiple commercial ships and hobby craft transit the Northwest Passage every year now, without icebreaker assistance, I am not sure what your point is. 

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