Chuck Gould writes:

Attempts to navigate the NW Passage have been regularly thwarted since
the 16th century, with no navigable channel available. Cook,
Vancouver, etc all searched for the NW Passage....so it's not entirely
correct to say we didn't have any idea what when on up there prior to
the early 1970's. Thanks for letting me know it had been open briefly
in the 1940's, it will be interesting to see how long it remains open
this time.

Beginning in the 1970's we had satellite and other data that allowed
us to track the arctic ice coverage, so we can establish with fair
certainty thta in the last 35 years the NW Passage has not been
navigable during the summer months.

Two guys sailed through the NW passage in the mid 1980s on
a Hobie 18.

--
Martin Schöön "Problems worthy of attack
show their worth by hitting back."
Piet Hein