How thick is the human measured ice at the North Pole?

Question

http://www.globalpuzzle.net/wisdom-pieces/284/

Answer 1

The north polar ice cap is actually only three to four metres thick on average.  It can easily be sailed under in a nuclear-powered submarine (it has to be a nuclear sub, because a diesel engined one cannot use its snorkel or surface to allow its engines to breathe, and it's too far for a sub to travel safely under battery power)