Interesting article, though I wonder why they didn't mention the Fram -- Nansen's ship that WAS designed to resist the crushing ice, and DID survive a trip across the northern seas purposely trapped in the crushing ice (but just missing the north pole)... If my memory serves, Shackleton knew about Nansen, and even talk with him before his (Shackleton's) expedition. shrug

In "South", Shackleton writes in detail about how the sinking occurred.

The ship up until that point had been firmly held in the ice and so was being compressed equally in all directions, and was built for this and was fine.

The sinking occurred because the ice had melted in the immediate vicinity of the ship (caused by the ship itself, I think), and then the ice resumed contact with the ship but not as before - contact was now at two or three points, such that the ship was now being bent by the ice.

Imagine you have a long thin twig in your hand and you hold it at each end and bend it upwards, in the middle.

That was not okay, and that sank the ship.

There's a diagram in the book, Shackleton penned it to illustrate the situation.

I skimmed the AT article, it mentions nothing of this, but writes at length about the ship not really being designed for Arctic work, etc. The article to me seems incorrect.