I posted this to /r/dwarffortress too.
I found that there was little information from people who had been to the World's Edge or Far North, so decided to do some exploration.
So, I was travelling north, in the snowy, frozen northern ocean, coming occaisionally across the odd crab or sea otter, when I see the following: a flock of Albatross heading the same direction as me. Cool. And then in front of me I see a looming [Ice Wall.](
http://imgur.com/I94FY&IFibA&B1UL2&SMvbk&QsEje&cT0Bn&BSoW8#4) 1 z level high. ice on the top of it. I'd just like to also say that by now the game has slowed noticeably.
"So". I think. "Is this It?" the albatross simply fly over it. An odd thing for the END OF THE WORLD to allow. So I follow the wall to the east and come to [This](
http://i.imgur.com/I94FY.png?1). (Yes, there are penguins there. First Arctic animals). A corner. It's NOT the edge of the world. Interesting. So I advance Northward. I reach a corner on the other side of the ice wall, making a [ shape of ice in my vision. I am barely past that when [THE SPACE BEHIND ME IS REPLACED WITH AN ICE WALL!](
http://imgur.com/I94FY&IFibA&B1UL2&SMvbk&QsEje&cT0Bn&BSoW8#3). And there's mist. That means this isn't some strange glitch from being too far north like the Far Lands in Minecaft. The game DID THIS. Also, I'm trapped. Great.
Northwards we continue, until I happen upon another [Ice Wall](
http://i.imgur.com/QsEje.png?1). Eastwards I continue until I see another [corner.](
http://i.imgur.com/cT0Bn.png?1) Suddenly the land to the west of me [freezes again.](
http://imgur.com/I94FY&IFibA&B1UL2&SMvbk&QsEje&cT0Bn&BSoW8#6)
By now the game has slowed to unplayable levels. I save the game and move it to my more powerful computer.
Continuing the game; I move North, until I find [another wall ahead of me.](
http://i.imgur.com/2Dev7.jpg?1). And then [East.](
http://i.imgur.com/5YUtR.jpg?1) from here I can see mist coming from one of the walls. (left side of image) I look up (right side of image) and see above the first ice wall, there is another. Like an Ice Mountain.
I carry on East until [a third corner cuts me off](
http://i.imgur.com/LDexn.jpg?1). South it is. When I find the southern wall, I think that I have been boxed in, [but I find I am not](
http://imgur.com/2Dev7&5YUtR&LDexn&2eJ7s&X5hZI&Kq4IE&z1nek&vvUcV&sIGbY&Acu0g&CKxGd&hESbE&yoaNL&eG18v&zgXQ7&c0ljz&UksSv&k9LIV&6X2XP&ytLSc&wm5TA&Py0kr&ovmU3&i1gOH&9UHbl&kCBWi&RZdaa&2mQrh&Sf5pT&qC61N&rOhwR&DDp5q&HQnVw#4). Hey. [A Leopard Seal](
http://imgur.com/2Dev7&5YUtR&LDexn&2eJ7s&X5hZI&Kq4IE&z1nek&vvUcV&sIGbY&Acu0g&CKxGd&hESbE&yoaNL&eG18v&zgXQ7&c0ljz&UksSv&k9LIV&6X2XP&ytLSc&wm5TA&Py0kr&ovmU3&i1gOH&9UHbl&kCBWi&RZdaa&2mQrh&Sf5pT&qC61N&rOhwR&DDp5q&HQnVw#5). I find the wiki has little to say about them, so If I can hunt it and kill it, I can find out. Then again, it could kill me. SCIENCE!. [Turns out I was cut off.](
http://i.imgur.com/zgXQ7.jpg)
I chase the Leopard seal back north, when the Ice [freezes my space smaller.](
http://i.imgur.com/c0ljz.jpg).
Suddenly, I see that a crack has appeared in the Ice! It is only A pile of snow over open space, however I go down it for science. It went down to the ocean below. [I floundered and drowned, despite adequate swimming.](
http://i.imgur.com/6X2XP.jpg)
I am usually against using Task Manager to end a game and carrying on the last save, but this is Science. And so, for the umpteenth time in my life I do the dishonourable thing in the quest for knowledge and reload the save; chasing the Leopard Seal.
Armok must have known I dodged death, because suddenly [the ground I stand upon becomes an Ice Wall and I am encased in it](
http://i.imgur.com/ytLSc.jpg), killing me (and probably the seal).
**TLDR/CONCLUSION:**
I consider the expedition to be a moderate success, as I learnt the following :
* The North has Strange Moving Ice Walls, comparable to Fast Glaciers. They are 1 Z-Level High and capable of stacking. They are a danger and capable of encasing Dwarves in ice.
* A sea exists under Polar Ices. There is no air pocket and drowning is inevitable.
* The Arctic KILLS your framerate.
* Leopard Seals are Faster than Expected.
More research is required. More Expeditions to be conducted and perhaps a fortress constructed at the World's Edge.