Sure, if you happen to already know where the Wedell Sea is or if you look it up it you can reasonably locate it, in which case adding the "north of Antarctica" part is superfluous. But if you don't already know where the Wedell Sea is, adding in the "north of Antarctica" part doesn't actually narrow it down any, which is why it's a funny thing to point out.

If they had wrote "just north of Antarctica" or "off the coast of Antarctica" or "near Antarctica", that would have narrowed it down significantly.

Now that I have thoroughly explained the joke, I imagine it's much funnier now.

I'm sure that "Mark "Three-Jabs" Newton" and the rest of us who found this funny were able to deduce from the context that is actually what the writer meant . That isn't what they actually wrote though so "sp3ctr4l" is not only incorrect in asserting that Mark has "poor reading comprehension", he is also wrong that 'reading the whole thing' would have clarified things and was extremely condescending about his incorrect statement at the same time, which makes him kind of an ass imo.

He was correct that Mark was "intentionally being a little shit" so 1 out of 3 wouldn't have been so bad if he weren't such a douche about it at the same time.