DK Island is not seen at the exact same angle each time. Each image is very close to being the same, but the one in K. Rool's Keep seems to be tilted slightly. Here is a picture for reference, which I discuss below.
Since the back of DK Island is facing North, and Dixie went to the Southernmost part of DK Island (which is near Kongo Jungle) and swam to the NK, we can assume that the Northern Kremisphere is actually in front and to the left (southwest) of Krocodile Isle. So both DK Island and Krocodile Isle are farther North than the Northern Kremisphere... that's a really strange conclusion to come to, unless of course the Northern Kremisphere is the main continent in that hemisphere and they just named the continent after the hemisphere it lies in. This also explains why the NK isn't visible in the distance behind DKI.
Also, I vaguely remember something like "... a whole new continent! ..." being written in the Player's Guide. Unfortunately I can't find it right now, perhaps someone else that has it can check? If I'm right, this is further proof that the Northern Kremisphere is in fact a continent.