Proponents of the Bi-Polar Model argue that there are actually two poles and that the magnetic field lines resemble something like that a bar magnet, the compass pointing to either pole to take the navigator around it. The Antarctic circumnavigation is relatively unquestioned under this model.
Circumnavigation involves traveling Eastwards or Westwards in relation to the magnetic field lines. On a Bi-Polar model the magnetic field lines would spread out from the North and South poles like the magnetic field lines on a bar magnet.
The needle of a compass would align with those magnetic field lines in the navigator's local area. Since East and West are at right angles to the field lines, moving East or West in relation to those field lines would take one in a circle around the North or South poles. This also implies that if one were to follow the magnetic field lines North or South that they would eventually get to the North South poles.
It should be noted that the magnetic field lines on a magnet always wrap around and connect to the opposite pole and do not travel forever into space.