Q. For the purpose of Halacha, (following the above shailes on dateline, see questions above) what does someone do when he finds himself at one of the Earth Poles in regards to Shabbos and mitzvos observance? Do we follow the Geographic or the Magnetic Pole?

A. One of the main reasons why a dateline is essential, as explained by the Poskim, is to avoid the case of two individuals that began traveling around the globe in opposite directions and then convened again, having to observe Shabbos together on different days. However, the above cannot be avoided at the poles, where two travelers that originated from different date zones, may indeed be keeping Shabbos together in different days. The same may apply to one traveling in a boat and meeting a fellow traveler on another vessel coming towards him at exactly one of the datelines. However, Horav Shlomo Miller Shlit’a explained, that due to the unusual and uncommon probability of the happening, we do not take it into consideration. He added, that the same may apply to the poles.
The Rov Shlit’a also clarified that we follow usually the geographic poles.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a