While researching this answer, I learned that there about 5 times per year between late July and September, there are passenger boats from Yakutsk all the way north to Tiksi at 71°39' north. For comparison, the Norwegian North Cape is at 71°10' north and Prudhoe Bay, Alaska is quite far south at 70°20'N, so this passenger boat goes further north than one can drive in either Europe or North America. In fact, to get to Tiksi the boat has to pass along the mouth of the Lena River at 72°25'N before calling at Быковский / Bykovskiye (72°00'N) just north of Tiksi.
Lenaturflot route Yakutsk–Tiksi. Source: Lenaturflot.
What is the furthest north one can get, using only public (winter) roads or regular land-based public transportation? By regular public transportation, I mean public transportation that primarily exists to service communities along the way, as opposed to cruises that exist primarily/exclusively for entertainment purposes. Is Tiksi the northernmost?
Assume a starting point in any capital city in mainland Europe or mainland North America (connected by ocean liner, so either continent counts); any point that can be reached without flying from at least one such capital city counts (I think those are all inter-connected by public transport anyway).