Was Nansen following the magnetic field around the Birkeland current?
On page 201 of Farthest North, Fridtjof Nansen describes how his progress is skewed towards the west,
"This morning I made out our latitude and longitude. The former was (Sunday, May 5th) 84° 31′ N., and the latter 66° 15′ E. We were not so far south as I expected, but considerably farther west. It is the drift which has put us back and westward. I shall, therefore, for the future, steer a more southerly course than before, about due south (true), as we are still drifting westward, and, above everything, I am afraid of getting too far in that direction. It is to be hoped that we shall soon have land in sight, and we shall then know where to steer. We undoubtedly ought to be there now. "
As he had no other explanation, he assumes the ice as a whole that he is on must be drifting. He describes coming to that conclusion on page 164 of the same book,
"It became more and more of a riddle to me that we did not make greater progress northward. I kept on calculating and adding up our marches as we went along, but always with the same result; that is to say, provided only the ice were still, we must be far above the eighty-sixth parallel. It was becoming only too clear to me, however, that the ice was moving southward, and that in its capricious drift, at the mercy of wind and current, we had our worst enemy to combat. "
Was Nansen following the magnetic field around the Birkeland current?
The Birkeland current entering the Earth through the north pole, would create a magnetic field around itself, which is oriented clockwise with north pointing towards the east in the Earth magnetic field. An alternative hypothesis to why Fridtjof Nansen seemed to move westward could be that his compass was pointing towards the magnetic north of the magnetic field around the Birkeland current.
The magnitude of the magnetic field around a wire is based on the amount of charge, how much current is running through the wire, i.e. how much current is flowing through the Birkeland current, and also the radius. Assuming the Earth is "charged" by the sun, there would be a strong magnetic field around the current coming into the north pole, that would affect compasses and fool polar explorers like Fridtjon Nansen who assume their compass is pointing towards the Earth's magnetic north.