The wandering of Earth’s north magnetic pole, the location where the magnetic field points vertically downwards, has long been a topic of scientific fascination. Since the first in situ measurements in 1831 of its location in the Canadian arctic, the pole has drifted inexorably towards Siberia, accelerating between 1990 and 2005 from its historic speed of 0–15 km yr⁻¹ to its present speed of 50–60 km yr⁻¹. In late October 2017 the north magnetic pole crossed the international date line, passing within 390 km of the geographic pole, and is now moving southwards. Here we show that over the last two decades the position of the north magnetic pole has been largely determined by two large-scale lobes of negative magnetic flux on the core–mantle boundary under Canada and Siberia. Localized modelling shows that elongation of the Canadian lobe, probably caused by an alteration in the pattern of core flow between 1970 and 1999, substantially weakened its signature on Earth’s surface, causing the pole to accelerate towards Siberia. A range of simple models that capture this process indicate that over the next decade the north magnetic pole will continue on its current trajectory, travelling a further 390–660 km towards Siberia.

长期以来，人们一直迷恋着地球的北磁极，即磁场垂直指向下方的位置。自从1831年首次在加拿大北极地区进行实地测量以来，该极点就无情地向西伯利亚漂移，在1990年至2005年期间从其历史速度0-15 km yr ^-1加速到目前的50-60 km yr ^-1。2017年10月下旬，北磁极越过国际日期变更线，经过地理极的390公里以内，目前正在向南移动。在这里，我们表明，在过去的二十年中，北磁极的位置在很大程度上取决于加拿大和西伯利亚下的岩心—地幔边界上的两个大的负磁通量波瓣。局部模型表明，加拿大叶的伸长可能是由于1970年至1999年间岩心流动模式的改变而引起的，从而大大削弱了其在地球表面的标志性作用，使极加速了向西伯利亚的移动。一系列捕捉这一过程的简单模型表明，在未来十年中，北磁极将继续其当前轨迹，向西伯利亚再行进390-660公里。