Exploring high latitude geomagnetic field behaviour in the northern hemisphere over the past four millennia

English Abstract:

Geomagnetic field observations at the Earth’s surface provide a powerful probe of the dynamics of the top of the core, and ultimately of the whole geodynamo. Field reconstructions for the present day are characterised by the two pairs of intense high latitude flux patches at the core mantle boundary, which are approximately symmetric about the equator. These so-called flux lobes have remained relatively stationary over the past four centuries, which has been interpreted in terms of mantle control on the geodynamo. The recently published pfm9k family of models, based on palaeomagnetic data, suggests a more dynamic field behaviour on millennial times scales, predicting dominant westward drift of flux lobes over the past 4000 years. These models were intentionally smoothed in time (approximately averaged over 400 years) to address the large chronological uncertainties and also often low temporal resolution of the sedimentary palaeomagnetic dataset. Here we will investigate ways to increase the temporal resolution of the models with an emphasis on using selected high-resolution sediment records from mid to high latitudes in the northern hemisphere. The results are used to inform the robustness of the pfm9k model predictions and provide new insights into the millennial scale behaviour of the geomagnetic field.