Global Geomagnetic Field Reconstructions from Centuries to Excursions

Three projects within the SPP Planetary Magnetism dealt with reconstructing past geomagnetic field morphology and variations based on paleo- and archeomagnetic data in order to better understand global field characteristics and underlying processes. Their aims were as follows: (1) Obtaining a detailed reconstruction of the field for the past ten centuries, particularly focussing on the reliable reconstruction of the dipole moment prior to the invention of direct absolute intensity observations in 1833. The combination of direct historical observations and young archeomagnetic results with very different uncertainty characteristics and global distributions is a challenge. (2) Improving Holocene geomagnetic field models and (3) developing global reconstructions of the Laschamp ( ∼ 41 ka) and Mono Lake ( ∼ 33 ka) magnetic field excursions. High-quality data and a good understanding of data and age uncertainties are the prerequisite for long-term geomagnetic field models. Upgrading the GEOMAGIA50 database for archeomagnetic and volcanic data spanning the past 50 ka years and adding a new part for sediments were important achievements in this regard. The database now offers possibilities to update age-depth models of individual records or reassess multiple core correlations. Additionally, new sediment records were obtained from African and American low latitudes and from lava flows on Fogo, Cape Verde Islands, in order to better constrain the region of the present-day South Atlantic Anomaly. The projects are presented in the context of reviewing recent international progress towards better understanding of the geomagnetic field evolution on centennial to millennial timescales.