Full vector spherical harmonic analysis of the Holocene geomagnetic field

• Main Author: Richardson, Marcia
• Format: Dataset
• Language: English
• Published: University of Southern California Digital Library (USC.DL) 2015
• Subjects: Geological Sciences; paleomagnetic field; Arctic; North Pole
• Online Access: https://dx.doi.org/10.25549/usctheses-c3-385115; https://digitallibrary.usc.edu/asset-management/2A3BF1LJJAAY

High‐quality time‐series paleomagnetic measurements have been used to derive spherical harmonic models of Earth's magnetic field for the past 2,000 years. A newly‐developed data compilation, PSVMOD2.0 consists of time‐series directional and intensity records that significantly improve the data quality and global distribution used to develop previous spherical harmonic models. PSVMOD2.0 consists of 185 paleomagnetic time series records from 85 global sites, including 30 full‐vector records (inclination, declination and intensity). It includes data from additional sites in the Southern Hemisphere and Arctic and includes globally distributed sediment relative paleointensity records, significantly improving global coverage over previous models. PSVMOD2.0 records have been assessed in a series of 7 regional intercomparison studies, four in the Northern Hemisphere and 3 in the southern hemisphere. Comparisons on a regional basis have improved the quality and chronology of the data and allowed investigation of spatial coherence and the scale length associated with paleomagnetic secular variation (PSV) features. We have developed a modeling methodology based on nonlinear inversion of the PSVMOD2.0 directional and intensity records. Models of the geomagnetic field in 100‐year snapshots have been derived for the past 2,000 with the ultimate goal of developing models spanning the past 8,000 years. We validate the models and the methodology by comparing with the GUFM1 historical models during the 400‐year period of overlap. We find that the spatial distribution of sites and quality of data are sufficient to derive models that agree with GUFM1 in the large‐scale characteristics of the field. We use the the models derived in this study to downward continue the field to the core‐mantle boundary and examine characteristics of the large‐scale structure of the magnetic field at the source region. The derived models are temporally consistent from one epoch to the next and exhibit many of the expected characteristics of the field over time (high‐latitude flux lobes, South Atlantic reverse flux patch, north pole reverse or null flux region).