Fluctuation of the Earth's magnetic field elements in Mexico revealed by archive documents since 1587

Historical documents, archives and old photographic collections allowed to analyze 877 direct geomagnetic measurement data obtained by sailors (including pirates), United States Coast and Geodetic Survey and National Astronomical Observatory since 1587. The updated catalogue includes 844 values of magnetic declination, 495 of inclination, 467 of the horizontal intensity component (H) and 455 of the vertical intensity component (Z). All data were relocated to Mexico City through the pole conversion method in order to build a reference secular variation curve for Mexico and surrounding area using bootstrap method to mitigate the effect of outliers and estimate the probability of density functions. The directional variation patterns obtained in this investigation were compared to the curves retrieved from Sha.Dif.14k, GUFM1and IGRF-12 models while VADM fluctuations were confronted to similar quality determinations from other localities worldwide as well as archaeomagnetic curves from Mesoamerica. •Historical documents allowed to analyze 877 direct geomagnetic measurement data since 1587.•A reference secular variation curve was constructed using bootstrap method.•A potential geomagnetic jerk was detected at about 1850 already reported for Balkan region.