CONICET | Buscador de Institutos y Recursos Humanos

During the last decades, the interrelationships between geomagnetic field (GF) variations, paleoclimates, and Milankovitch cycles were the subject of numerous research studies. The GF could have acted as a paleoclimate forcing, interacting with the cyclicity of the orbital parameters. In this contribution, we evaluated the relationship between the GF variations, ocean paleotemperatures, orbital parameters, and an insolation forcing, covering the last 500 kyr using wavelets, cross wavelets, and multiple cross wavelets. The new multiple cross wavelet algorithms (Velasco Herrera et al. 2017) allowed the analysis of more than two-time series and know their relative phase relationships. The results of the wavelet analysis showed the eccentricity as the main forcing for the GF relative paleointensity (RPI) and the paleotemperatures time series. These results could suggest that the GF variations influenced the climate, or the same orbital forcing could have influenced both GF and climate. The results of the multiple cross wavelet analysis between RPI and the orbital parameters showed the precession as the main periodicity (~23 kyr) with higher spectral power when the eccentricity is maxima. Thus, we noted that the eccentricity modulated the GF behavior, and the precession could have been related to some short-term GF variations, being both precursors of GF changes. During Marine Isotope Stage (MIS) 5, the GF could have played an important role as an indirect climate forcing. During this period, two GF reversals (Blake at ~120 kyr, and post-Blake at ~100 kyr) could have been associated with relative climate cooling after the Last Interglacial climax (MIS 5e). The GF reversals could have been precursor forcings creating positive synergy with the insolation changes. The Blake event promoted the end of MIS 5e and the beginning of the relatively colder MIS 5d, and the post-Blake event occurred at the end of MIS 5c and could have contributed to the beginning of the relatively colder MIS 5b. Thus, during these GF reversals, the conjunction of the absence or weakening of magnetic shielding and downward insolation, both forced by the orbital cyclicity, could have relatively cooled the planet.