PERIODICITIES OF THE GEOMAGNETIC FIELD DURING THE HOLOCENE. POSSIBLE FORCINGS

CAPPELLOTTO LUIGGINA; CAPPELLOTTO L.; ACHAGA R.; ORGEIRA, M.J.; C. S. G. GOGORZA; VELASCO HERRERA VÍCTOR MANUEL

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Congreso; 6th PAGES Open Science Meeting; 2022

PAGES

Several studies in different records show that paleoclimate variations during the lateCenozoic would have been moderated mainly by changes in insolation through orbitalcyclicality. In the last decades, the analysis of the mechanisms and possible periodicitiesof the geomagnetic field (GF) variations has aroused great interest in climate forcingstudies. Numerous authors have made different proposals on the relationship between GFvariations and orbital cycles. However, the link between orbital frequencies and GF-related processes is still under debate, gaining significance mainly because of thesynergistic effect with other climate forcings. Moreover, studying this connection in theHolocene acquires significance due to the remarkable weakening trend of the GFintensity, at least during the last 500 years.To estimate that relationship, we performed a wavelet analysis (Velasco Herrera et al.2017) on time series of GF paleosecular variations (Declination, Inclination, and relativepaleointensity, RPI) from the best South American lacustrine records (Patagonia,Argentina). The records involved sediment cores from three Patagonian lakes: El Trébol(41°04′S, 71°29′W), Escondido (41°S, 71°30W), and Potrok Aike (51°58′S, 70°23′W),and they cover the entire Holocene.We analyzed the coherence of the oscillations registered in the magnetic records, usingwavelet, cross wavelet, and a new methodology based on multiple cross wavelets todetermine the possible existence of some typical common patterns in the time seriesinvolved and explain the possible origin of each periodicity found. The multiple crosswavelet analysis performed on the magnetic data from the three lakes showed variationswith periodicities around 1500 and 3000 years. We also performed a wavelet analysis ona benthic isotopic record (δ18O) since it is a time series representing the paleotemperaturesof the South Atlantic Ocean. Periodicities close to 1500 and 3000 years were alsorecorded in this paleoclimate proxy. The results obtained would indicate similarrhythmicity and certainty in the variations on the climate and GF.Therefore, we speculated that the GF could act as one of the climatic forcings, or that GFand climate oscillate together due to the influence of the same forcing external to theplanet. As it is a complex system and according to our results, we suggest that externalforcings could promote the variations of the GF and climate during the Holocene.