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Reality of a UV window during the geomagnetic excursion event of Mono Lake-Laschamps and possible link to the disappearance of the Neanderthals

Project description

Earth’s magnetic field and the disappearance of the Neanderthals

Earth’s magnetic field has decreased about 20 % over the past 150 years. As Earth is constantly subjected to cosmic radiation, the intensity depends on the strength of the magnetic field. Over geological timescales, there have been periods of collapse of the magnetic dipole moment, and therefore of the magnetic field, which can be associated with changes in the polarity of the dipole or with simple geomagnetic excursions (GEs). UV radiation can penetrate deeper into the atmosphere during these periods. The EU-funded REVA project will study this UV window during the Mono Lake-Laschamps GE events. This is important considering its globality and the possible implications for human evolution (contemporaneous with the disappearance of the Neanderthals).

Objective

"The Earth is constantly subjected to cosmic radiation, the intensity of which, at the level of the upper atmosphere and the Earth's surface, depends on the strength of the magnetic field (MF) surrounding our planet. Over geological timescales, there have been periods of collapse of the magnetic dipole moment, and therefore of the MF, which can be associated with changes in the polarity of the dipole or with simple geomagnetic excursions (GE). GE events (typically lasting ~1ka to ~10ka) generate an increase in cosmic bombardment in the upper atmosphere and, ultimately, through chemical effects the destruction/thinning of the ozone layer. During these periods UV radiation can penetrate deeper into the atmosphere, while it is otherwise absorbed by the ozone layer. Yet, the reality of such a UV ""window” has never been attested by natural observations, which if present during GE events in the future would have significant environmental and above all human consequences. This is plausibly foreseen in a short term as the intensity of Earth’s MF has decreased (~20%) over the past 150 years and with an accelerated rate in the last decades (> ~10 times the normal). The aim of this project is, therefore, to test the reality of a UV window during the Mono Lake-Laschamps (~ -40 ka) GE event, which by its magnitude, its globality and the possible implications for human evolution (being contemporaneous with the disappearance of the Neanderthals), is an example of a remarkable case study. Here, by measuring stable isotopic composition of sulfur (S) at high resolution (<200 years) in ice cores taken in Antarctica, we will leverage peculiar aspects of atmospheric chemistry of the S-33 isotope. In the absence of ozone, the interaction between SO2 and UV radiation, through photochemical processes, generates mass-independent (Δ) signatures. We propose to trace a possible UV ""window"" by analyzing the evolution of the observed ΔS-33 anomaly and model the extent of depletion of ozone layer."

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Coordinator

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
Net EU contribution
€ 196 707,84
Address
Rue michel ange 3
75794 Paris
France

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Region
Ile-de-France Ile-de-France Paris
Activity type
Research Organisations
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Other funding
€ 0,00