Dasari, S.; Paris, G.; Charreau, J.; Savarino, J.
PNAS Nexus, 2022, 1, 1-9
Voir en ligne : https://doi.org/10.1093/pnasnexus/pgac170
Abstract :
Changes in the cosmic-ray background of the Earth can impact the ozone layer. High-energy cosmic events [e.g. supernova (SN)] or rapid changes in the Earth’s magnetic field [e.g. geomagnetic Excursion (GE)] can lead to a cascade of cosmic rays. Ensuing chemical reactions can then cause thinning/destruction of the ozone layer—leading to enhanced penetration of harmful ultraviolet (UV) radiation toward the Earth’s surface. However, observational evidence for such UV “windows” is still lacking. Here,we conduct a pilot study and investigate this notion during two well-known events: the multiple SN event (≈10 kBP) and the Laschamp GE event (≈41 kBP).We hypothesize that ice-core-Δ33S records—originally used as volcanic fingerprints—can reveal UV-induced background-troposphericphotochemical imprints during such events. Indeed, we find nonvolcanic S-isotopic anomalies (Δ33S ≠ 0‰) in background Antarctic ice-core sulfate during GE/SN periods, thereby confirming our hypothesis. This suggests that ice-core-Δ33S records can serve as a proxy for past ozone-layer-depletion events