Sulfur-isotope anomalies recorded in Antarctic ice cores as a potential proxy for tracing past ozone layer depletion events

• Published in: PNAS Nexus
• Main Authors: Dasari, Sanjeev, Paris, Guillaume, Charreau, Julien, Savarino, Joel
• Other Authors: McSween, Harry, Centre National de la Recherche Scientifique
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2022
• Subjects: Antarctic; Antarc*; ice core
• Online Access: http://dx.doi.org/10.1093/pnasnexus/pgac170; https://academic.oup.com/pnasnexus/advance-article-pdf/doi/10.1093/pnasnexus/pgac170/45617105/pgac170.pdf; https://academic.oup.com/pnasnexus/article-pdf/1/4/pgac170/48849682/pgac170.pdf

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-tropospheric-photochemical 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.