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

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 (approximate to 10kBP) and the Laschamp GE event (approximate to 41kBP). We hypothesize that ice-core-Delta S-33 records-originally used as volcanic fingerprints-can reveal UV-induced background-tropospheric-photochemical imprints during such events. Indeed, we find nonvolcanic S-isotopic anomalies (Delta S-33 not equal 0 parts per thousand) in background Antarctic ice-core sulfate during GE/SN periods, thereby confirming our hypothesis. This suggests that ice-core-Delta S-33 records can serve as a proxy for past ozone-layer-depletion events.

Automated summary

Changes in the cosmic-ray background can affect the Earth's ozone layer, leading to increased penetration of harmful UV radiation. By studying ice-core ΔS-33 records, we have confirmed the link between UV-induced atmospheric photochemical imprints and past ozone-layer depletion events.