학술논문
Sulfur-isotope anomalies recorded in Antarctic ice cores as a potential proxy for tracing past ozone layer depletion events
Research Report
Research Report
Document Type
Academic Journal
Source
PNAS Nexus. September 2022, Vol. 1 Issue 4
Subject
Language
English
ISSN
2752-6542
Abstract
Significance Statement: The ozone layer in the upper troposphere-lower stratosphere (UTLS) region absorbs ultraviolet (UV) radiation, thereby limiting the penetration of harmful UV rays into the Earth's atmosphere. However, in [...]
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 ([approximately equal to]10kBP) and the Laschamp GE event ([approximately equal to] 41 kBP). We hypothesize that ice-core-[DELTA][sup.33]S records--originally used as volcanic fingerprints--can reveal UV-induced background-troposphericphotochemical imprints during such events. Indeed, we find nonvolcanic S-isotopic anomalies ([DELTA][sup.33]S = 0[per thousand]) in background Antarctic ice-core sulfate during GE/SN periods, thereby confirming our hypothesis. This suggests that ice-core-[DELTA][sup.33]S records can serve as a proxy for past ozone-layer-depletion events. Keywords: cosmic-ray background, UV radiation, sulfur mass-independent fractionation (S-MIF), [DELTA][sup.33]S
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 ([approximately equal to]10kBP) and the Laschamp GE event ([approximately equal to] 41 kBP). We hypothesize that ice-core-[DELTA][sup.33]S records--originally used as volcanic fingerprints--can reveal UV-induced background-troposphericphotochemical imprints during such events. Indeed, we find nonvolcanic S-isotopic anomalies ([DELTA][sup.33]S = 0[per thousand]) in background Antarctic ice-core sulfate during GE/SN periods, thereby confirming our hypothesis. This suggests that ice-core-[DELTA][sup.33]S records can serve as a proxy for past ozone-layer-depletion events. Keywords: cosmic-ray background, UV radiation, sulfur mass-independent fractionation (S-MIF), [DELTA][sup.33]S