Lunar eclipses as a proxy for investigating the chronology and climate impact of volcanism during the Little Ice Age
Résumé
Explosive volcanism is one of the main drivers of natural climate variability. The massive injection of sulfate aerosols into the upper atmosphere leadsto the reflection ofsolar radiation, causing a temporary cooling of the Earth’s surface and disrupting the entire climate system. However, the chronology, the estimates of the altitude (tropospheric vs. stratospheric) and the burden of volcanic aerosols of these events are still subject to uncertainties, despite progress in the study and dating of ice cores. Descriptions of lunar eclipse observations mentioned in historical texts can provide valuable insights for estimating the chronology and impact of volcanism over the past millennium. The visibility of lunar eclipses is influenced by the amount of volcanic aerosols present in the upper atmosphere. After largemagnitude eruptions, eclipses tend to appear darker due to the reduced refraction of solar radiation within Earth’s shadow cone caused by the increased concentration of aerosols. We propose here to refine existing data on explosive volcanism and its impact on climate during the period 1600-1800 CE based on texts describing 94 total lunar eclipses. Drawing on over 900 documents, we were able to rate the color of the moon of 60 total eclipses using the Danjon scale. These data allow us to construct a chronology of stratospheric turbidity, expressed as sulfate aerosol optical depth (SAOD) values. This new SAOD chronology derived from historical records has been compared with bipolar ice core data, aerosol models (AOD; aerosol optical depth), and climate data based on tree rings. First results show that our SAOD data are consistent with the estimated AOD data from Sigl et al. (2015) and Toohey and Sigl (2017). Moreover, when comparing the Nvolc2 Northern Hemisphere tree-ring based climate reconstruction (Guillet et al., 2020), which is highly sensitive to volcanic forcing derived from volcanic sulfate deposition in ice cores (r = -0.61, p < 0.001), we observe that of the 10 coldest years within the 40 years for which we have eclipse color data, 7 correspond to the darkest observed eclipses (SAOD > 0.02). These findings suggest that lunar eclipses could be a useful proxy for more accurately reconstructing the chronology and impact of volcanism during the Little Ice Age, as has already been done for the period 1100-1300 CE (Guillet et al., 2023). However, certain events within our chronology that are inconsistent with AOD and climate data will be discussed, as well as the limitations of this new approach.
Domaines
Sciences de l'environnementOrigine | Fichiers produits par l'(les) auteur(s) |
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