Powerful volcanic eruptions inject large amounts of sulphur dioxide into the stratosphere that converts to sulphate aerosol, thereby altering its radiative properties and leading to short-term (1–3 years), global-scale cooling at the surface (Robock, 2000). Analysis of such surface cooling can be studied with proxies such as tree rings or historical sources. However, previous analyses have so far been dedicated exclusively to the Northern Hemisphere (NH), for which more archival data and a better coverage of tree-ring reconstructions. Comparatively, little attention has been paid to the Southern Hemisphere (SH), and more specifically to South America where the impacts of volcanic eruptions have not been studied neither on temperature nor on precipitation.
Therefore, the goal of the ARAUCARIAproject proposal is to reveal the impact of the 12 largest eruptions of the last 500 years in Brazil and to retrospectively assess and quantify their climatic and environmental impacts. For this purpose, a new multi-centennial tree-ring reconstruction will be developed from Araucaria angustifolia,an indigenous climate-sensitive conifer tree from Southern Brazil. Three parameters will be studied with the newly developed chronology: (i) tree-ring width parameter will be used to perform temperature reconstruction and ENSO reconstruction for the past half-millennium; (ii) isotopes analyses (13C/12C and18O/16O) in cellulose of tree-rings will be used to reconstruct past hydroclimatic variability following these eruptions.
The ARAUCARIA project is dedicated to a topic which has remained largely unstudied in South America, but for which results can be expected with reasonable efforts. The fact that the Brazilian team has past experience with tree-ring analysis and state-of-the-art tools to study the dispersion of volcanic material in the stratosphere will be the first central pillar for a successful completion of this project. The Swiss (and French) teams will bring in their expertise in the reconstruction of volcanic cooling signals in tree ring records as well as their background on isotope analyses. Together, the teams will be highly complementary and thus bring all ingredients needed for a successful project.
Prof. Markus Stoffel
Prof. Heitor Evangelista da Silva