Correspondence to lw602@cam.ac.uk
This GitHub Repository contains all of the Jupyter Notebooks used for data analysis and visualisation in this project. Please use the Figure Reference Table.docx to refer to the corresponding notebook used for each figure in the report.
The folder /Data contains all proxy data files used in this project. Data from the UKESM1 is available on request.
See the Abstract below for a summary of this project and its key findings:
The Samalas eruption, suggested to have occurred between 1256-1258 AD, was one of the largest eruptions of the Holocene epoch. With a Volcanic Explosivity Index of 7, the eruption column is estimated to have reached altitudes of 43 km and injected an estimated 119 Tg of SO2 into the stratosphere. Proxy data suggest a northern hemisphere summer cooling of -0.7 to -1.2°C for 1258, although previous attempts to simulate the climatic impact of the eruption have tended to overestimate the eruption’s surface temperature response. Proxy data suggest significant regional heterogeneity in temperature and precipitation anomalies, with the eruption’s climatic impact being invoked to account for a range of 13th century social and economic phenomena. Uncertainties remain over the timing of the eruption, with dates being suggested from between April 1256 to January 1258. Using the UK Earth System (UKESM1) climate model, simulations were run for the Samalas eruption starting in either January 1258 or July 1257 with a range initial Quasi-Biennial Oscillation and El Niño Southern Oscillation conditions. Combined with proxy data and historical records a model multi-proxy framework has been utilised to place constraints on best-fit eruption source parameters and initial conditions. Overall, this approach favours a July 1257 eruption date, although due to proxy uncertainties a January 1258 date cannot be completely ruled out. El Niño eruption initial conditions achieve the most complete agreement with spatially reconstructed surface temperature anomalies, however, no robust constraint can be placed on the phase of the Quasi-Biennial Oscillation at the point of the eruption. The role of eruption source parameters and initial conditions in modulating the eruption’s climatic impact has also been investigated. A strong link between aerosol distribution, hemispheric temperature contrasts, resulting meridional shifts in the Inter-Tropical Convergence Zone and changing wind dynamics across the equatorial Pacific, has implications for the proposed ITCZ-teleconnection mechanism in explaining the occurrence of El Niño-like anomalies in the year following a volcanic eruption.