P2C2: Signatures of the Toba Super-eruption in Borneo Stalagmites

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This award supports the collection of well-dated stalagmites from the Gunung Mulu National Park in northern Borneo to generate paired reconstructions of high resolution atmospheric volcanic loading, as determined by micro-scale analyses of volcanic ash and volatiles, and stalagmite delta oxygen-18 isotopes (delta-18O), as a proxy for hydroclimate. Large volcanic eruptions have a significant cooling effect on climate through the radiative effects of sulfate aerosols and, as such, represent key targets for a quantitative data-model inter-comparison. As the largest eruption of the last 2 million years, the Toba super-caldera, located on the island of Sumatra, Indonesia, spread a thick layer of ash from East Africa to the South China Sea when it erupted roughly 74,000 years ago. The eruption's climatic attribution is complicated by a millennial-scale abrupt climate change event that is closely associated in time with the eruption. Numerical climate model simulations confirm that an eruption of Toba's size would have had significant impacts on global climate despite significant uncertainties regarding the size and duration its radiative effects. With these datasets, the researchers aim to determine the relative timing of Toba ash loading with respect to stalagmite delta-18O anomalies indicative of regional hydroclimate impacts. They will compare their hydro-climate reconstructions with output from the water isotope-equipped NASA/GISS ModelE2-R using an existing suite of simulations forced with large volcanic eruptions.Stalagmites have provided exceptionally well-dated, high-resolution reconstructions of climate in many areas of the world, yet only a handful of studies have investigated their use as archives of volcanic forcing histories. The Borneo stalagmites represent an opportunity to pursue such absolutely-dated reconstructions and to directly compare them to reconstructions of hydro-climate across the time horizon of an exceptionally large eruption. This award carries with it strong ongoing public outreach efforts in climate science such as organizing a public symposium on "How Climate Works" involving local high school science classes and offering summer research internships to those that attend as well as spearheading an initiative to establish a permanent archive for the Gunung Mulu stalagmites to ensure access to the valuable samples for other scientists.