Assessing Atmospheric Impacts of the Hunga Tonga-Hunga Ha'apai Volcanic Eruption and Using It as a Natural Experiment to Evaluate an Earth System Model

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Volcanic eruptions can affect weather and climate through several different mechanisms. For example, highly explosive eruptions, like that of Mt. Pinatubo in 1991, often produce sulfur-containing droplets and particles high in Earth’s atmosphere. There, these aerosols scatter sunlight back to space and can cool global climate for more than a year. On January 15, 2022, the Hunga Tonga–Hunga Ha'apai volcano erupted explosively in the South Pacific. Satellite observations showed that the eruption introduced surprisingly little sulfur to the atmosphere but injected an enormous amount of water vapor into the stratosphere, about 10-20 miles above Earth’s surface. Water vapor is a greenhouse gas and is particularly effective at warming climate when it is in the stratosphere, where only trace amounts of water generally exist. The eruption increased the total global stratospheric water vapor content by roughly 10%, representing the largest single-source injection of stratospheric water vapor ever observed from space, and furthermore this excess water could persist for 5-10 years. The Tonga eruption therefore represents an unprecedented natural experiment on Earth’s atmosphere. This investigation will use observations and modeling to assess the atmospheric impacts of the eruption, including its effects on Earth’s energy budget via alterations to the amount of sunlight and infrared energy absorbed and emitted by the planet. The investigators will assess how the eruption affected stratospheric temperatures, circulation patterns throughout the atmosphere, and the annual ozone hole formation over Antarctica, which may be perturbed through chemical and physical mechanisms related to the eruption. More broadly, this project will evaluate how well an Earth System Model captures the observed perturbations to Earth’s atmosphere in the years following the eruption and identify improvements to models that remedy any deficiencies that are found. In a broader sense, this project will contribute to an improved understanding of the atmospheric and climate impacts and risks to global society posed by large volcanic eruptions, particularly those that erupt beneath the ocean surface like the 2022 Tonga event. Records of past volcanic activity recorded in ice cores from Greenland and Antarctica indicate that eruptions ten times more powerful than the 2022 Tonga event occur roughly once every 625 years, with potentially severe impacts on civilization. The scientists involved in this project will conduct simulations of such events to explore their potential impacts. They will also adapt an Earth System Model so that it can be used more readily by the scientific community to comprehensively study climate impacts from volcanic eruptions, for example by improving the ability of the model to track and isolate the influences of volcanic water vapor, sulfur, and ash. Finally, the investigators will train and mentor a Ph.D. student for this project and expand the material on volcano-climate interactions presented in the graduate- and undergraduate-level courses. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.