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

火山爆发可以通过几种不同的机制影响天气和气候。例如，高度爆炸性的喷发，如Mt。1991年皮纳图博火山爆发时，经常在地球大气层高处产生含硫的液滴和颗粒。在那里，这些气溶胶将阳光散射回太空，可以使全球气候冷却一年多。2022年1月15日，南太平洋的Hunga Tonga-Hunga Ha'apai火山爆发。卫星观测显示，火山爆发向大气中引入的硫少得令人惊讶，但向地球表面上方约10-20英里的平流层注入了大量的水蒸气。水蒸气是一种温室气体，当它在平流层时，在气候变暖方面特别有效，因为平流层通常只有微量的水存在。这次喷发使全球平流层水蒸气含量增加了约10%，这是有史以来从太空观测到的最大的平流层水蒸气单一来源注入，而且这些多余的水可能持续5-10年。因此，汤加火山爆发是对地球大气层的一次前所未有的自然实验。这项调查将利用观测和建模来评估火山爆发对大气的影响，包括通过改变地球吸收和发射的阳光和红外线能量对地球能量预算的影响。研究人员将评估火山喷发如何影响平流层温度、整个大气层的环流模式以及南极洲上空每年形成的臭氧洞，这些臭氧洞可能通过与火山喷发有关的化学和物理机制而受到干扰。更广泛地说，该项目将评估地球系统模型在多大程度上捕捉到了火山爆发后几年中观测到的地球大气扰动，并确定对模型的改进，以弥补发现的任何缺陷。特别是那些在海洋表面下爆发的火山，比如2022年的汤加火山事件。格陵兰岛和南极洲冰芯中记录的过去火山活动记录表明，大约每625年发生一次比2022年汤加事件强大十倍的火山爆发，可能对文明造成严重影响。参与该项目的科学家将对此类事件进行模拟，以探索其潜在影响。他们还将调整地球系统模型，以便科学界更容易使用它来全面研究火山爆发的气候影响，例如通过提高模型跟踪和隔离火山水蒸气，硫和灰烬影响的能力。 最后，研究人员将培训和指导一位博士。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.