Tonga volcanic eruption triggered anomalous Arctic warming in early 2022

On 15 January 2022, the submarine volcano on Hunga Tonga-Hunga Ha'apai Island erupted and injected a small amount of SO2 but an unprecedent amount of water vapor into the stratosphere. The impact of Tonga eruption on climate was dynamically simulated using a fully coupled climate prediction system FIO-CPS v2.0 by considering both SO2 and water vapor injections into the stratosphere, which is the first attempt to incorporate the volcanic water vapor injection in a climate prediction system to evaluate its effect on surface climate response. Model results indicated that the surface air temperature (SAT) over the Arctic region was significantly warmer in early 2022 as a response to the co-injection of SO2 and water vapor from Tonga eruption, although its effect on global mean SAT was found to be insignificant. In February 2022, the average warming anomaly in the Arctic area reached up to 1.1 degrees C, with zonal mean warming of 2.0 degrees C near the North Pole. The Tonga eruptions induced anomalous heat transport which primarily contributed to the Arctic warming in February. However, it had a cooling effect on the Arctic area in January and March. In addition to heat transport, the eruption also triggered anomalous northward transport of water vapor. This led to an increase in the water vapor content, which further enhanced the downward longwave radiation and cloud-radiative feedback over the Arctic region, ultimately contributing to the Arctic SAT warming in early 2022. In the simulation only SO2 injection was considered without water vapor injection, the pattern of SAT response showed warming over the Eurasian continent and cooling in the north over Arctic Ocean, which is opposite to that in the simulation with co-injection of SO2 and water vapor. This indicated that volcanic water vapor injection of Tonga eruption played a dominant role in the Arctic warming. Consequently, submarine volcano should receive more attention due to its potential climate effects, especially when it involves significant water vapor releases.