Atmosphere injection of sea salts during the 15 January 2022 submarine eruption of Hunga volcano, Tonga

The 15 January 2022 submarine eruption at Hunga volcano was the most explosive volcanic eruption in 140 years. It involved exceptional magma and seawater interaction throughout the entire submarine caldera collapse. The submarine volcanic jet breached the sea surface and formed a subaerial eruptive plume that transported volcanic ash, gas, sea salts and seawater up to ~ 57 km, reaching into the mesosphere. We document high concentrations of sea salts in volcanic ash collected shortly after deposition. We discuss the potential climatic consequences of large-scale injection of salts into the upper atmosphere during submarine eruptions. Sodium chloride in these volcanic plumes can reach extreme concentrations, and dehalogenation of chlorides and bromides poses the risk of long-term atmospheric and weather impact. We also discuss high concentrations of Ca-sulfates, originating from both seawater-ash interaction and gas scavenging of SO2 within ash aggregates. The discrepancy between the SO2 measured by satellites and values expected from degassing may be explained by a combination of such SO2 uptake and additional SO2 release to the sea via passive degassing prior to the eruption or with ejecta in submarine gravity currents. The balance between salt loading into the atmosphere versus deposition in ash aggregates is a key factor in understanding the atmospheric and climatic consequences of submarine eruptions.