Abstract

There is widespread consensus that volcanic sulphate aerosols in the stratosphere can restrict solar energy reaching the earth's surface for years, so reducing surface temperatures, modifying global circulation patterns, and generally changing the global climate system. Global climate models struggle to replicate the observed variability of the earth system after massive volcanic eruptions up to this point, and the reaction of the climate system to large volcanic eruptions is not fully understood. For geological periods, it has been proposed that volcanic ash influences climate in addition to the stratospheric climate forcing caused by volcanic sulphate aerosols by altering the global carbon cycle by fertilising the surface ocean with iron and promoting the growth of phytoplankton. Following the eruption of the volcano Kasatochi on the Aleutian Islands in the summer of 2008, this mechanism was also recently noticed. This review paper outlines the formation processes and atmospheric life cycles of volcanic sulphate and volcanic ash, contrasts their effects on climate, and highlights current gaps in our knowledge in order to spark further investigation into the impact of volcanic ash on the climate system via ocean iron fertilisation.

This article compares volcanic ash and mineral dust in terms of their sources, atmospheric loads, deposition mechanisms, atmospheric processing, and effects on the environment and climate. It also compares their chemical and physical properties. Although there are significant differences between the histories of volcanic ash and mineral dust particles before they are released into the atmosphere, there are many similarities between how the atmosphere is processed at ambient temperatures and the effects on the environment and climate. This review paper seeks to encourage future combined research methods to advance our existing understanding through close collaboration between mineral dust and volcanic ash experts by outlining the similarities and contrasts between the processes and consequences of volcanic ash and mineral dust.