Simulating glacial dust changes in the Southern Hemisphere using ECHAM6.3-HAM2.3

Mineral dust aerosol constitutes an important component of the Earth's climate system, not only on short timescales due to direct and indirect influences on the radiation budget but also on long timescales by acting as a fertilizer for the biosphere and thus affecting the global carbon cycle. For a quantitative assessment of its impact on the global climate, state-of-the-art atmospheric and aerosol models can be utilized. In this study, we use the ECHAM6.3-HAM2.3 model to perform global simulations of the mineral dust cycle for present-day (PD), pre-industrial (PI), and last glacial maximum (LGM) climate conditions. The intercomparison with marine sediment and ice core data, as well as other modeling studies, shows that the obtained annual dust emissions of 1221, 923, and 5159 Tg for PD, PI, and LGM, respectively, generally agree well with previous findings. Our analyses focusing on the Southern Hemisphere suggest that over 90 % of the mineral dust deposited over Antarctica are of Australian or South American origin during both PI and LGM. However, contrary to previous studies, we find that Australia contributes a higher proportion during the LGM, which is mainly caused by changes in the precipitation patterns. Obtained increased particle radii during the LGM can be traced back to increased sulfate condensation on the particle surfaces as a consequence of longer particle lifetimes. The meridional transport of mineral dust from its source regions to the South Pole takes place at different altitudes depending on the grain size of the dust particles. We find a trend of generally lower transport heights during the LGM compared to PI as a consequence of reduced convection due to colder surfaces, indicating a vertically less extensive Polar cell.

Automated summary

Mineral dust aerosol has a significant impact on the Earth's climate system, both on short timescales due to its influences on the radiation budget, and on long timescales by affecting the global carbon cycle. The study utilizes advanced models to simulate the global mineral dust cycle under different climate conditions and finds that Australia contributes more to the mineral dust deposition in Antarctica during the last glacial maximum (LGM), mainly due to changes in precipitation patterns. The increase in particle radii during the LGM is attributed to increased sulfate condensation on particle surfaces, resulting in longer particle lifetimes. The transport of mineral dust to the South Pole occurs at different altitudes depending on the grain size of the dust particles, and the LGM shows generally lower transport heights compared to pre-industrial (PI) conditions due to reduced convection.