Radiative Impacts and Stratospheric Loading from Increased Aerosol Emissions Due to an Increase in Satellite Re-entry Frequency.

The recent uptick in rocket launch rates, as well as the proposal of large low earth orbit satellite constellations (LLC’s) has renewed interest into how space traffic might impact Earth’s climate. One issue, the potential climate response to a significant increase in aerosols released into the lower mesosphere/upper stratosphere during satellite re-entry, remains under studied. The current annual mass flux from satellites vaporized in Earth’s middle atmosphere each year is ~0.4 Gg, well below the ~20 Gg/year natural mass emissions from meteor ablation. However, it is predicted that if all proposed LLC’s are implemented, the total number of satellites in low earth orbit (LEO) will balloon from ~5,000 to over 60,000 units. The corresponding annual emissions from satellite re-entry is also expected to increase and approach 10 Gg/yr. Little is currently known about what type of exotic aerosols may be released during satellite ablation, but a significant portion of the aerosol population may be metallic aluminum. Due to a slower descent speed, satellites will completely vaporize in the lower mesosphere meaning that pure aluminum could quickly fall into the stratosphere and become aluminum oxide (Al₂O₃). Past studies have shown how Al₂O₃ produced from aluminum aerosols released by solid rocket motors can impact stratospheric chemistry. However, very little work looking at the radiative impact from alumina aerosols in the stratosphere has been conducted. Here we present results from a study which focuses on the radiative impacts and atmospheric transport of hypothetical Al₂O₃ emissions from satellite re-entry. The WACCM6 global model coupled with the CARMA sectional model was run with a 10 Gg/year mass flux of alumina aerosol between 60 km and 70 km. We evaluate how aerosol size and latitude of emission may impact the overall transport, atmospheric burden, and radiative impacts from satellite re-entry.