Diagnosing the controls on desert dust emissions through the Phanerozoic

Abstract. Desert dust is a key component of the climate system, as it influences Earth's radiative balance and biogeochemical cycles. It is also influenced by multiple aspects of the climate system, such as surface winds, vegetation cover, and surface moisture. As such, geological records of dust deposition or dust sources are important paleoclimate indicators; for example, dust records can be used to decipher aridity changes over time. However, there are no comprehensive records of global dust variations on tectonic time scales (10's of millions of years). Furthermore, although some modelling studies have focused on particular time periods of Earth's history, there has also been very little modelling work on these long timescales. In this study, we establish for the first time a continuous model-derived timeseries of global dust emissions over the whole Phanerozoic (the last 540 million years). We develop and tune a new offline dust emission model, DUSTY, driven by the climate model HadCM3L. Our results quantitatively reveal substantial fluctuations in dust emissions over the Phanerozoic, with high emissions in the Late Permian to Early Jurassic (×4 pre-industrial levels), and low emissions in the Devonian-Carboniferous (×0.1 pre-industrial levels). We diagnose the relative contributions from the various factors driving dust emissions and identify that the non-vegetated area plays a dominant role in dust emissions. The mechanisms of paleo hydrological variations, specifically the variations in low-precipitation-induced aridity, which primarily control the non-vegetated area, are then diagnosed. Our results show that paleogeography is the ultimate dominating forcing with the dust emissions variations explained by indices reflecting the land-to-sea distance of tropical and subtropical latitudes, whereas CO2 plays a marginal role. We evaluate our simulations by comparing them with sediment records and find fair agreement. This study contributes a quantified and continuous dust emission reconstruction, as well as an understanding of the mechanisms driving paleohydroclimate and dust changes over Earth's Phanerozoic history.