Past and Future Changes in African Dust-Favourable Atmospheric Circulation over Iberia

Large-scale atmospheric circulation exerts a primary control on environmental variability over the western Mediterranean, where African dust outbreaks strongly affect aerosol loading, radiative balance, air quality, and ecosystem dynamics. Although recent decades have shown substantial interannual variability in African dust transport towards Iberia and the Mediterranean Basin, uncertainties remain regarding the long-term evolution of dust-favourable synoptic conditions under climate change. Here we investigate the past, present, and future evolution of atmospheric circulation regimes associated with African dust outbreaks using a multi-source framework that combines reanalysis datasets, CMIP6 climate simulations, observational dust records, and sedimentary archives.

Daily atmospheric circulation states were characterised using 850 hPa geopotential height fields over North Africa and the western Mediterranean. We applied a fixed-centroid weather-regime classification consistently across modern reanalyses, long-term historical reconstructions, and climate model simulations. The classification identifies 11 recurrent synoptic circulation regimes, of which 6 are significantly associated with enhanced African dust transport towards Iberia and the western Mediterranean (Salvador et al, 2022). Dust relevance was validated using independent observational datasets, including satellite-constrained aerosol products and observational catalogues of African dust outbreaks over the Iberian Peninsula.

To extend the analysis beyond the satellite and modern observational period, we incorporated long-term reanalysis products such as the NOAA 20th Century Reanalysis, allowing reconstruction of circulation variability back to the 19th century. This enabled us to assess whether the recent increase in dust-favourable circulation patterns is unprecedented within the context of the last ~200 years, and to evaluate multidecadal variability linked to large-scale modes of atmospheric circulation. We further compared these reconstructed circulation trends with historical simulations from CMIP6 models.

Multi-model ensembles are then used to assess future changes under SSP1-2.6 to SSP5-8.5 scenarios. Preliminary results show that dust-related circulation regimes represent ~58% of days in the historical baseline period (1980–2014). Both ERA5 and the CMIP6 historical ensemble show positive trends in dust-favourable circulation occurrence (~+0.69% and +0.67% per decade, respectively). Future projections indicate a robust intensification of these conditions throughout the 21st century, particularly under high-emission scenarios. Under SSP5-8.5, trends reach nearly +1.94% per decade, suggesting a substantial increase in the persistence and recurrence of atmospheric configurations conducive to African dust transport. Results also indicate a seasonal expansion of dust-conducive circulation into spring months.

Additionally, we intend to explore the feasibility of using sedimentary evidence of African dust deposition in lacustrine archives from the Iberian Peninsula and the Pyrenees. These high-resolution sediment records may provide an independent paleoclimatic benchmark to evaluate the realism of reconstructed atmospheric circulation and inferred dust variability over longer timescales. Ongoing analyses include hyperspectral imaging, geochemical tracers, and mineralogical indicators associated with North African dust inputs. By integrating atmospheric dynamics, climate model simulations, historical reanalyses, and sedimentary evidence, this work aims to improve the diagnosis and long-term understanding of extreme aerosol transport events in a changing climate and to provide a more robust framework for evaluating future dust-related hazards in the Mediterranean region.