A Rapid Pathway for Saharan Dust Transport to the Arctic

A new pathway for Saharan dust transport to the Arctic is found recently^[1,2], crossing the North Atlantic directly into the Arctic. In order to reveal the climatology features of this rapid pathway, Merra-2, ERA5 reanalysis data and Geos-Chem model simulations are used in this study. We started our analysis with a dust enhancement case study. From model simulations, on 14 March 2022, a Saharan dust event is transported northwards. This dust took only a few days to reach the Arctic along this pathway. In the following month, there were four dust enhancement events. Model results indicate that the Shahara Desert is the main source (~ 80%) of Arctic dust in spring. From Merra-2 reanalysis data (dust aerosol optical depth, AOD), this new pathway once opened from 2000 to 2015, and then closed until 2022. Combined with the North Atlantic Oscillation (NAO) index and the ERA5 reanalysis data (700 hPa wind field), we find that the opening of the rapid pathway tends to be in the weakly positive or negative phase of the NAO. It implies that the jet stream is more meandering, which is favorable for dust transport. Specifically, the opening of the rapid pathway requires the presence of cyclones in the residual circulation near Iceland and anticyclones in the mid-latitude Atlantic.

 

Reference

[1] Francis, D., Eayrs, C., Chaboureau, J.-P., Mote, T., & Holland, D. M. (2018). Polar jet associated circulation triggered a Saharan cyclone and derived the poleward transport of the African dust generated by the cyclone. Journal of Geophysical Research: Atmospheres, 123, 11,899–11,917. https://doi.org/10.1029/2018JD029095

[2] Francis, D., Mattingly, K. S., Lhermitte, S., Temimi, M., and Heil, P.: Atmospheric extremes caused high oceanward sea surface slope triggering the biggest calving event in more than 50 years at the Amery Ice Shelf, The Cryosphere, 15, 2147–2165, https://doi.org/10.5194/tc-15-2147-2021, 2021.