Influence of Dust on the Initiation of Neoproterozoic Snowball Earth Events

Abstract

AbstractIt has been demonstrated previously that atmospheric dust loading during the Precambrian could have been an order of magnitude higher than in the present day and could have cooled the global climate by more than 10 °C. Here, using the fully coupled atmosphere-ocean general circulation model CESM1.2.2, we determine whether such dust loading could have facilitated the formation of Neoproterozoic snowball Earth events. Our results indicate global dust emission decreases as atmospheric CO2 concentration (pCO2) decreases due to increasing snow coverage, but atmospheric dust loading does not change or even increases due to decreasing precipitation and strengthening June-July-August (JJA) Hadley circulation. The latter lifts more dust particles to high altitude and thus increases the lifetime of these particles. As the climate becomes colder and the surface albedo higher, the cooling effect of dust becomes weaker; when the global mean surface temperature is approximately -13 °C, dust has negligible cooling effect. The threshold pCO2 at which Earth enters a snowball state is between 280 to 140 ppmv when there is no dust, and is similar when there is relatively light dust loading (~4.4 times present-day value). However, the threshold pCO2 decreases dramatically to between 70 to 35 ppmv when there is heavy dust loading (~33 times present-day value), due to the decrease in planetary albedo which increases the energy input into the climate system. Therefore, dust makes it more difficult for Earth to enter a snowball state.