At just over 4000 m above sea level, Dome Argus is the highest ice mountain in Antarctica and among the coldest places on Earth. On 10 July 2017, China’s weather station there recorded a temperature of −78.9°C. When dense frigid air presses down on Dome Argus and other high points in the continent’s interior, it flows downslope. By the time the air reaches the coast, it’s blowing as a fierce, near-constant wind.

The wind sweeps up snow and sends it hundreds of meters into the air. From space, the drifting snow, which can extend for thousands of kilometers, resembles clouds. Some clouds affect Earth’s radiative budget by reflecting sunlight back into space and trapping outgoing radiation in the lower atmosphere. Does drifting snow have the same effect? According to a newly published study by Stefan Hofer of the University of Oslo in Norway and his collaborators, the answer is not quite.

The main reason to suspect a difference between clouds and drifting snow is sublimation. The prevailing winds in Antarctica are so dry and so strong that they turn ice crystals into water vapor. The increase in humidity and the expenditure of thermal energy to drive sublimation could conceivably be substantial. Colder and damper, the air within a snow drift could conceivably form additional clouds.

To quantify drifting snow’s effects on Antarctica’s climate, Hofer and his collaborators yoked two models together. One model, the Modèle Atmosphérique Régional (MAR), calculates the radiative budget at different levels in a one-dimensional atmosphere that includes water in the forms it takes in polar regions, including ice crystals and snow particles. The other model, Soil Ice Snow Vegetation Atmosphere Transfer (SISVAT), calculates conditions along a 1D surface and feeds them into MAR. The researchers ran the combined models with and without drifting snow.

Comparing the two runs revealed that the effects of drifting snow are various and significant. For example, in the continent’s interior, drifting snow decreases the temperature of the lowest 500 m of the atmosphere by 0.66 ± 0.4 °C. Overall, the run that included drifting snow produced 18.6% more cloud coverage over Antarctica than the run without drifting snow.

As for the radiative budget, the additional, snowdrift-induced clouds both reflect more sunlight and trap more heat. The latter effect is stronger, and the net effect is to increase the radiative power, or forcing, at the surface by 2.7 W/m². Although that positive forcing occurs only where there’s drifting snow, it’s about the same in magnitude as that of all the greenhouse gases and aerosols averaged over the planet. (S. Hofer et al., Geophys. Res. Lett., 2021, doi-10.1029/2021GL094967.)