The Importance of Blowing Snow to Antarctic Aerosols: Number Distribution and more than Source-Dependent Composition – results from the 2ODIAC campaign

Abstract

Abstract. A fundamental understanding of the processes that control Antarctic aerosols is necessary in determining thepresented here focus on the overall trends in aerosol composition primarily as functions of air masses and local meteorological conditions. The results suggest that air mass back trajectories have little impact on either the absolute or relative concentrations of the aerosol constituents measured by (and inferred from) an AMS at a coastal location. However, when the data is parsed 20 by wind speed, two observations become clear. First, a critical wind speed is required to loft snow from the surface, which, in turn, increases particle counts in all measured size bins. Second, this lofted (blowing) snow significantly increases both aerosol chloride and sodium. Further inspection of the AMS data shows that the increased chloride concentrations have distinctive signatures that differ from chloride measured at low wind speed. Also presented are the Cl:Na ratios of snow samples, aerosol filter samples, and non-chloride aerosol constituents measured by the AMS. Additionally, submicron aerosol iodine and 25 bromine concentrations as functions of wind speed are also presented. The results presented here suggest that aerosol composition in coastal Antarctica is a strong function of wind speed and that the mechanisms determining aerosol composition are likely linked to blowing snow.

Electric Phenomena as a Possible Driver of Polar Snow-air Interactions: Does this Factor Act Synergistically with Photoinduced Effects?

“…The appearance of the corona can lead to the formation of ozone, but after halogen (bromine) has transferred from the condensed phase to the gas phase as per the mechanism described above, all present ozone is destroyed. This type of ion transport mechanism may also explain changes in the ionic composition of snow during a blizzard [2]. Thus, if the corona is a "suspect" in our detective story, in one case it is "guilty" of increased ozone production during blizzards in polar regions far from the sea zone, and is also "guilty" of bromine emissions in the coastal zone and the resulting ozone destruction.…”

“…Most studies consider photochemistry to be the dominant mechanism of chemical transformations in the snow. However, some recent field data [1][2][3][4] cannot be interpreted in terms of the photochemical model alone. So, what other factors might play a role in snow-air interactions?…”

“…There is no doubt that one of them is the wind! The wind is known to change the ionic composition of snow [2], and to increase hydroxyl radicals [3] and ozone levels [4]. Conversely, wind events in the coastal zone sometimes stimulate the destruction of tropospheric ozone (ozone depletion events -ODE) by triggering a bromine emission, the so-called "bromine explosion" [5].…”