Abstract
Abstract. It is well known that during polar springtime halide sea salt ions, in particular Br-, are photochemically activated into reactive halogen species (e.g., Br and BrO), where they break down tropospheric ozone. This research investigated the role of blowing snow in transporting salts from the sea ice/snow surface into reactive bromine species in the air. At two different locations over first-year ice in the Ross Sea, Antarctica, collection baskets captured blowing snow at different heights. In addition, sea ice cores and surface snow samples were collected throughout the month-long campaign. Over this time, sea ice and surface snow Br- / Cl- mass ratios remained constant and equivalent to seawater, and only in lofted snow did bromide become depleted relative to chloride. This suggests that replenishment of bromide in the snowpack occurs faster than bromine activation in mid-strength wind conditions (approximately 10 m s−1) or that blowing snow represents only a small portion of the surface snowpack. Additionally, lofted snow was found to be depleted in sulfate and enriched in nitrate relative to surface snow.
Highlights
The polar springtime is a season of change, most notably in temperature, sea ice coverage, and weather, but it signals the onset of many photochemically driven atmospheric chemical reactions, such as tropospheric ozone depletion events (ODEs) (e.g., Barrie et al, 1988)
Raw anion concentrations for sea ice, surface snow, and blowing snow samples are provided in the Supplement
This work examined the mass ratio of Br−/Cl− in blowing snow during mid-strength winds to better understand mechanisms leading to bromine activation
Summary
The polar springtime is a season of change, most notably in temperature, sea ice coverage, and weather, but it signals the onset of many photochemically driven atmospheric chemical reactions, such as tropospheric ozone depletion events (ODEs) (e.g., Barrie et al, 1988). Boundary layer ozone in polar regions has been observed to fall dramatically periodically in the spring in both the Arctic (Barrie et al, 1988) and Antarctic (Kreher et al, 1997; Wessel et al, 1998) These tropospheric ODEs are initiated by increased concentrations of reactive bromine gases (BrO and Br) resulting in a catalytic removal of ozone (Fan and Jacob, 1992; McConnell et al, 1992; Frießet al., 2004); the mechanism by which Br enters the atmosphere is not well understood (Abbatt et al, 2012). The brine is expelled to the ice/snow or ice/atmosphere surface, where it forms a fractionated surface skim and slush (Rankin et al, 2002) This reservoir of bromide and other sea salts can be incorporated into frost flowers by wicking, or into the snow lying on sea ice by upward migration through capillary forces (Perovich and Richter-Menge, 1994). The physical surface at which bromide activation occurs remains a subject of some debate
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