Articles | Volume 15, issue 13
Research article
13 Jul 2015
Research article |  | 13 Jul 2015

The role of blowing snow in the activation of bromine over first-year Antarctic sea ice

R. M. Lieb-Lappen and R. W. Obbard

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.

Short summary
This work analyzes the chemical composition of blowing snow collected over first-year Antarctic sea ice to assess its role in bromine activation during the polar sunrise. We found lofted snow to be depleted in Br- relative to Cl- by proportionally increasing amounts with height. This is the first study to use field data to substantiate modeling results implicating blowing snow as the location for initial halogen activation. We also found lofted snow to be depleted in SO4 and enriched in NO3.
Final-revised paper