Abstract
Abstract. During polar spring, the presence of reactive bromine in the polar boundary layer is considered to be the main cause of ozone depletion and mercury deposition. However, many uncertainties still remain regarding understanding the mechanisms of the chemical process and source of the bromine. As Arctic sea ice has recently been dramatically reduced, it is critical to investigate the mechanisms using more accurate measurements with higher temporal and spatial resolution. In this study, a typical process of enhanced bromine and depleted ozone in the Ny-Ålesund boundary layer in late April 2015 was observed by applying ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) technique. The results showed that there were bromine monoxide (BrO) slant columns as high as 5.6 × 1014 molec cm−2 above the Kings Bay area on 26 April. Meanwhile, the boundary layer ozone and gaseous elemental mercury (GEM) were synchronously reduced by 85 and 90 %, respectively. Based on the meteorology, sea ice distribution and air mass history, the sea ice in the Kings Bay area, which emerged for only a very short period of time when the enhanced BrO was observed, was considered to be the major source of this bromine enhancement event. The oxidized GEM may be directly deposited onto snow/ice and thereby influence the polar ecosystem.
Highlights
Bromine monoxide (BrO) is one of the key reactive halogen species that has profound impacts on the atmospheric chemistry of the polar boundary layer (PBL), especially the oxidative capacity of the troposphere (Saiz-Lopez and von Glasow, 2012)
Enhanced BrO was first detected by long-path differential optical absorption spectroscopy (LP-DOAS) observations (Platt, 1994)
From the GOME-2 BrO vertical column density (VCD) maps from 24 to 27 April (Fig. 10), we found that enhanced BrO was observed in the east of Greenland, far north of Siberia and east of Spitsbergen during the period of interest and in the days before
Summary
Bromine monoxide (BrO) is one of the key reactive halogen species that has profound impacts on the atmospheric chemistry of the polar boundary layer (PBL), especially the oxidative capacity of the troposphere (Saiz-Lopez and von Glasow, 2012). The presence of reactive bromine (in some situations called “bromine explosion”) is considered to be the main cause of the depletion of boundary layer ozone, known as “ozone depletion events” (ODEs) (Platt and Hönninger, 2003). The primary source of reactive bromine has been explained by a series of photochemical and heterogeneous reactions at the surface of the frozen ocean during polar spring (Fan and Jacob, 1992). Sea-ice (first year) surfaces, brine and frost flowers have been considered as possible sources (Kaleschke et al, 2004; Lehrer et al, 2004)
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