Inter-annual variability of surface ozone at coastal (Dumont d'Urville, 2004–2014) and inland (Concordia, 2007–2014) sites in East Antarctica

Abstract

Abstract. Surface ozone has been measured since 2004 at the coastal East Antarctic site of Dumont d'Urville (DDU), and since 2007 at the Concordia station located on the high East Antarctic plateau. This paper discusses long-term changes, seasonal and diurnal cycles, as well as inter-annual summer variability observed at these two East Antarctic sites. At Concordia, near-surface ozone data were complemented by balloon soundings and compared to similar measurements done at the South Pole. The DDU record is compared to those obtained at the coastal site of Syowa, also located in East Antarctica, as well as the coastal sites of Neumayer and Halley, both located on the coast of the Weddell Sea in West Antarctica. Surface ozone mixing ratios exhibit very similar seasonal cycles at Concordia and the South Pole. However, in summer the diurnal cycle of ozone is different at the two sites with a drop of ozone in the afternoon at Concordia but not at the South Pole. The vertical distribution of ozone above the snow surface also differs. When present, the ozone-rich layer located near the ground is better mixed and deeper at Concordia (up to 400 m) than at the South Pole during sunlight hours. These differences are related to different solar radiation and wind regimes encountered at these two inland sites. DDU appears to be the coastal site where the impact of the late winter/spring bromine chemistry is the weakest, but where the impact of elevated ozone levels caused by NOx snow emissions from the high Antarctic plateau is the highest. The highest impact of the bromine chemistry is seen at Halley and Neumayer, and to a lesser extent at Syowa. These three sites are only weakly impacted by the NOx chemistry and the net ozone production occurring on the high Antarctic plateau. The differences in late winter/spring are attributed to the abundance of sea ice offshore from the sites, whereas those in summer are related to the topography of East Antarctica that promotes the katabatic flow bringing oxidant-rich inland air masses to the site. There appears to be a decreasing change in summer surface ozone at the two East Antarctic sites of Concordia and DDU over the most recent period (2004–2014 and 2007–2014). Further research, including continued monitoring, is needed at these two sites to better separate the effect of synoptic transport from possible change of NOx snow emissions in response to recovery of the stratospheric ozone layer leading to penetration of more UV radiation to the surface.

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

“…Snowpack is not a location of ozone production: Ozone in snowpack interstitial air is generally depleted compared to above the surface (Albert et al, 2002;Bocquet et al, 2007;Helmig, Bocquet, et al, 2007;Peterson & Honrath, 2001;Seok et al, 2015), and ozone is always destroyed in snow chamber experiments (Aldaz, 1969;Bottenheim et al, 2002). However, ozone production in the poorly mixed layer right above snow may occur following the accumulation of ozone precursor emissions from the snowpack and enhanced irradiance from snow (e.g., Crawford et al, 2001;Cristofanelli et al, 2018;Helmig et al, 2008;Legrand et al, 2009Legrand et al, , 2016. 4.6.1.…”

Year-round record of near-surface ozone and O<sub>3</sub> enhancement events (OEEs) at Dome A, East Antarctica

“…During non-polar night, the concentration of near-surface ozone at the SP was approximately 3 ppb 235 higher than that at DA, and the concentrations at the SP are similar to those at the Concordia Station (e.g., Legrand et al, 2016;Cristofanelli et al, 2018…”

Reactive bromine in the low troposphere of Antarctica. Estimations at two research sites

“…7) and is typical of remote, low NOx environments with O3 being accumulated during winter (maximum) and destroyed (minimum) during summer. Also, the observed amplitude of the surface O3 annual cycle at both stations were also characteristic of an Antarctic station (e.g., Helmig et al, 2007, Legrand et al, 2016. While in 2015 the median values of surface O3 were quite similar at both locations (23 nmol mol -1 at Marambio and 24 nmol mol -1 at 35 Belgrano), the maximum values reported at Marambio (36.8 nmol mol -1 ) were about a 10 % higher than those observed at Belgrano station.…”