Chemistry of the antarctic boundary layer and the interface with snow: an overview of the CHABLIS campaign

Abstract

Abstract. CHABLIS (Chemistry of the Antarctic Boundary Layer and the Interface with Snow) was a collaborative UK research project aimed at probing the detailed chemistry of the Antarctic boundary layer and the exchange of trace gases at the snow surface. The centre-piece to CHABLIS was the measurement campaign, conducted at the British Antarctic Survey station, Halley, in coastal Antarctica, from January 2004 through to February 2005. The campaign measurements covered an extremely wide range of species allowing investigations to be carried out within the broad context of boundary layer chemistry. Here we present an overview of the CHABLIS campaign. We provide details of the measurement location and introduce the Clean Air Sector Laboratory (CASLab) where the majority of the instruments were housed. We describe the meteorological conditions experienced during the campaign and present supporting chemical data, both of which provide a context within which to view the campaign results. Finally we provide a brief summary of highlights from the measurement campaign. Unexpectedly high halogen concentrations profoundly affect the chemistry of many species at Halley throughout the sunlit months, with a secondary role played by emissions from the snowpack. This overarching role for halogens in coastal Antarctic boundary layer chemistry was completely unanticipated, and the results have led to a step-change in our thinking and understanding.

DMS and MSA measurements in the Antarctic Boundary Layer: impact of BrO on MSA production

“…The measurements made by Preunkert et al, 2007 at DDU report constant average values of between 13 pptV in 2001 and 16 pptV in 2002 for June-October which are lower than those observed at Halley. Peaks in October and late November of up to 175 pptV are harder to attribute to exact sources, however at these times the wind speed around the continent reached 20 m/s (Jones et al, 2008), which is expected to enhance sea-air flux of this species from local areas of open water in addition to increasing the rate of transport from further north.…”

“…Aircraft avoided the Clean Air Sector according to protocol and routine access to the CASLab is by foot or by ski. Except for a small amount produced by the base there are no local sources of anthropogenic pollution and therefore measurements are dominated by long-range transport processes and oceanic emissions (Jones et al, 2008).…”

Investigating Local and Remote Terrestrial Influence on Air Masses at Contrasting Antarctic Sites Using Radon‐222 and Back Trajectories

“…Although some of the absolute differences between KSG and JBS can be attributed to atmospheric mixing depth, this has little impact on relative changes observed with wind speed. KSG experiences a marine‐like boundary layer year‐round (400–600 m; Chambers et al, ), whereas in summer JBS likely experiences mean mixing depths between 25 and 300 m (e.g., Angot et al, ; Jones et al, ; Parish & Bromwich, ). Another consideration is that activities of radium‐226 are ~70% higher in rock near KSG than around JBS (Evangelista & Pereira, ; Tositti et al, ), but there is more exposed ground in the vicinity of JBS than KSG (see Burton‐Johnson et al, ), and the rock is more weathered.…”

“…The corresponding distribution of wind speed was 1.4, 5.7, and 13.7 m s −1 . Making the broad assumptions that (i) all katabatic events have a similar fetch region, (ii) most radon is accumulated locally (i.e., low tropospheric radon concentrations, C TROP 0.05–0.1 Bq m −3 ), (iii) the highest wind speeds (shortest accumulation times) are associated with the lowest radon concentrations, and vice versa, and (iv) the mixing depth of the katabatic flow under the low‐wind‐speed summer conditions is ~50 m (Angot et al, ; Jones et al, ), we can attempt to constrain the coastal Antarctic radon source function.…”

Chemical Composition of Snow-Water and Scavenging Ratios over Costal Antarctica

“…Nitrate (NO 3 -) in polar snow is mainly due to the deposition of gaseous nitric acid , an acid that is the end product of the oxidation of various nitrogenous trace gases (NO x ). Jones et al, (2008) recorded the photochemical production of nitric oxide and nitrogen dioxide (NO and NO 2 ) in Antarctic snow cover. On the other hand NO 3 -has been found to be affected by post-depositional losses at locations of low accumulation (Röthlisberger et al, 2000).…”