Abstract: Measurements of e-folding depth, nadir reflectiv- ity and stratigraphy of the snowpack around Concordia sta- tion (Dome C, 75.10� S, 123.31� E) were undertaken to deter- mine wavelength dependent coefficients (350 nm to 550 nm) for light scattering and absorption and to calculate potential fluxes (depth-integrated production rates) of nitrogen dioxide (NO2) from the snowpack due to nitrate photolysis within the snowpack. The stratigraphy of the top 80 cm of Dome C snowpack generally consists of three main layers:- a sur- face of soft windpack (not ubiquitous), a hard windpack, and a hoar-like layer beneath the windpack(s). The e-folding depths are ~10 cm for the two windpack layers and ~20 cm for the hoar-like layer for solar radiation at a wavelength of 400 nm; about a factor 2–4 larger than previous model esti- mates for South Pole. The absorption cross-section due to impurities in each snowpack layer are consistent with a com- bination of absorption due to black carbon and HULIS (HU- mic LIke Substances), with amounts of 1–2 ng g-1 of black carbon for the surface snow layers. Depth-integrated photo- chemical production rates of NO2 in the Dome C snowpack were calculated as 5.3 × 1012 molecules m-2 s-1 , 2.3 × 1012 molecules m-2 s-1 and 8 × 1011 molecules m-2 s-1 for clear skies and solar zenith angles of 60�, 70� and 80� respectivelyusing the TUV-snow radiative-transfer model. Depending upon the snowpack stratigraphy, a minimum of 85 % of the NO2 may originate from the top 20 cm of the Dome C snow- pack. It is found that on a multi-annual time-scale photolysis can remove up to 80 % of nitrate from surface snow, con- firming independent isotopic evidence that photolysis is an important driver of nitrate loss occurring in the EAIS (East Antarctic Ice Sheet) snowpack. However, the model cannot completely account for the total observed nitrate loss of 90– 95 % or the shape of the observed nitrate concentration depth profile. A more complete model will need to include also physical processes such as evaporation, re-deposition or dif- fusion between the quasi-liquid layer on snow grains and firn air to account for the discrepancies.

Abstract: The passive tracer method is used to estimate ozone loss from ground-based measurements in the Antarctic. A sensitivity study shows that the ozone depletion can be estimated within an accuracy of ~4%. The method is then applied to the ground-based observations from Arrival Heights, Belgrano, Concordia, Dumont d'Urville, Faraday, Halley, Marambio, Neumayer, Rothera, South Pole, Syowa, and Zhongshan for the diagnosis of ozone loss in the Antarctic. On average, the ten-day boxcar average of the vortex mean ozone column loss deduced from the ground-based stations was about 55±5% in 2005–2009. The ozone loss computed from the ground-based measurements is in very good agreement with those derived from satellite measurements (OMI and SCIAMACHY) and model simulations (REPROBUS and SLIMCAT), where the differences are within ±3–5%.
The historical ground-based total ozone observations in October show that the depletion started in the late 1970s, reached a maximum in the early 1990s and stabilised afterwards due to saturation. There is no indication of ozone recovery yet. At southern mid-latitudes, a reduction of 20–50% is observed for a few days in October–November at the newly installed Rio Gallegos station. Similar depletion of ozone is also observed episodically during the vortex overpasses at Kerguelen in October–November and at Macquarie Island in July–August of the recent winters. This illustrates the significance of measurements at the edges of Antarctica.

Abstract: Background and aims – Despite the ongoing taxonomical revision of the entire (sub)-Antarctic diatom flora, our knowledge on the ecology and community associations of moss-inhabiting diatoms is still rather limited. In the present study, our research aim was to survey the diversity together with the environmental factors structuring the epiphytic moss diatom communities on Ile Amsterdam (TAAF), a small volcanic island in the southern Indian Ocean.Material and methods – A morphology-based dataset and (physico)chemical measurements were used for the ecological and biogeographical analysis of moss-inhabiting diatom flora from Ile Amsterdam. In total, 148 moss samples were examined using light microscopy.Key results – The analysis revealed the presence of 125 diatom taxa belonging to 38 genera. The uniqueness of the Ile Amsterdam diatom flora is mainly reflected by the species composition of the dominant genera Pinnularia, Nitzschia, Humidophila, and Luticola, with a large number of unknown and often new species. This highly specific diatom flora, together with differences in the habitats sampled and the isolated position of the island, resulted in very low similarity values between Ile Amsterdam and the other islands of the Southern Ocean. From a biogeographical point of view, 40% of the taxa have a typical cosmopolitan distribution, whereas 22% of all observed species can be considered endemic to Ile Amsterdam, with another 17% species showing a restricted sub-Antarctic distribution. The NMDS analysis, based on a cluster dendrogram, divides the samples into six main groups. For each group, indicator species were determined. Both environmental data and diatom distributions indicate that apart from elevation, specific conductance, pH, and moisture are the major factors determining the structure of moss-inhabiting diatom communities on Ile Amsterdam.Conclusion – The isolated geographic position and unique climatological and geological features of the island shaped the presence of a unique diatom flora, characterised by many endemic species. The results of the study are of prime importance for further (palaeo-)ecological and biogeographical research.