Abstract: Demographic parameters of wild animals are often closely associated with their foraging distribution and behaviour, and understanding these attributes can assist in identifying causes of population changes. The Indian Yellow-nosed Albatross (Thalassarche carteri) is endangered but little information is available on its at-sea distribution and behaviour. It breeds only in French (Iles Amsterdam, St Paul, Kerguelen and Crozet) and South African (Prince Edward Island, PEI) territories in the south-west Indian Ocean, with PEI supporting about 20% of the global population. This study aimed to investigate the at-sea distributions of adult Indian Yellow-nosed Albatrosses provisioning chicks at PEI and to compare them with distributions of Yellow-nosed Albatrosses breeding at other localities. Using satellite transmitters, we identified two areas that were particularly favoured for foraging. Parents whose partners were brooding small chicks frequently moved north-east of PEI to shallow, productive waters where cold, nutrient-rich water upwells and results in enhanced levels of chlorophyll-a. By contrast, parents with older chicks that could be left unattended often foraged along the Agulhas Bank where eddies and shear forces promote vertical mixing. The at-sea distribution of birds breeding at PEI was located between those reported for Indian Yellow-nosed Albatrosses breeding at Ile Amsterdam and Atlantic Yellow-nosed Albatrosses (T. chlororhynchos) breeding at Gough Island, so that birds from these localities may face different threats at sea. Our study is the first to highlight key feeding areas for Indian Yellow-nosed Albatrosses from PEI and to demonstrate partitioning of foraging grounds by Yellow-nosed Albatrosses from different localities.

Abstract: To fully decipher the role of nitrate photolysis on the atmospheric oxidative capacity in snow-covered regions, NOx flux must be determined with more precision than existing estimates. Here, we introduce a method based on dynamic flux chamber measurements for evaluating the NOx production by photolysis of snowpack nitrate in Antarctica. Flux chamber experiments were conducted for the first time in Antarctica, at the French-Italian station Concordia, Dome C (75°06'S, 123°20’E, 3233 m a.s.l) during the 2019–2020 summer campaign. Measurements were gathered with several snow samples of different ages ranging from newly formed drifted snow to 6-year-old firn. Contrary to existing literature expectations, the daily average photolysis rate coefficient, , did not significantly vary between differently aged snow samples, suggesting that the photolabile nitrate in snow behaves as a single-family source with common photochemical properties, where a = (2.37 0.35) × 10−8 s−1 (1) has been calculated from December 10th 2019 to January 7th 2020. At Dome C summer daily average NOx flux, , based on measured NOx production rates was estimated to be (4.3 1.2) × 108 molecules cm−2 s−1, which is 1.5–7 times less than the net NOx flux observed previously above snow at Dome C using the gradient flux method. Using these results, we extrapolated an annual continental snow sourced NOx budget of 0.017 0.003 TgN y−1, 2 times the nitrogen budget, (N-budget), of the stratospheric denitrification previously estimated for Antarctica. These quantifications of nitrate photolysis using flux chamber experiments provide a road-map toward a new parameterization of the product that can improve future global and regional models of atmospheric chemistry.

Abstract: Thanks to its long duration, the Rosetta mission has provided a unique insight into the properties of dust particles released by 67P/C-G nucleus, and ascertained the links between cometary dust and CP-IDPs or UCAMMs [1]. Minerals to organics proportions are quite comparable within the refractory phase, in which carbon-bearing compounds present high-molecular masses [2-4]. Dust particles consist of aggregates of smaller grains and present hierarchical structures, with morphologies ranging from extremely porous to almost compact [5-7]. The refractory materials released in comae (monitored with ≈ 4-1.2 au solar distance range for 67P/C-G), subjected to gravitational and non-gravitational forces, build up dust tails and trails, and progressively become parts of the zodiacal cloud, i.e. the lenticular-shaped interplanetary dust cloud. The small dust particles spiral towards the Sun under Poynting-Robertson effect, with migration times in the 300-50000 years range for micron-sized grains with densities about 100-1000 kg m-3 released at solar distances about 4-1.2 au [8]. Such dust particles happen to encounter the Earth atmosphere. Independent approaches have established that most of the near-Earth interplanetary dust comes from Jupiter Family comets, such as 67P/C-G [9-11], which orbit in the vicinity of the ecliptic plane. Updates of our present understanding of dust in 67P/C-G will be proposed. Through various numerical and experimental simulations [e.g. 12], the changes in composition and in physical properties of cometary dust particles in the interplanetary dust cloud will be discussed, as a function of time and of solar distance. The possible implications, for the early evolution of terrestrial planets, of the properties of the cometary dust component in the interplanetary dust cloud will be tentatively addressed. 1. Levasseur-Regourd et al. SSR 2018. 2. Goesmann et al. Science 2015. 3. Fray et al. Nature 2016. 4. Bardyn et al. MNRAS 2017. 5. Bentley et al. Nature 2016. 6. Langevin et al. Icarus 2016. 7. Mannel et al. MNRAS 2017. 8. Saïagh PhD Thesis UPE 2014. 9. Lasue et al. Astron. Astrophys. 2007. 10. Nesvorny et al. ApJ 2010. 11. Rowan-Robinson and May MNRAS 2013. 12. Hadamcik et al. PSS 2018.