Abstract:

Abstract. Polar stratospheric clouds (PSCs) play a critical role in the stratospheric ozone depletion processes. The last 30 years have seen significant improvements in our understanding of the PSC processes but PSC parametrization in global models still remains a challenge due to the necessary trade-off between the complexity of PSC microphysics and model parametrization constraints. The French Antarctic station Dumont d'Urville (DDU, 66.6^∘ S, 140.0^∘ E) has one of the few high latitude ground-based lidars in the Southern Hemisphere that has been monitoring PSCs for decades. This study focuses on the PSC data record during the 2007–2020 period. First, the DDU lidar record is analysed through three established classification schemes that prove to be mutually consistent: the PSC population observed above DDU is estimated to be of 30 % supercooled ternary solutions, more than 60 % nitric acid trihydrate mixtures and less than 10 % of water–ice dominated PSC. The Cloud–Aerosol Lidar with Orthogonal Polarization PSC detection around the station are compared to DDU PSC datasets and show a good agreement despite more water–ice PSC detection. Detailed 2015 lidar measurements are presented to highlight interesting features of PSC fields above DDU. Then, combining a temperature proxy to lidar measurements, we build a trend of PSC days per year at DDU from ERA5 (the fifth generation of European ReAnalysis) and NCEP (National Centers for Environment Protection reanalysis) reanalyses fitted on lidar measurements operated at the station. This significant 14-year trend of −4.6 PSC days per decade is consistent with recent temperature satellite measurements at high latitudes. Specific DDU lidar measurements are presented to highlight fine PSC features that are often sub-scale to global models and spaceborne measurements.

Abstract: The major histocompatibility complex (MHC) plays a crucial role in the resistance to parasites in vertebrates and is thus often suggested to be an important force driving social interactions, including mating preference. However, the phenotypic cues used by individuals to assess the MHC characteristics of conspecifics are generally unknown. Here, we used behavioral tests to investigate whether, in black-legged kittiwakes, females use odor cues to distinguish male MHC-II diversity and MHC-II dissimilarity. We found that females took less time to peck at an odor sample coming from a male with high or low MHC-II diversity compared to intermediate MHC-II diversity. However, this result is due to the single individual who has only one MHC-II allele. When excluding this individual, females took less time to peck at an odor sample coming from a male with high MHC-II diversity. In addition, when the odor sample came from a male with higher MHC-II dissimilarity, females took less time to peck at the sample, but once they pecked at it, they delayed the use of the sample. Altogether, our results add evidence for olfactory recognition of MHC characteristics in birds, but further studies are needed to determine whether kittiwakes use this ability to optimize fitness.

Abstract: In the Southern Hemisphere, the prevalence of oceans and the difficulty of access to land result in reduced coverage of seismological stations, limiting our detailed knowledge of Earth’s structures and of large earthquakes sources. This situation is exacerbated inside the antarctic continent, where only two permanent seismic stations are currently available (IU.QSPA at South Pole and G.CCD). The CCD station, built in early 2000s with state‐of‐the‐art surface instrumentation and located at the French–Italian Concordia base (75° S, 123° E), has been providing seismological data since 2008. However, it suffers from several problems: the vault is deformed by the hydrostatic pressure of the snow, the firn waveguide traps anthropogenic noise from the base causing strong noise below 1 s, and a coupling defect limits the performance above 30 s on the horizontal channels. To ensure the continuity of CCD and to improve its overall performance, we started in 2014 to plan the installation of a borehole seismometer at the site. In this article, we describe in detail this renovation of CCD and some examples of data analysis. The new borehole sensor shows that short‐period disturbances are largely attenuated (−20 dB at 0.1 s) compared to the surface installation and that the horizontal channels have a lower noise level at long periods (−8 dB at 100 s). Data for all components are below the standard noise model between 0.1 and 0.2 s, which makes this sensor one of the quietest installations in the world for this bandwidth. For periods >600 s we observe atmospheric pressure‐related perturbations on the vertical component. Despite this problem, the new CCD borehole station is a success with better‐than‐expected performances at all periods <600 s. The data produced are now distributed in the world’s data centers as G.CCD.20 and we encourage the scientific community to use the data for all studies requiring seismograms from Antarctica.

Abstract: A destructive earthquake (Mw 6.1) struck Pasaman, West Sumatra, Indonesia, on 25 February 2022, resulting in at least 18 deaths and damage to 1765 buildings. Our relocated foreshock, mainshock, and aftershocks and their source mechanisms reveal a previously unknown ∼20 km long segment of the Sumatran Fault as a result of dextral strike-slip motion (strike N132oE and dip 72oSW) along what we have called the Kajai Fault. The inverted rupture model indicates a single, compact asperity with an approximate depth range of 2–11 km. This asperity extends ∼14 km along strike, and ∼9 km in the down-dip direction. The Coulomb stress change of the mainshock shows that areas to the north and south experienced an increase in stress, which is consistent with the observed aftershock pattern. The nearby Great Sumatran Fault segments (Angkola and Sumpur) experienced a significant increase in stress without any accompanying aftershocks, which likely increases the risk of them rupturing in the future.

Abstract: Les îles subantarctiques de Kerguelen sont soumises à un changement climatique rapide et intense. Ces îles abritent des espèces végétales endémiques de grand intérêt dans l’hémisphère sud. La flore comporte peu d’espèces et leurs interactions sont mal connues. De tels systèmes pourraient être particulièrement fragiles, et a contrario leur résilience dépendre plus fortement des interactions biotiques entre espèces. Le projet PlantADAPT vise à évaluer et suivre la réponse des espèces de plantes endémiques des îles Kerguelen au changement climatique, en prenant en compte le système plante-sol intégré et les interactions biotiques (plante holobionte). Dans l’objectif d’évaluer les parts respectives de la plasticité phénotypique et de l’adaptation locale dans la variation phénotypique, l’expérience en Jardins Communs est un dispositif déterminant. Nous développons aussi des approches d’écologie fonctionnelle des communautés microbiennes et du système sol associé.