Abstract: Coloniality is associated with various benefits and costs for animals affecting their fitness. Breeding colonies are heterogeneous both in terms of physical and social parameters, thus, breeding territories are of different quality relative to their location within the colony. In king penguins, increased conspecific density has been correlated with increased stress level in individual birds, suggesting a cost of colonial breeding. We used a cross-fostering approach to question the relationship linking breeding location, phenotype and reproduction success. We crossfostered eggs shortly after laying within and between high-and low-density colony areas. This design allowed us to unravel the influences of early genetic and maternal effects together with rearing environments on chick growth trajectories, stress physiology and survival. We tested whether chick phenotype is determined at birth to match their early environment or if higher social density conferred an advantage for reproduction.

Abstract: Secondary microseisms are ubiquitous ambient noise vibrations due to ocean activity, dominating worldwide seismographic records at seismic periods between 3 and 10 s. Their origin is a heterogeneous distribution of pressure fluctuations along the ocean surface. In spherically symmetric earth models, no Love surface waves are generated by such a distributed surface source. We present global-scale modelling of three-component secondary microseisms using a spectral-element method, which naturally accounts for a realistic distribution of surface sources, topography and bathymetry, and 3-D heterogeneity in Earth’s crust and mantle. Seismic Love waves emerge naturally once the system reaches steady state. The ergodic origin of Love waves allows us to model the horizontal components of secondary microseisms for the first time. Love waves mostly originate from the interaction of the seismic wavefield with heterogeneous Earth structure in which the mantle plays an important role despite the short periods involved. Bathymetry beneath the source region produces weak horizontal forces that are responsible for a weak and diffuse Love wavefield. The effect of bathymetric force splitting into radial and horizontal components is overall negligible when compared to the effect of 3-D heterogeneity. However, we observe small and well-focused Love-wave arrivals at seismographic stations in Europe due to force splitting at the steepest portion of the North Atlantic Ridge and the ocean–continent boundary. The location of the sources of Love waves is seasonal at periods shorter than about 7 s, while seasonality is lost at the longer periods. Sources of Rayleigh and Love waves from the same storm may be located very far away, indicating that energy equipartitioning might not hold in the secondary microseism period band.

Abstract: Dans un contexte de changement climatique, il est important de déterminer avec précision l’évolution actuelle et future des processus environnementaux pouvant avoir un impact sur les populations. Ainsi, connaitre l’évolution saisonnière du couvert neigeux s’avère crucial car c’est une composante du cycle de l’eau, jouant un rôle de stockage au printemps. La télédétection spatiale joue un rôle important pour le suivi de l’évolution du manteau neigeux aux échelles continentale et régionale. Des études ont déjà mis en avant certains avantages du radar en bande X (notamment son signal de phase). L’analyse du lien entre la réponse de plusieurs paramètres polarimétriques (K0, K3, K4, K7, CCOH et le CPD) et des données météorologiques (dont l’épaisseur du manteau), a permis de conforter l’utilité de la bande X pour la cible neige. On note un intérêt pour l’intensité totale (K0) qui s’avère être intéressante pour l’étude de la hauteur totale de neige. La différence de phase (CPD), ne s’avère pas concluante pour retracer l’épaisseur totale du manteau neigeux dans notre cas d’application. En revanche, elle offre un bon diagnostic des chutes de neige fraiche et pour la cartographie du métamorphisme de la neige.

Abstract: Strong large-scale winds can relay their energy to the ocean bottom and elicit an almost immediate intraseasonal barotropic (depth independent) response in the ocean. The intense winds associated with the Madden-Julian Oscillation over the Maritime Continent generate significant intraseasonal basin-wide barotropic sea level variability in the tropical Indian Ocean. Here we show, using a numerical model and a network of in-situ bottom pressure recorders, that the concerted barotropic response of the Indian and the Pacific Ocean to these winds leads to an intraseasonal see-saw of oceanic mass in the Indo-Pacific basin. This global-scale mass shift is unexpectedly fast, as we show that the mass field of the entire Indo-Pacific basin is dynamically adjusted to Madden-Julian Oscillation in a few days. We find this large-scale ocean see-saw, induced by the Madden-Julian Oscillation, has a detectable influence on the Earth’s polar axis motion, in particular during the strong see-saw of early 2013.

Abstract: Marine litter has become a global issue with ‘garbage patches’ documented in all ocean gyres. The Pacific and Atlantic garbage patches have been well described, but there are few empirical data for the Indian Ocean. In the austral summer 2019–2020, we conducted an at-sea survey of macro-litter in the rarely investigated south-west Indian Ocean. Over 24 days, 1623 man-made items were observed including plastic fragments, packaging and fishing-related items during 216 h of observations covering 5464 km. More than 99% of the litter items were plastics of which almost 60% were white. Floating litter was patchily distributed with only five items (0.2%) recorded south of 40°S (0.1 items·km‐2). Half of the items were encountered over a two-day period south-east of Madagascar (30°S; 59–67°E; 75.2 items·km‐2). Our survey detected an accumulation of litter in the southern Indian Ocean and demonstrated that this area warrants more research.