Abstract: Recovering a 1.5 million years record of climate and greenhouse gases from Antarctica is a major objective of the ice core community and there is an agreement that such "Oldest Ice" could be found in the plateau area of the East Antarctic Ice Sheet. The region around the permanent station of Concordia (East Antarctica) is among the few possible spots. In the framework of IPICS, it was decided to have a consortium to work on the reconnaissance for Oldest Ice in the region of Dome C. We present here the field measurements that are planned or already going on and how we plan to associate heterogenous observations and ice flow/thermal modelling to infer optimal location. The key issue for retrieving very old ice in central regions is to avoid zones with basal melting at the ice bed interface because this process removes basal layers. Modelling approach is a tool to make predictions about the thermal type of ice-bed interface as well as chronology of the deep layers, however it is limited by the badly known geothermal heat flux value and this approach has to be combined with field observations. The measurements we are considering are radar measurements (airborne, ground based, and pRES), relatively shallow drillings to measure temperature vertical profile and strain net survey.

Abstract: Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014–January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading to this isotopic composition.

Abstract: Maerl beds are among the most endangered habitats in coastal temperate waters and a priority for conservation. Passive acoustics is a potential non-intrusive approach for surveying this fragile ecosystem with minor disturbances. Invertebrate sounds can be major contributors to natural coastal soundscapes but are not well studied. We conducted controlled tank-based experiments to identify sound-producing invertebrates inhabiting north-east Atlantic maerl beds and to characterise their sounds in terms of frequency features and source levels. We also determined which sound types are able to be detected above natural maerl ambient noise and suitable for in situ monitoring. Tank recording sessions of 20 abundant and potentially soniferous invertebrates from maerl beds revealed eight soniferous species and 15 different sound types. Two new sound-producing families were identified, Calyptraeidae and Majidae. Six sound types had properties consistent with detectability and identification for in situ acoustic studies: the feeding sound of sea urchins Echinus esculentus, Paracentrotus lividus and Psammechinus miliaris, snapping sound of the snapping shrimp Athanas nitescens, and feeding and other sounds of the spider crab Maja brachydactyla. Estimated detection distances ranged from a few metres for sea urchin feeding sounds up to about 40 m for A. nitescens snaps and spider crab feeding sounds. These invertebrates, particularly A. nitescens, probably make a substantial contribution to the maerl ambient noise. This invertebrate sound library sets a basis for in situ acoustic studies.

Abstract: The French Kerguelen Archipelago represents an important breeding place for many species of marine top predators within the Southern Ocean, making the plateau hosting the archipelago and surrounding waters (CCAMLR area 58.5) a crucial area to design conservation measures.In this study, available tracking data from nine species of seabirds and marine mammals breeding at Kerguelen were analysed to define potential boundaries for a Marine Protected Area. Maps of time spent per square of each species were first used to describe high-use areas within the KerguelenPlateau. Habitat models were then developed for four species (Black-browed albatross, Wandering albatross,King penguin and Antarctic fur seal) chosen on the basis of their contrasted foraging ecology and diet to represent the top predator community. Predictive models were then applied to the main colonies of the four species for which no tracking data were available to illustrate the most important feeding areas at the scale of the entire study zone. An area delineated by the central part of the plateau and its slopes appeared to be of great importance for the toppredators’ community and would appropriately complete the limits of the existing Australian marine reserve of Heard and McDonald Islands.