Bigot-Sazy M-A, Charlassier R, Hamilton J-Ch, Kaplan J, Zahariade G, . (2013). Self-calibration: an efficient method to control systematic effects in bolometric interferometry
. ASTRONOMY & ASTROPHYSICS, 550(A), 59.
Abstract: Context. The QUBIC collaboration is building a bolometric interferometer dedicated to the detection of B-mode polarization fluctuations in the cosmic microwave background.
Aims: We introduce a self-calibration procedure related to those used in radio-interferometry to control a wide range of instrumental systematic errors in polarization-sensitive instruments.
Methods: This procedure takes advantage of the need for measurements on redundant baselines to match each other exactly in the absence of systematic effects. For a given systematic error model, measuring each baseline independently therefore allows writing a system of nonlinear equations whose unknowns are the systematic error model parameters (gains and couplings of Jones matrices, for instance).
Results: We give the mathematical basis of the self-calibration. We implement this method numerically in the context of bolometric interferometry. We show that, for large enough arrays of horns, the nonlinear system can be solved numerically using a standard nonlinear least-squares fitting and that the accuracy achievable on systematic effects is only limited by the time spent on the calibration mode for each baseline apart from the validity of the systematic error model.
Programme: 915
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Bernard É, Friedt JM, Saintenoy A, Tolle F, Griselin M, Marlin C, . (2014). Where does a glacier end? GPR measurements to identify the limits between valley slopes and actual glacier body. Application to the Austre Lovénbreen, Spitsbergen . International Journal of Applied Earth Observation and Geoinformation, 27, Part A(A), 100–108.
Keywords: Ground penetrating Radar, Glacier limit, Arctic, Spitsbergen, Polar glacier,
Programme: 1108,1111
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Labrousse Sara, Vacquié-Garcia Jade, Heerah Karine, Guinet Christophe, Sallée Jean-Baptiste, Authier Matthieu, Picard Baptiste, Roquet Fabien, Bailleul Frédéric, Hindell Mark, Charrassin Jean-Benoit, . (2015). Winter use of sea ice and ocean water mass habitat by southern elephant seals: The length and breadth of the mystery
. Prog. Oceanogr., 137(A), 52–68.
Abstract: Understanding the responses of animals to the environment is crucial for identifying critical foraging habitat. Elephant seals (Mirounga leonina) from the Kerguelen Islands (49°20′S, 70°20′E) have several different foraging strategies. Why some individuals undertake long trips to the Antarctic continent while others utilize the relatively close frontal zones is poorly understood. Here, we investigate how physical properties within the sea ice zone are linked to foraging activities of southern elephant seals (SES). To do this, we first developed a new approach using indices of foraging derived from high temporal resolution dive and accelerometry data to predict foraging behaviour in an extensive, low resolution dataset from CTD-Satellite Relay Data Loggers (CTD-SRDLs). A sample of 37 post-breeding SES females were used to construct a predictive model applied to demersal and pelagic dive strategies relating prey encounter events (PEE) to dive parameters (dive duration, bottom duration, hunting-time, maximum depth, ascent speed, descent speed, sinuosity, and horizontal speed) for each strategy. We applied these models to a second sample of 35 seals, 20 males and 15 females, during the post-moult foraging trip to the Antarctic continental shelf between 2004 and 2013, which did not have fine-scale behavioural data. The females were widely distributed with important foraging activity south of the Southern Boundary Front, while males predominately travelled to the south-eastern part of the East Antarctica region. Combining our predictions of PEE with environmental features (sea ice concentration, water masses at the bottom phase of dives, bathymetry and slope index) we found higher foraging activity for females over shallower seabed depths and at the boundary between the overlying Antarctic Surface Water (AASW) and the underlying Modified Circumpolar Deep Water (MCDW). Increased biological activity associated with the upper boundary of MCDW, may provide overwintering areas for SES prey. Male foraging activity was strongly associated with pelagic dives within the Antarctic Slope Front where upwelling of nutrient rich Circumpolar Deep Water onto surface water may enhance and concentrate resources. A positive association between sea ice and foraging activity was found for both sexes where increased biological activity may sustain an under-ice ecosystem. Variability of the East Antarctic sea ice season duration is likely a crucial element to allow air-breathing predators to benefit from profitable prey patches within the pack ice habitat.
Programme: 109
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Ricaud P, Carminati F, Attié J-L, Courcoux Y, Rose T, Genthon C, Pellegrini A, Tremblin P, August T, . (2013). Quality Assessment of the First Measurements of Tropospheric Water Vapor and Temperature by the HAMSTRAD Radiometer Over Concordia Station, Antarctica
. 0196-2892, PP(99), 1–23.
Abstract: The HAMSTRAD microwave instrument operates at 60 and 183 GHz and measures temperature and water vapor, respectively, from 0- to 10-km altitude with a time resolution of 7 min. The radiometer has been successfully deployed at Dome C (Concordia Station), Antarctica ($75^{circ}06^{prime} hbox{S}$, $123^{circ}21^{prime} hbox{E}$, 3233 m amsl) during the first summertime campaign for 12 days in January–February 2009. The radiometer has been continuously running since January 2010, hosted within a dedicated shelter. We have used the very first set of HAMSTRAD data, recorded when the instrument was outdoors, to assess its potential to sound the troposphere over Dome C, from the planetary boundary layer (PBL) up to the tropopause ($sim$6 km above surface, $sim$9 km amsl). We have compared the HAMSTRAD measurements to several sets of measurements performed at the Dome-C station or in its vicinity: meteorological radiosondes, in situ PT100 and Humicap sondes along the vertical extent of a 45-m tower, meteorological sensor attached to the HAMSTRAD instrument, and the spaceborne Infrared Atmospheric Sounding Interferometer (IASI) instrument onboard the EUMETSAT MetOp-A satellite in polar orbit. The variability of integrated water vapor (IWV) observed by HAMSTRAD with extremely low values of 0.5 $hbox{kg} cdot hbox{m}^{-2}$ was also measured by the radiosondes (very high HAMSTRAD versus radiosonde correlation of 0.98), whereas IASI cloud-free measurements did not reproduce well the HAMSTRAD IWV variation (weak HAMSTRAD versus IASI correlation of 0.58). The measurements of absolute humidity $(hbox{H}{2}hbox{O})$ from HAMSTRAD at Dome C cover a large vertical extent from the surface to about 6 km above surface with a high sensitivity in the free troposphere. The strong diurnal v- riation of $hbox{H}{2}hbox{O}$ observed by the in situ sensors in the PBL is not well detected by the radiometer. In the free troposphere, the HAMSTRAD versus radiosonde $hbox{H}_{2}hbox{O}$ correlation can reach 0.8–0.9. Around the tropopause, HAMSTRAD shows the same variability as IASI and radiosondes but with a dry bias of 0.01 $hbox{g} cdot hbox{m}^{-3}$. HAMSTRAD tends to show a wetter atmosphere by 0.1–0.3 $hbox{g} cdot hbox{m}^{-3}$ compared with radiosondes from the surface to $sim$2-km altitude and a drier atmosphere above by $sim!! hbox{0.1} hbox{g} cdot hbox{m}^{-3}$. The sensitivity of the temperature profiles from HAMSTRAD is very high in the PBL and in the free troposphere but degrades around the tropopause. The strong diurnal signal measured above the surface by HAMSTRAD (3–6 K) is consistent with all the other in situ data sets. The temporal evolution over the 12-day period in the PBL is also consistent with all other data sets (radiosondes, IASI, in situ sondes, and meteorological sensors). In the free troposphere and around the tropopause, the HAMSTRAD temporal evolution is consistent with that observed by radiosondes and IASI, although a cold bias exists compared with IASI and radiosondes around the tropopause. For heights less than 4 km above surface, HAMSTRAD correlates very well with radiosondes and in situ sensors (correlation better than 0.8) but less well with IASI (0.4). Below the tropopause, the IASI and HAMSTRAD correlation reaches 0.9, whereas above the tropopause, the correlation of IASI and radiosondes with HAMSTRAD is rather low ($<$ 0.5). Throughout the 12-day period (except on January 23), in the lowermost troposphere for heights less than 500 m above surface, the HAMSTR
Keywords: Extraterrestrial measurements, Instruments, Microwave radiometry, Ocean temperature, Temperature measurement, Terrestrial atmosphere, Water, Antarctica, atmospheric measurements, humidity measurements, least squares methods, microwave measurements, microwave radiometry, temperature measurements, time series analysis,
Programme: 910,1013
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David Costantini, Pierre Blévin, Jan Ove Bustnes, Valérie Esteve, Geir Wing Gabrielsen, Dorte Herzke, Ségolène Humann-Guilleminot, Børge Moe, Charline Parenteau, Charlotte Récapet, Paco Bustamante, Olivier Chastel. (2022). Integument carotenoid-based colouration reflects contamination to perfluoroalkyl substances, but not mercury, in arctic black-legged kittiwakes (Vol. 10).
Abstract: Anthropogenic activities are introducing multiple chemical contaminants into ecosystems that act as stressors for wildlife. Perfluoroalkyl substances (PFAS) and mercury (Hg) are two relevant contaminants that may cause detrimental effects on the fitness of many aquatic organisms. However, there is a lack of information on their impact on the expression of secondary sexual signals that animals use for mate choice. We have explored the correlations between integument carotenoid-based colourations, blood levels of carotenoids, and blood levels of seven PFAS and of total Hg (THg) in 50 adult male black-legged kittiwakes (Rissa tridactyla) from the Norwegian Arctic during the pre-laying period, while controlling for other colouration influencing variables such as testosterone and body condition. Kittiwakes with elevated blood concentrations of PFAS (PFOSlin, PFNA, PFDcA, PFUnA, or PFDoA) had less chromatic but brighter bills, and brighter gape and tongue; PFOSlin was the pollutant with the strongest association with bill colourations. Conversely, plasma testosterone was the only significant correlate of hue and chroma of both gape and tongue, and of hue of the bill. Kittiwakes with higher concentrations of any PFAS, but not of THg, tended to have significantly higher plasma concentrations of the carotenoids astaxanthin, zeaxanthin, lutein, and cryptoxanthin. Our work provides the first correlative evidence that PFAS exposure might interfere with the carotenoid metabolism and the expression of integument carotenoid-based colourations in a free-living bird species. This outcome may be a direct effect of PFAS exposure or be indirectly caused by components of diet that also correlate with elevated PFAS concentrations (e.g., proteins). It also suggests that there might be no additive effect of THg co-exposure with PFAS on the expression of colourations. These results call for further work on the possible interference of PFAS with the expression of colourations used in mate choice.
Programme: 330
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Kenyon, S. L.; Lawrence, J. S.; Ashley, M. C. B.; Storey, J. W. V.; Tokovinin, A.; Fossat, E. (2006). Atmospheric Scintillation at Dome C, Antarctica: Implications for Photometryand Astrometry. The Publications of the Astronomical Society of the Pacific, 118(944), 924–932.
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T. Fruth, J. Cabrera, Sz Csizmadia, C. Dreyer, P. Eigmüller, A. Erikson, P. Kabath, T. Pasternacki, H. Rauer, R. Titz-Weider, L. Abe, A. Agabi, I. Gonçalves, T. Guillot, D. Mékarnia, J.-P. Rivet, N. Crouzet, R. Chini, R. Lemke, M. Murphy. (2014). Transit Search from Antarctica and Chile—Comparison and Combination (Vol. 126).
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Sims, G., M. C. B. Ashley, X. Cui, J. R. Everett, L. Feng, X. Gong, S. Hengst, Z. Hu, C. Kulesa, J. S. Lawrence, D. M. Luong-Van, P. Ricaud, Z. Shang, J. W. V. Storey, L. Wang, H. Yang, J. Yang, X. Zhou, Z. Zhu. (2012). Precipitable Water Vapor above Dome A, Antarctica, Determined from Diffuse Optical Sky Spectra. Publications of the Astronomical Society of the Pacific, 124(911), 74–83.
Abstract: The high altitudes and extremely low temperatures of the Antarctic plateau result in an exceedingly low atmospheric water vapor content. In this article we estimate the precipitable water vapor at Dome A using optical spectra of the diffuse solar irradiance in the zenith direction. The spectra were obtained from the Nigel spectrometer at Dome A during 2009. We find that the Nigel spectra contain sufficient information to extract daily average water vapor estimates, which agree with satellite observations to within ± 0.22 mm . Finally, we use these water vapor estimates to model the optical and near-IR transmission (between 700 nm and 2.5 μm) of Dome A to demonstrate significant advantages gained in this wavelength range and compare it with that of Paranal and Chajnantor, two midlatitude observatories.
Programme: 910
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Krinner G. & Genthon C. (1998). GCM simulations of the Last Glacial Maximum surface climate of Greenland and Antarctica. Climate dynamics, 14(9), 741–758.
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Bondar T N, Golovkov V P, . (1992). IZMIRAN Candidate Models for DGRF 1985, IGRF 1990 and a Secular Variation Forecast Model for the 1990-1995 Period
. Journal of geomagnetism and geoelectricity, 44(9), 709–717.
Abstract: Two candidate main field models for 1985 and 1990 as well as a forecast for the secular variation are represented as a series of spherical harmonic coefficients up to n=m=10 and n=m=8, respectively. IZMSV, US/UK, USGS forecasting models are compared with extrapolated secular variation observations and with one another. The IZMSV and the USGS are shown to agree best.
Programme: 139
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