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. (2006). Current plate movements across the Mid-Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland. J. Geophys. Res., 111.
Keywords: Iceland crustal deformation; continuous GPS; 1240 Geodesy and Gravity: Satellite geodesy: results; 8150 Tectonophysics: Plate boundary: general; 1242 Geodesy and Gravity: Seismic cycle related deformations; 8158 Tectonophysics: Plate motions: present and recent; 7245 Seismology: Mid-ocean ridges
Programme: 316
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. (2012). (Vol. 117).
Keywords: stratosphere to troposphere exchange tropospheric ozone
Programme: 109
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. (2012). Observation of low shear wave velocity at the base of the polar ice sheets: evidence for enhanced anisotropy
. Geophysical Journal International , 190 (1 ), 391–405 .
Abstract: We analyse seismic data from the broad-band stations located on the Antarctic and Greenland ice sheets to determine the large-scale seismic parameters of the polar ice sheets. The P-to-S converted waves at the ice/rock interface and inside the ice sheets and their multiples (the P receiver functions) are used to estimate the in situ P velocity Vp and the P-to-S velocity ratio Vp/Vs of the polar ice. The thickness of the whole ice layer is precisely known either from radio echo soundings or from ice core drillings allowing thus an accurate determination of Vp and Vp/Vs. At some places in and near the Wilkes Basin, a sedimentary layer is probably squeezed between the ice and the bedrock. We find that the polar ice caps have a two-layer structure, the upper layer of variable thickness about 2/3 of the total thickness with velocities very close to the ice standard values and the lower layer preserving a standard Vp but with about 25 per cent smaller shear wave velocity and a more or less constant thickness. The shear-velocity drop in the lower layer may be the evidence of a strong anisotropy induced by preferred orientation of ice crystals and by fine layering of soft and hard ice layers. A large variation of ice viscosity with depth is therefore expected and heterogeneous flowing of the polar ice sheet. This heterogeneous flowing may invalidate the use at great depth of the ice dating models based on monotonic layer thinning.
Programme: 906
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. (2022). (Vol. 231).
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. (2021). Antarctic surface temperature and elevation during the Last Glacial Maximum (Vol. 372).
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Casado, M. A. Landais, V. Masson-Delmotte, C. Genthon, E. Kerstel, S. Kassi, L. Arnaud, G. Picard, F. Prie, O. Cattani, H.-C. Steen-Larsen, E. Vignon, and P. Cermak. (2016). Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau (Vol. 16). Bachelor's thesis, , .
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Masson-Delmotte, V.; Landais, A.; Stievenard, M.; Cattani, O.; Falourd, S.; Jouzel, J.; Johnsen, S.J.; Dahl-Jensen, D.; Sveinsbjornsdottir, A.; White, J.W.C.; Popp, T.; Fischer, H. (2005). Holocene climatic changes in Greenland: Different deuterium excess signals at Greenland Ice Core Project (GRIP) and NorthGRIP. J. Geophys. Res., 110.
Abstract: Water stable isotope measurements (?D and ?18O) have been conducted on the Holocene part of two deep Greenland ice cores (Greenland Ice Core Project (GRIP) and NorthGRIP), located ?320 km apart. These combined measurements provide the first two continuous Greenland Holocene deuterium excess profiles (d = ?D ? 8?18O), a parameter strongly influenced by changes in moisture sources. We discuss here temporal and regional fluctuations of the deuterium excess within central to north Greenland, with a mean temporal resolution of ?4 years. Although GRIP and NorthGRIP exhibit similar annual mean surface temperatures and ?18O levels, a significant offset of modern deuterium excess is observed between the two sites. We attribute this offset to a different mix of modern moisture sources, pointing to regional-scale differences in moisture advection toward Greenland. The common long-term deuterium excess Holocene increasing trend is probably related to the increased relative contribution of low-latitude moisture to Greenland snowfall, in response to the change in the Earth obliquity, as symmetrically observed in Antarctica. Three abrupt declines punctuate the GRIP excess record (8.2, 4.5, and 0.35 ka BP), suggesting associated reorganizations of the northern high latitudes hydrological cycle. The 8.2 ka BP event is characterized by (1) a rapid cooling followed by a progressive warming and (2) a deuterium excess cooling restricted to GRIP, therefore totally different from rapid events during glacial times. By contrast, the NorthGRIP deuterium excess record is more stable. We propose that a slightly larger proportion of moisture supplied by local storm tracks to GRIP induces an isotopic compensation mechanism between simultaneous site and source temperature coolings, resulting in a rather temperature-insensitive ?18O profile, together with well-marked deuterium excess amplitudes. NorthGRIP ?18O seems less biased by isotopic processes and should provide a more reliable past temperature record.
Keywords: paleoclimate; polar ice sheet; water cycle; 1041 Geochemistry: Stable isotope geochemistry; 0724 Cryosphere: Ice cores; 1620 Global Change: Climate dynamics; 1655 Global Change: Water cycles; 3344 Atmospheric Processes: Paleoclimatology
Programme: 458
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Capron E, Landais A, Lemieux-Dudon B, Schilt A, Masson-Delmotte V, Buiron D, Chappellaz J, Dahl-Jensen D, Johnsen S, Leuenberger M, Loulergue L, Oerter H, . (2010). Synchronising EDML and NorthGRIP ice cores using δ18O of atmospheric oxygen (δ18Oatm) and CH4 measurements over MIS5 (80-123 kyr)
. Quat Sci Rev, 29(1-2), 222–234.
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. (2021). Water Isotopic Signature of Surface Snow Metamorphism in Antarctica (Vol. 48).
Abstract: Water isotope ratios of ice cores are a key source of information on past temperatures. Through fractionation within the hydrological cycle, temperature is imprinted in the water isotopic composition of snowfalls. However, this signal of climatic interest is modified after deposition when snow remains at the surface exposed to the atmosphere. Comparing time series of surface snow isotopic composition at Dome C with satellite observations of surface snow metamorphism, we found that long summer periods without precipitation favor surface snow metamorphism altering the surface snow isotopic composition. Using excess parameters (combining D,17O, and 18O fractions) allow the identification of this alteration caused by sublimation and condensation of surface hoar. The combined measurement of all three isotopic compositions could help identifying ice core sections influenced by snow metamorphism in sites with very low snow accumulation.
Keywords: excess Ice cores metamorhism Paleoclimate water isotopes
Programme: 1110
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Mardon J, Nesterova A P, Traugott J, Saunders S M, Bonadonna F, . (2010). Insight of scent: experimental evidence of olfactory capabilities in the wandering albatross (Diomedea exulans)
. J. Exp. Biol., 213(4), 558–563.
Abstract: Wandering albatrosses routinely forage over thousands of kilometres of open ocean, but the sensory mechanisms used in the food search itself have not been completely elucidated. Recent telemetry studies show that some spatial behaviours of the species are consistent with the multimodal foraging strategy hypothesis which proposes that birds use a combination of olfactory and visual cues while foraging at sea. The multimodal foraging strategy hypothesis, however, still suffers from a lack of experimental evidence, particularly regarding the olfactory capabilities of wandering albatrosses. As an initial step to test the hypothesis, we carried out behavioural experiments exploring the sensory capabilities of adult wandering albatrosses at a breeding colony. Three two-choice tests were designed to investigate the birds' response to olfactory and visual stimuli, individually or in combination. Perception of the different stimuli was assessed by comparing the amount of exploration directed towards an experimental display or a control display. Our results indicate that birds were able to perceive the three types of stimulus presented: olfactory, visual and combined. Moreover, olfactory and visual cues were found to have additional effects on the exploratory behaviours of males. This simple experimental demonstration of reasonable olfactory capabilities in the wandering albatross supports the multimodal foraging strategy and is consistent with recent hypotheses of the evolutionary history of procellariiforms.
Programme: 354
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