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Memin A, Rogister Y, Hinderer J, Llubes M, Berthier E, Boy J-P, . (2009). Ground deformation and gravity variations modelled from present-day ice thinning in the vicinity of glaciers
. Journal of Geodynamics, 48(35), 195–203.
Abstract: The solid Earth deforms because of post-glacial rebound due to the viscous relaxation following the last deglaciation but also because of present-day elastic deformation induced by ice thinning. In this paper, we compute elastic loading Greens function associated to the tilt of the ground in the vicinity of glaciers using a Love number formalism for a stratified non-rotating spherical Earth model. We compare this global approach with the plane approximation in terms of height, gravity and tilt changes as a function of the distance from the measurement point to the load. We find that Greens functions for the vertical displacement (resp. horizontal displacement, elastic part of the tilt) agree to within 1% up to 400 m (resp. 2 km, 5 km) from the glaciers. Two specific cases of ice thinning are considered: (1) the alpine glaciers of the Mont Blanc region (France) where ice-thickness variations are derived from differential digital elevation model analysis for the period 19792003; (2) the Svalbard (Norway) glaciers by considering the ice model SVAL. We show that the rates of ground tilt are well above the limit of detection of up-to-date long-base hydrostatic tiltmeters, which, if installed next to the glaciers, could be used to monitor the time evolution of ice thinning. We also show that the topography has a strong influence on the gravity variations near the glaciers.
Keywords: Ground tilt, Gravity variations, Elastic deformations, Present-day ice thinning,
Programme: 337
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Bernard É, Friedt JM, Tolle F, Griselin M, Martin G, Laffly D, Marlin C, . (2013). Monitoring seasonal snow dynamics using ground based high resolution photography (Austre Lovénbreen, Svalbard, 79°N). ISPRS Journal of Photogrammetry and Remote Sensing, 75, 92–100.
Abstract: Arctic glaciers are reliable indicators of global climate changes. However, monitoring snow and ice dynamics in Arctic regions is challenging: some fast but key events can be missed since they are short in time but significant in the hydrological budget.
Keywords: Ground based camera, Snow cover dynamics, In situ sensing, Geometric correction, Digital camera, Svalbard, Glacier, High temporal resolution,
Programme: 304,1108,1111
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Germe Agathe, Houssais Marie-Nolle, Herbaut Christophe, Cassou Christophe, . (2011). Greenland Sea sea ice variability over 1979–2007 and its link to the surface atmosphere
. J. Geophys. Res., 116(C10), C10034–.
Abstract: Mean winter Arctic sea ice concentration based on passive microwave observations for the period 1979–2007 are analyzed to examine the variability of the western Nordic Seas marginal ice zone (MIZ). A principal component analysis performed on this regional domain shows that the interannual variability is dominated by a mode which captures more than 70% of the total variance and shows only moderate correlation with the leading mode of global Northern Hemisphere sea ice variability. This mode appears to be related to a pattern of sea level pressure (SLP) anomaly centered on the MIZ with large scale signature resembling the canonical pattern of the North Atlantic Oscillation (NAO). Still this leading mode of SIC variability shows a weak temporal correlation with the NAO index. Taking into account the intrinsic spatial asymmetry found between the two phases of the NAO based on a weather regimes analysis, composite SIC fields are constructed which indeed suggest a preferential response of the Greenland Sea SIC variability to negative NAO-like patterns of SLP. The SLP pattern is consistent with a response of the sea ice margin to the strength of the northerly winds along eastern Greenland. A weak pattern of surface air temperature anomalies also emerges in the central Greenland Sea which occurs, at least partly, as a response of the surface atmosphere to sea ice concentrations changes. Higher order modes of winter SIC variability emerge based on a shorter winter season. One mode has much resemblance with the Odden/Nordbukta pattern while another one exhibits a significant signature in the center of the Greenland Sea convective gyre. The Odden/Nordbukta mode shows a more symmetric relation to the NAO than the leading SIC mode. Linear regression analysis consistently suggests some link between this mode and the ice area flux through Fram Strait.
Keywords: Greenland Sea, sea ice, 0750 Cryosphere: Sea ice (4540), 3339 Atmospheric Processes: Ocean/atmosphere interactions (0312, 4301, 4504), 4215 Oceanography: General: Climate and interannual variability (1616, 1635, 3305, 3309, 4513),
Programme: 452
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Niels Martin Schmidt, Tomas Roslin, Lars Holst Hansen, Olivier Gilg, Johannes Lang, Benoit Sittler, Jannik Hansen, Loïc Bollache, Eero Vesterinen. (2022). Spatio-temporal patterns in arctic fox (Vulpes alopex) diets revealed by molecular analysis of scats from Northeast Greenland (Vol. 32).
Abstract: The arctic fox (Vulpes lagopus) is endemic to the Arctic where it holds a central position in the trophic interactions. The diet of the species has previously been described as being highly flexible, but whether this flexibility is a constant trait through time, or merely reflects fast temporal changes in abundance among prey taxa, has so far been poorly resolved. Using molecular analyses of arctic fox scats from Northeast Greenland, we first examined the temporal dynamics of arctic fox diets during the short snow-free season, and then examined whether local food availability at different sites affected arctic fox dependence on lemmings. Arctic fox diets included most terrestrial vertebrate species found in the region, and exhibited substantial temporal changes, generally reflecting the dynamic changes in prey availability from late winter through autumn. This dietary flexibility was also reflected geographically, with arctic foxes consuming a variety of local prey (mainly waterfowl and lemmings) in summer. Moreover, the dietary response of arctic foxes to changes in lemming abundance depended on access to non-lemming prey. Based on these findings, we discuss whether varying degrees of lemming-dependency, combined with geographical differences in winter food availability, may explain previously published differences in arctic fox breeding patterns in high arctic Greenland.
Keywords: Greenland Metabarcoding Predation Trophic interactions Tundra
Programme: 1036
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Benoît Sittler, Adrian Aebischer, Olivier Gilg. (2011). Post-breeding migration of four Long-tailed Skuas (Stercorarius longicaudus) from North and East Greenland to West Africa (Vol. 152).
Abstract: The Long-tailed Skua (Stercorarius longicaudus) is a specialist predator of lemmings during the summer and hence an important component of the tundra ecosystems, but most of its life cycle takes place offshore and remains largely unknown outside of the breeding season. Using 9.5-g solar-powered satellite transmitters, we were able to document for the first time the post-breeding movements of the Long-tailed Skua, from its high-Arctic breeding-grounds in North and Eastern Greenland to the tropical waters of West Africa. The birds traveled the approximately 10,000 km of this migration in only 3–5 weeks, covering 800–900 km/day during active migration, which also occurred during nighttime. Leaving their breeding areas in August (except for one failed breeder), the Long-tailed Skuas first moved south along the coast of East Greenland towards a staging area off the Canadian Great Banks where they stayed for 1–3 weeks. From there, they crossed the Atlantic Ocean eastwards in just 1 week, entering African waters near the Madeira Archipelago in September. Although only four birds were monitored for 1.5–3 months, the data reveal that the migration routes between birds breeding in different locations and in different years were relatively similar.
Keywords: Greenland Long-tailed Skua Post-breeding migration Rates of travel Satellite tracking Staging area Upwelling
Programme: 1036
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Fund F, Perosanz F, Testut L, Loyer S, . (2013). An Integer Precise Point Positioning technique for sea surface observations using a GPS buoy
. Adv Space Res, 51(8), 1311–1322.
Abstract: GPS data dedicated to sea surface observation are usually processed using differential techniques. Unfortunately, the precision of resulting kinematic positions is baseline-length dependent. So, high precision sea surface observations using differential GPS techniques are limited to coasts, lakes, and rivers. Recent improvements in GPS satellite products (orbits, clocks, and phase biases) make phase ambiguity fixing at the zero difference level achievable and opens up the observation of the sea surface without geographical constraints. This paper recalls the concept of the Integer Precise Point Positioning technique and discusses the precision of GPS buoy positioning. A sequential version of the GINS software has been implemented to achieve single epoch GPS positioning. We used 1 Hz data from a two week GPS campaign conducted in the Kerguelen Islands. A GPS buoy has been moored close to a radar gauge and 90 m away from a permanent GPS station. This infrastructure offers the opportunity to compare both kinematic Integer Precise Point Positioning and classical differential GPS positioning techniques to in situ radar gauge data. We found that Precise Point Positioning results are not significantly biased with respect to radar gauge data and that horizontal time series are consistent with differential processing at the sub-centimetre precision level. Nevertheless, standard deviations of height time series with respect to radar gauge data are typically [45] cm. The dominant driver for noise at this level is attributed to errors in tropospheric estimates which propagate into position solutions.
Keywords: GPS, Ambiguity fixing, Tropospheric delays, Buoy, Radar gauge,
Programme: 688
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Aymeric Fromant, Karine Delord, Charles-André Bost, Yonina H. Eizenberg, Jonathan A. Botha, Yves Cherel, Paco Bustamante, Brett R. Gardner, Maud Brault-Favrou, Arnaud Lec'hvien, John P. Y. Arnould. (2021). Impact of extreme environmental conditions: Foraging behaviour and trophic ecology responses of a diving seabird, the common diving petrel (Vol. 198).
Abstract: The reproductive success of birds is strongly driven by environmental conditions at different time scales. Thus, during periods of low food availability, breeding success is constrained by the ability of adults to adapt their foraging effort and feeding behaviour to maintain regular incubation shifts and chick provisioning. However, while large seabirds can buffer disruptions in prey availability, the ecophysiological constraints of smaller species may limit their behavioural flexibility. By combining information on at-sea movements, foraging habitat, trophic niche, and breeding success, this study evaluated the effects of intense variability in oceanographic conditions on common diving petrels (Pelecanoides urinatrix) at the northern extent of their range in south-eastern Australia during four consecutive breeding seasons. Unusually low breeding success (6 and 0%) was observed during two years with intense heatwave events, which were associated with higher foraging effort (foraging trips twice longer) and a substantial shift in trophic niche (lower blood δ15N values). These findings suggest that common diving petrels in Bass Strait may have reached a critical threshold above which buffering the effects of environmental variability on their reproductive output is not possible. The clear cascading impacts that marine heatwaves have on zooplankton feeders illustrate the profound bottom-up effect induced by such extreme environmental variations, and suggest strong impact on higher-trophic levels. The wide, circumpolar breeding distribution of the common diving petrel, and its high sensitivity to variations in oceanographic conditions, suggest that this species may be a suitable model to study short-term and long-term behavioural responses to the effects of climate change throughout the Southern Ocean.
Keywords: GPS tracking Habitat modelling Inter-annual variation Marine heatwave Stable isotopes
Programme: 109
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Meijer, Y.J.; Swart, D.P.J.; Allaart, M.; Andersen, S.B.; Bodeker, G.; Boyd, I.; Braathen, G.; Calisesi, Y.; Claude, H.; Dorokhov, V.; von der Gathen, P.; Gil, M.; Godin-Beekmann, S.; Goutail, F.; Hansen, G.; Karpetchko, A.; Keckhut, P.; Kelder, H.M.; Koelemeijer, R.; Kois, B.; Koopman, R.M.; Kopp, G.; Lambert, J.-C.; Leblanc, T.; McDermid, I.S.; Pal, S.; Schets, H.; Stubi, R.; Suortti, T.; Visconti, G.; Yela, M. (2004). Pole-to-pole validation of Envisat GOMOS ozone profiles using data from ground-based and balloon sonde measurements. J. Geophys. Res., 109.
Abstract: In March 2002 the European Space Agency (ESA) launched the polar-orbiting environmental satellite Envisat. One of its nine instruments is the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument, which is a medium-resolution stellar occultation spectrometer measuring vertical profiles of ozone. In the first year after launch a large group of scientists performed additional measurements and validation activities to assess the quality of Envisat observations. In this paper, we present validation results of GOMOS ozone profiles from comparisons to microwave radiometer, balloon ozonesonde, and lidar measurements worldwide. Thirty-one instruments/launch sites at twenty-five stations ranging from the Arctic to the Antarctic joined in this activity. We identified 6747 collocated observations that were performed within an 800-km radius and a maximum 20-hour time difference of a satellite observation, for the period between 1 July 2002 and 1 April 2003. The GOMOS data analyzed here have been generated with a prototype processor that corresponds to version 4.02 of the operational GOMOS processor. The GOMOS data initially contained many obviously unrealistic values, most of which were successfully removed by imposing data quality criteria. Analyzing the effect of these criteria indicated, among other things, that for some specific stars, only less than 10% of their occultations yield an acceptable profile. The total number of useful collocated observations was reduced to 2502 because of GOMOS data unavailability, the imposed data quality criteria, and lack of altitude overlap. These collocated profiles were compared, and the results were analyzed for possible dependencies on several geophysical (e.g., latitude) and GOMOS observational (e.g., star characteristics) parameters. We find that GOMOS data quality is strongly dependent on the illumination of the limb through which the star is observed. Data measured under bright limb conditions, and to a certain extent also in twilight limb, should be used with caution, as their usability is doubtful. In dark limb the GOMOS data agree very well with the correlative data, and between 14- and 64-km altitude their differences only show a small (2.5–7.5%) insignificant negative bias with a standard deviation of 11–16% (19–63 km). This conclusion was demonstrated to be independent of the star temperature and magnitude and the latitudinal region of the GOMOS observation, with the exception of a slightly larger bias in the polar regions at altitudes between 35 and 45 km.
Keywords: GOMOS; Envisat; ozone profile; validation; stratosphere; remote sensing; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0394 Atmospheric Composition and Structure: Instruments and techniques; 3360 Meteorology and Atmospheric Dynamics: Remote sensing; 3394 Meteorology and Atmospheric Dynamics: Instruments and techniques
Programme: 209
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Goutte Aurlie, Angelier Frdric, Welcker Jorg, Moe Brge, Clment-Chastel Cline, Gabrielsen Geir Wing, Bech Claus, Chastel Olivier, . (2010). Long-term survival effect of corticosterone manipulation in Black-legged kittiwakes
. Gen. Comp. Endocrinol., 167(2), 246–251.
Abstract: The secretion of corticosterone in response to stress is thought to be an adaptive mechanism, which promotes immediate survival at the expense of current reproduction. However, at the individual level, the hypothesis of a corticosterone-related survival appears to be complex. In this study, we tested this hypothesis by combining for the first time an experimental manipulation of corticosterone levels and capture-mark-recapture (CMR) models. To do so, we increased corticosterone levels of chick-rearing Black-legged kittiwakes (Rissa tridactyla) via subcutaneous implants. Then, we monitored the long-term survival of kittiwakes over the 2 consecutive years. Corticosterone-implanted birds showed a significantly lower apparent annual survival than sham-implanted ones (46.9% vs 77.8%). This result is supported by the well-known deleterious effects of elevated corticosterone levels on cognitive and immune functions. Alternately and in the light of recent studies, our experimental manipulation may have down-regulated the endogenous secretion of corticosterone through a prolonged negative feedback. If so, the corticosterone-implanted kittiwakes may have failed to trigger an appropriate stress response during subsequent life-threatening perturbations, hence being unable to adjust their behavior and physiology toward immediate survival. This study highlights the complex long-term consequences of corticosterone manipulation on fitness in free-living vertebrates.
Keywords: Glucocorticoids, Mortality, Long-lived seabirds, Rissa tridactyla,
Programme: 330
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Agnès Chounet, Martin Vallée. (2018). Global and Interregion Characterization of Subduction Interface Earthquakes Derived From Source Time Functions Properties (Vol. 123).
Abstract: Source time functions (STFs) describe how the seismic moment rate is released with time, and carry information on integral rupture properties, such as static stress drop and radiated energy. In this study, we systematically analyze a set of 1,433 STFs extracted from the SCARDEC method (Vallée and Douet, 2016, https://doi.org/10.1016/j.pepi.2016.05.012), containing the Mw≥5.6, shallow (z≤70 km) earthquakes with dip-slip mechanism that occurred between 1992 and 2014. At the global scale, STFs properties indicate scale invariance of stress drop and scaled radiated energy with magnitude. In a second step, these source parameters are investigated in light of the tectonic context of the earthquakes: in agreement with other approaches, we observe that subduction interface earthquakes have lower stress drop and scaled radiated energy relative to all other earthquakes (e.g., crustal earthquakes). Finally, a focus on subduction interface earthquakes (approximately 800 earthquakes) is done by considering 18 regional segments of subduction zones. We find that these segments do not have the same signature in terms of macroscopic rupture properties, which means that large-scale plate convergence and mechanical properties influence rupture behavior. In a given segment, local heterogeneities of stress drop or radiated energy can be associated with local features of the subduction zone: in particular, we find that low coupled zones generate earthquakes with low stress drop and scaled radiated energy. This last feature, also observed at a larger scale, suggests a positive correlation between coupling and stress drop.
Keywords: global earthquake seismology radiated energy seismic coupling source time functions stress drop subduction earthquakes
Programme: 133
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