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Karlöf, L.; Winther, J.-G.; Isaksson, E.; Kohler, J.; Pinglot, J.F.; Wilhelms, F.; Hansson, M.; Holmlund, P.; Nyman, M.; Pettersson, R.; Stenberg, M.; Thomassen, M.P.A.; van der Veen, C.; van de Wal, R.S.W. (1999). A 1500 year record of accumulation at Amundsenisen western Dronning Maud Land, Antarctica, derived from electrical and radioactive measurements on a 120 m ice core. J. Geophys. Res., 105.
Abstract: During the Nordic EPICA pre-site survey in Dronning Maud Land in 1997/1998 a 120 m long ice core was retrieved (76°00'S 08°03'W, 2400 m above sea level). The whole core has been measured using the electric conductivity measurement (ECM) and dielectric profiling (DEP) techniques, and the core chronology has been established by detecting major volcanic eruptions. In a nearby shallow core radioactive traces from nuclear tests conducted during the 1950s and 1960s have been identified. Altogether, 13 ECM and DEP peaks in the long core are identified as originating from specific volcanic eruptions. In addition two peaks of increased total ? activity are identified in the short core. Accumulation is calculated as averages over the time periods between these dated events. Accumulation rate is 62 millimetres (w. eq./yr) for the last 181 years (1816 A.D. to present) and 61 mm w. eq./yr for the last 1457 years (540 A.D. to present). Our record shows an 8% decrease in accumulation between 1452 and 1641 A.D. (i.e. part of the Little Ice Age), compared to the long-term mean.
Programme: 265
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Geirsson, H.; Árnadóttir, T.; Völksen, C.; Jiang, W.; Sturkell, E.; Villemin, T.; Einarsson, P.; Sigmundsson, F.; Stefánsson, R. (2006). Current plate movements across the Mid-Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland. J. Geophys. Res., 111.
Abstract: We analyze data spanning up to 5 years from 18 continuous GPS stations in Iceland, computing daily positions of the stations with three different high-level geodetic processing software packages. We observe large-scale crustal deformation due to plate spreading across Iceland. The observed plate divergence between the North American and the Eurasian plates is in general agreement with existing models of plate motion. Spreading is taken up within a ?100–150 km wide plate boundary zone that runs through the island. Of the two parallel branches of the plate boundary in south Iceland, the eastern volcanic zone is currently taking up the majority of the spreading and little is left for the western volcanic zone. The plate boundary deformation field has been locally and temporarily affected in south Iceland by two M w = 6.5 earthquakes in June 2000, inflation at Katla volcano during 2000 to 2004, and an eruption of Hekla volcano in February 2000. All stations with significant vertical velocities are moving up relative to the reference station REYK, with the highest velocity exceeding 20 mm/yr in the center of the island.
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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Criscuolo, F.; Bertile, F.; Durant, J. M.; Raclot, T.; Gabrielsen, G. W.; Massemin, S.; Chastel, O. (2006). Body Mass and Clutch Size May Modulate Prolactin and Corticosterone Levels in Eiders. Physiol. Biochem. Zool., 79(3), 514–521.
Abstract: Altered body condition, increased incubation costs, and egg loss are important proximate factors modulating bird parental behavior, since they inform the adult about its remaining chances of survival or about the expected current reproductive success. Hormonal changes should reflect internal or external stimuli, since corticosterone levels (inducing nest abandonment) are known to increase while body condition deteriorates, and prolactin levels (stimulating incubation) decrease following egg predation. However, in a capital incubator that based its investment on available body reserves and naturally lost about half of its body mass during incubation, corticosterone should be maintained at a low threshold to avoid protein mobilization for energy supply. This study focused on the regulation of corticosterone and prolactin release in such birds during incubation, when facing egg manipulation (control, reduced, or increased) or a stressful event. Blood samples were taken before and after clutch manipulation and at hatching. Corticosterone levels were determined before and after 30 min of captivity. Female eiders exhibited a high hypothalamic?pituitary?adrenal sensitivity, plasma concentration of corticosterone being increased by four? to fivefold following 30 min of captivity. The adrenocortical response was not modified by body mass loss but was higher in birds for which clutch size was increased. In the same way, females did not show different prolactin levels among the experimental groups. However, when incubation started, prolactin levels were correlated to body mass, suggesting that nest attendance is programmed in relation to the female initial body condition. Moreover, due to an artifactual impact of bird manipulation, increased baseline corticosterone was associated with a prolactin decrease in the control group. These data suggest that, in eiders, body mass and clutch size modification can modulate prolactin and corticosterone levels, which cross?regulate each other in order to finely control incubation behavior.
Programme: 332
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Van Petegem, F.,; Collins, T.,; Meuwis, M.-A.,; Gerday, C.,; Feller, G.,; Van Beeumen, J.,. (2002). Crystallization and preliminary X-ray analysis of a xylanase from the psychrophile Pseudoalteromonas haloplanktis. Acta Crystallogr. D Biol. Crystallogr., 58(9), 1494–1496.
Abstract: The 46 kDa xylanase from the Antarctic microorganism Pseudoalteromonas haloplanktis is an enzyme that efficiently catalyzes reactions at low temperatures. Here, the crystallization of both the native protein and the SeMet-substituted enzyme and data collection from both crystals using synchrotron radiation are described. The native data showed that the crystals diffract to 1.3 A resolution and belong to space group P212121, with unit-cell parameters a = 50.87, b = 90.51, c = 97.23 A. SAD data collected at the peak of the selenium absorption edge proved to be sufficient to determine the heavy-atom configuration and to obtain electron density of good quality.
Keywords: psychrophiles; cold-adapted enzyme; glycosyl hydrolases
Programme: 193
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Le Quere, C.; Rodenbeck, C.; Buitenhuis, E.T.; Conway, T.J.; Langenfelds, R.; Gomez, A.; Labuschagne, C.; Ramonet, M.; Nakazawa, T.; Metzl, N.; Gillett, N.; Heimann, M. (2007). Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change. Bachelor's thesis, , .
Abstract: Based on observed atmospheric CO2 concentration and an inverse method, we estimate that the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 PgC/y per decade relative to the trend expected from the large increase in atmospheric CO2. This weakening is attributed to the observed increase in Southern Ocean winds resulting from human activities and projected to continue in the future. Consequences include a reduction in the efficiency of the Southern Ocean sink of CO2 in the short term (~25 years) and possibly a higher level of stabilization of atmospheric CO2 on a multicentury time scale.
Programme: 416;439
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Fain, X.; Ferrari, C.P.; Gauchard, P.-A.; Magand, O.; Boutron, C. (2006). Fast depletion of gaseous elemental mercury in the Kongsvegen Glacier snowpack in Svalbard. Geophysical research letters, 33.
Abstract: Gaseous elemental mercury (GEM, Hg°) was measured in the snowpack interstitial air on the Kongsvegen Glacier (Svalbard) between the surface and 190 cm depth. A rapid depletion of GEM from ?5 to 0.4 ng.m?3 in the snowpack air was measured in less than 8 hours at a calculated depletion rate of ?0.5–0.7 ng.m?3.h?1 while concentration of GEM above the snow stayed constant about 1.7 ng.m?3. This depletion could only be explained by chemical processes and this study suggests that Br. could be the most important reactant for the oxidation of GEM in the interstitial snow air. The lifetime of GEM was estimated to be ?10 minutes with second order reaction rate constant between GEM and Br. of about ?2 × 10?11 cm?3.molecule?1.s?1. These first experimental kinetic values for GEM oxidation in the snow air are in good agreement with both theoretical and modelling studies previously reported.
Keywords: 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0330 Atmospheric Composition and Structure: Geochemical cycles; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0736 Cryosphere: Snow
Programme: 399
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Saether, B.-E.; Lande, R.; Engen, S.; Weimerskirch, H.; Lillegard, M.; Altwegg, R.; Becker, P.H.; Bregnballe, T.; Brommer, J.E.; McCleery, R.H.; Merila, J.; Nyholm, E.; Rendell, W.; Robertson, R.R.; Tryjanowski, P.; Visser, M.E. (2005). Generation time and temporal scaling of bird population dynamics. AADE editors' journal, 436(7047), 99–102.
Abstract: Theoretical studies have shown that variation in density regulation strongly influences population dynamics1, yet our understanding of factors influencing the strength of density dependence in natural populations still is limited2. Consequently, few general hypotheses have been advanced to explain the large differences between species in the magnitude of population fluctuations3, 4, 5, 6. One reason for this is that the detection of density regulation in population time series is complicated by time lags induced by the life history of species7, 8 that make it difficult to separate the relative contributions of intrinsic and extrinsic factors to the population dynamics. Here we use population time series for 23 bird species to estimate parameters of a stochastic density-dependent age-structured model. We show that both the strength of total density dependence in the life history and the magnitude of environmental stochasticity, including transient fluctuations in age structure, increase with generation time. These results indicate that the relationships between demographic and life-history traits in birds9, 10 translate into distinct population dynamical patterns that are apparent only on a scale of generations.
Programme: 109
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Andersen, O.B.; Hinderer, J. (2005). Global inter-annual gravity changes from GRACE: Early results. Geophysical research letters, 32.
Abstract: Fifteen monthly gravity field solutions from the GRACE twin satellites launched more than two years ago have been studied to estimate gravity field changes between 2002 and 2003.The results demonstrate that GRACE is capable of capturing the changes in ground water on inter-annual scales with an accuracy of 0.4 ?Gal corresponding to 9 mm water thickness on spatial scales longer than 1300 km. Four of the most widely used global hydrological models have been investigated for their spatial comparison with GRACE observations of inter-annual gravity field variations due to changes in continental water storage. The Global Land Data Assimilation System model has a spatial correlation coefficient with GRACE observations of 0.65 over the northern hemisphere. This demonstrates that the observed gravity field changes on these scales are largely related to changes in continental water storage.
Keywords: 1217 Geodesy and Gravity: Time variable gravity; 1855 Hydrology: Remote sensing; 1640 Global Change: Remote sensing; 1655 Global Change: Water cycles
Programme: 337
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Andersen, O.B.; Seneviratne, S.I.; Hinderer, J.; Viterbo, P. (2005). GRACE-derived terrestrial water storage depletion associated with the 2003 European heat wave. Geophysical research letters, 32.
Abstract: The GRACE twin satellites reveal large inter-annual terrestrial water-storage variations between 2002 and 2003 for central Europe. GRACE observes a negative trend in regional water storage from 2002 to 2003 peaking at ?7.8 cm in central Europe with an accuracy of 1 cm. The 2003 excess terrestrial water storage depletion observed from GRACE can be related to the record-breaking heat wave that occurred in central Europe in 2003. We validate the measurements from GRACE using two independent hydrological estimates and direct gravity observations from superconducting gravimeters in Europe. All datasets agree well with the GRACE measurements despite the disparity of the employed information; the difference between datasets tends to be within GRACE margin of error. The April-to-August terrestrial water storage depletion is found to be significantly larger in 2003 than in 2002 from both models and observations.
Keywords: 1640 Global Change: Remote sensing; 1655 Global Change: Water cycles; 1836 Hydrology: Hydrological cycles and budgets; 1812 Hydrology: Drought
Programme: 337
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Williams, J.; Gros, V.; Bonsang, B.; Kazan, V. (2001). HO cycle in 1997 and 1998 over the southern Indian Ocean derived from CO, radon, and hydrocarbon measurements made at Amsterdam Island. J. Geophys. Res., 106(d12), 12,719–12,725.
Abstract: A new empirical method for the derivation of average HO radical concentrations is presented. The method is based on estimation of CO lifetime through the relative variability of CO and Rn measurements, and hydrocarbon measurements are used to independently determine the relative effects of chemistry and dynamics. Data from Amsterdam Island (37°S, 77°E), a remote site in the southern Indian Ocean, are used to calculate annual and daily HO levels for 1997 and 1998. A seasonal variation in calculated daily HO, consistent with seasonally changing photolysis rates, with maxima in summer and minima in winter is also derived which is comparable but slightly lower than the most recent zonal mean HO estimates of Spivakovsky et al. [2000]. The calculated annual HO shows a decrease from 2.7 × 105 molecule cm?3 in 1997 to 0.8 × 105 molecule cm?3 in 1998, possibly as a result of El Niño related meteorological changes. The empirically calculated HO correlates with temperature and relative humidity measured at the island but anticorrelates strongly with CO and to a lesser extent with O3. The limitations and improvements to this method are discussed. The method has potential for long-term monitoring of HO changes over areas upwind from remote sites.
Programme: 415
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