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Stephens, B.B.; Gurney, K.R.; Tans, P.P.; Sweeney, C.; Peters, W.; Bruhwiler, L.; Ciais, P.; Ramonet, M.; Bousquet, P.; Nakazawa, T.; Aoki, S.; Machida, T.; Inoue, G.; Vinnichenko, N.; Lloyd, J.; Jordan, A.; Heimann, M.; Shibistova, O.; Langenfelds, R.L.; Steele, L.P.; Francey, R.J.; Denning, A.S. (2007). Weak Northern and Strong Tropical Land Carbon Uptake from Vertical Profiles of Atmospheric CO2. Science, 316(5832), 1732–1735.
Abstract: Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of -1.5 petagrams of carbon per year (Pg C year-1) and weaker tropical emission of +0.1 Pg C year-1 compared with previous consensus estimates of -2.4 and +1.8 Pg C year-1, respectively. This suggests that northern terrestrial uptake of industrial CO2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO2.
Programme: 416
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Morin, S.; Savarino, J.; Frey, M.M.; Yan, N.; Bekki, S.; Bottenheim, J.W.; Martins, J.M.F. (2008). Tracing the Origin and Fate of NOx in the Arctic Atmosphere Using Stable Isotopes in Nitrate. Science, 322(5902), 730–732.
Abstract: Atmospheric nitrogen oxides (NOx =NO+ NO2) play a pivotal role in the cycling of reactive nitrogen (ultimately deposited as nitrate) and the oxidative capacity of the atmosphere. Combined measurements of nitrogen and oxygen stable isotope ratios of nitrate collected in the Arctic atmosphere were used to infer the origin and fate of NOx and nitrate on a seasonal basis. In spring, photochemically driven emissions of reactive nitrogen from the snowpack into the atmosphere make local oxidation of NOx by bromine oxide the major contributor to the nitrate budget. The comprehensive isotopic composition of nitrate provides strong constraints on the relative importance of the key atmospheric oxidants in the present atmosphere, with the potential for extension into the past using ice cores.
Programme: 1011
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Steffensen, J.P.; Andersen, K.K.; Bigler, M.; Clausen, H.B.; Dahl-Jensen, D.; Fischer, H.; Goto-Azuma, K.; Hansson, M.; Johnsen, S.J.; Jouzel, J.; Masson-Delmotte, V.; Popp, T.; Rasmussen, S.O.; Rothlisberger, R.; Ruth, U.; Stauffer, B.; Siggaard-Andersen, M.-L.; Sveinbjornsdottir, A.E.; Svensson, A.; White, J.W.C. (2008). High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years. Science, 321(5889), 680–684.
Abstract: The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.
Programme: 458
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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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Trampert, J.; Snieder, R. (1996). Model Estimations Biased by Truncated Expansions: Possible Artifacts in Seismic Tomography. Science, 271(5253), 1257–1260.
Abstract: In most linear imaging problems, where the model to be sought is expanded in a set of basis functions, it is common practice to truncate the set at a certain (arbitrary) level. The solution then depends on the chosen parameterization, and neglected basis functions may leak into the solution to produce artifacts in the retrieved model. An unbiased estimate of the coefficients of the true model may be obtained in the chosen finite basis set ; here, a method to suppress leakage is illustrated on an example of global seismic tomography.
Keywords: seismology ; tomography ; errors ; mathematical models ; methods ; inverse problem ; elastic waves ; Rayleigh waves ; algorithms
Programme: 133
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C. Tape, Q. Liu, A. Maggi, J. Tromp. (2009). Adjoint tomography of the southern California crust. Science, 325, 988–992.
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Wang Z, Chappellaz J, Park K, Mak J E, . (2010). Large Variations in Southern Hemisphere Biomass Burning During the Last 650 Years.
. Science, 330(6011), 1663–1666.
Abstract: We present a 650-year Antarctic ice core record of concentration and isotopic ratios ((13)C and (18)O) of atmospheric carbon monoxide. Concentrations decreased by ~25% (14 ppbv) from mid-1300s to the 1600s, then recovered completely by the late 1800s. (13)C and (18)O decreased by about 2 and 4 respectively from mid-1300s to the 1600s, then increase by about 2.5 and 4 by the late 1800s. These observations and isotope mass balance model results imply that large variations in the degree of biomass burning in the Southern Hemisphere occurred during the last 650 years, with a decrease by about 50% in the 1600s, an increase of about 100% by the late 1800s, and another decrease by about 70% from the late 1800s to present day.
Programme: 458
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. (2009). Ecological Dynamics Across the Arctic Associated with Recent Climate Change
. Science, 325(5946), 1355–1358.
Abstract: At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These rapid changes may be a bellwether of changes to come at lower latitudes and have the potential to affect ecosystem services related to natural resources, food production, climate regulation, and cultural integrity. We highlight areas of ecological research that deserve priority as the Arctic continues to warm.
Programme: 1036
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Weimerskirch Henri, Louzao Maite, de Grissac Sophie, Delord Karine, . (2012). Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits
. Science, 335 (6065 ), 211–214 .
Abstract: Westerly winds in the Southern Ocean have increased in intensity and moved poleward. Using long-term demographic and foraging records, we show that foraging range in wandering albatrosses has shifted poleward in conjunction with these changes in wind pattern, while their rates of travel and flight speeds have increased. Consequently, the duration of foraging trips has decreased, breeding success has improved, and birds have increased in mass by more than 1 kilogram. These positive consequences of climate change may be temporary if patterns of wind in the southern westerlies follow predicted climate change scenarios. This study stresses the importance of foraging performance as the key link between environmental changes and population processes.
Programme: 109
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Pinglot J.F. & Pourchet M. (1995). Radioactivity measurements applied to glaciers and lake sediments. Sci. Total Environ., 173/174, 211–223.
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