A Comparison Of New Calculations Of The Yearly 10Be Production In The Earths Polar Atmosphere By Cosmic Rays With Yearly 10Be Measurements In Multiple Greenland Ice Cores Between 1939 And 1994 - A Troubling Lack Of Concordance Paper #2

We have compared the yearly production rates of 10Be by cosmic rays in the Earths polar atmosphere over the last 50-70 years with 10Be measurements from two separate ice cores in Greenland. These ice cores provide measurements of the annual 10Be concentration and 10Be flux levels during this time. The scatter in the ice core yearly data vs. the production data is larger than the average solar 11 year production variations that are being measured. The cross correlation coefficients between the yearly 10Be production and the ice core 10Be measurements for this time period are <0.4 in all comparisons between ice core data and 10Be production, including 10Be concentrations, 10Be fluxes and in comparing the two separate ice core measurements. In fact, the cross correlation between the two ice core measurements, which should be measuring the same source, is the lowest of all, only ~0.2. These values for the correlation coefficient are all indicative of a "poor" correlation. The regression line slopes for the best fit lines between the 10Be production and the 10Be measurements used in the cross correlation analysis are all in the range 0.4-0.6. This is a particular problem for historical projections of solar activity based on ice core measurements which assume a 1:1 correspondence. We have made other tests of the correspondence between the 10Be predictions and the ice core measurements which lead to the same conclusion, namely that other influences on the ice core measurements, as large as or larger than the production changes themselves, are occurring. These influences could be climatic or instrumentally based. We suggest new ice core measurements that might help in defining more clearly what these influences are and-if possible-to correct for them.Comment: 24 pages, 6 figure

Acquisition of isotopic composition for surface snow in East Antarctica and the links to climatic parameters

The isotopic compositions of oxygen and hydrogen in ice cores are invaluable tools for the reconstruction of past climate variations. Used alone, they give insights into the variations of the local temperature, whereas taken together they can provide information on the climatic conditions at the point of origin of the moisture. However, recent analyses of snow from shallow pits indicate that the climatic signal can become erased in very low accumulation regions, due to local processes of snow reworking. The signal-to-noise ratio decreases and the climatic signal can then only be retrieved using stacks of several snow pits. Obviously, the signal is not completely lost at this stage, otherwise it would be impossible to extract valuable climate information from ice cores as has been done, for instance, for the last glaciation. To better understand how the climatic signal is passed from the precipitation to the snow, we present here results from varied snow samples from East Antarctica. First, we look at the relationship between isotopes and temperature from a geographical point of view, using results from three traverses across Antarctica, to see how the relationship is built up through the distillation process. We also take advantage of these measures to see how second-order parameters (d-excess and O-17-excess) are related to delta O-18 and how they are controlled. d-excess increases in the interior of the continent (i.e., when delta O-18 decreases), due to the distillation process, whereas O-17-excess decreases in remote areas, due to kinetic fractionation at low temperature. In both cases, these changes are associated with the loss of original information regarding the source. Then, we look at the same relationships in precipitation samples collected over 1 year at Dome C and Vostok, as well as in surface snow at Dome C. We note that the slope of the delta O-18 vs. temperature (T) relationship decreases in these samples compared to those from the traverses, and thus caution is advocated when using spatial slopes for past climate reconstruction. The second-order parameters behave in the same way in the precipitation as in the surface snow from traverses, indicating that similar processes are active and that their interpretation in terms of source climatic parameters is strongly complicated by local temperature effects in East Antarctica. Finally we check if the same relationships between delta O-18 and second-order parameters are also found in the snow from four snow pits. While the d-excess remains opposed to delta O-18 in most snow pits, the O-17-excess is no longer positively correlated to delta O-18 and even shows anti-correlation to delta O-18 at Vostok. This may be due to a stratospheric influence at this site and/or to post-deposition processes

Clôture de la quatrième Année polaire internationale

Symposium organisé conjointement par le Collège de France et l’Office parlementaire d’évaluation des choix scientifiques et technologiques, Sénat et Assemblée nationale (OPECST). 14-15 mai 2009

End of the fourth International Polar Year

The fourth International Polar Year (IPY) officially came to an end on 14 and 15 May 2009 with a symposium organized jointly by the Collège de France and OPECST (the French parliamentary committee for the evaluation of scientific and technological choices). Many scientists and political actors, invited by Professor Édouard Bard and Senator Christian Gaudin, emphasized the success of the IPY, including the creation of at least 200 international multidisciplinary research projects, entirely dev..

Etude des anomalies isotopiques du soufre et de l'oxygène dans le sulfate d'origine volcanique enregistré dans les archives glaciaires

Le volcanisme plinien modifie le climat pendant plusieurs années en injectant de grandes quantités de dioxyde de soufre directement dans la stratosphère, oxydé ensuite en gouttelettes d'acide sulfurique qui réfléchissent les rayonnements solaires et changent les propriétés radiatives de l'atmosphère. L'étude de signaux volcaniques préservés dans les archives glaciaires, consistait jusqu'à présent à simplement mesurer les concentrations de sulfate. Nous proposons l'utilisation de nouveaux traceurs que sont les anomalies isotopiques de l'oxygène et du soufre de sulfate volcanique enregistré à Dôme C et Pôle Sud pour apporter de nouvelles informations sur le volcanisme passé. Une étude de l'évolution temporelle des anomalies isotopiques de l'oxygène et du soufre dans les sulfates volcaniques de l'Agung (mars 1963) et du Pinatubo (juin 1991) a été menée. L'anomalie isotopique du soufre change de signe au cours du temps et passe d'une phase positive, au début du dépôt de sulfate à une phase négative à la fin. Ce changement de signe s'accompagne d'un appauvrissement en isotopes lourds avec le temps. L'anomalie isotopique du soufre est créée à partir d'une réaction d'oxydation photochimique de SO2 en acide sulfurique, suggérant un processus rapide qui dure un mois environ. L'anomalie isotopique de l'oxygène, quant à elle, a permis d'établir un lien avec l'oscillation quasi-biennale de la stratosphère. Douze signaux volcaniques ont été étudiés dans leur globalité au cours du dernier millénaire. L'anomalie isotopique du soufre a permis d'identifier 6 éruptions volcaniques stratosphériques révélant l'utilité d'un tel traceur lorsque la nature des éruptions est méconnue.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Persistent Draining of the Stratospheric 10 Be Reservoir After the Samalas Volcanic Eruption (1257 CE)

International audienceMore than 2,000 analyses of beryllium-10 (Be-10) and sulfate concentrations were performed at a nominal subannual resolution on an ice core covering the last millennium as well as on records from three sites in Antarctica (Dome C, South Pole, and Vostok) to better understand the increase in Be-10 deposition during stratospheric volcanic eruptions. A significant increase in Be-10 concentration is observed in 14 of the 26 volcanic events studied. The slope and intercept of the linear regression between Be-10 and sulfate concentrations provide different and complementary information. Slope is an indicator of the efficiency of the draining of Be-10 atoms by volcanic aerosols depending on the amount of SO2 released and the altitude it reaches in the stratosphere. Intercept gives an image of the Be-10 production in the stratospheric reservoir, ultimately depending on solar modulation. The Samalas event (1257 CE) stands out from the others as the biggest eruption of the last millennium with the lowest positive slope of all the events. We hypothetize that the persistence of volcanic aerosols in the stratosphere after the Samalas eruption has drained the stratospheric Be-10 reservoir for a decade, meaning that solar reconstructions based on Be-10 should be considered with caution during this period. The slope of the linear regression between Be-10 and sulfate concentrations can also be used to correct the Be-10 snow/ice signal of the volcanic disturbance

Mass-Independent Sulfur Isotopic Compositions in Stratospheric Volcanic Eruptions

International audienceThe observed mass-independent sulfur isotopic composition (33S) of volcanic sulfate from the Agung (March 1963) and Pinatubo (June 1991) eruptions recorded in the Antarctic snow provides a mechanism for documenting stratospheric events. The sign of 33S changes over time from an initial positive component to a negative value. 33S is created during photochemical oxidation of sulfur dioxide to sulfuric acid on a monthly time scale, which indicates a fast process. The reproducibility of the results reveals that 33S is a reliable tracer to chemically identify atmospheric processes involved during stratospheric volcanism

The NO+O3 reaction: A triple oxygen isotope perspective on the reaction dynamics and atmospheric implications for the transfer of the ozone isotope anomaly

International audienceAtmospheric nitrate shows a large oxygen isotope anomaly (Δ 17O), characterized by an excess enrichment of 17O over 18O, similar to the ozone molecule. Modeling and observations assign this specific isotopic composition mainly to the photochemical steady state that exists in the atmosphere between ozone and nitrate precursors, namely, the nitrogen oxides (NOx=NO+NO2). However, this transfer is poorly quantified and is built on unverified assumptions about which oxygen atoms of ozone are transferred to NOx, greatly weakening any interpretation of the nitrate oxygen isotopic composition in terms of chemical reaction pathways and the oxidation state of the atmosphere. With the aim to improve our understanding and quantify how nitrate inherits this unusual isotopic composition, we have carried out a triple isotope study of the reaction NO+O3. Using ozone intramolecular isotope distributions available in the literature, we have found that the central atom of the ozone is abstracted by NO with a probability of (8+/-5)%(+/-2σ) at room temperature. This result is at least qualitatively supported by dynamical reaction experiments, the non-Arrhenius behavior of the kinetic rate of this reaction, and the kinetic isotope fractionation factor. Finally, we have established the transfer function of the isotope anomaly of O3 to NO2, which is described by the linear relationship Δ 17O(NO2)=A×Δ 17O(O3)+B, with A=1.18+/-0.07(+/-1σ) and B=(6.6+/-1.5)‰(+/-1σ). Such a relationship can be easily incorporated into models dealing with the propagation of the ozone isotope anomaly among oxygen-bearing species in the atmosphere and should help to better interpret the oxygen isotope anomaly of atmospheric nitrate in terms of its formation reaction pathways

Holocene dust in East Antarctica: provenance and variability in time and space

In this paper, we provide a comprehensive overview of the state-of-knowledge of dust flux and variability in time and space in different sectors of East Antarctica during the Holocene. By integrating the literature data with new evidences, we discuss the dust flux and grain-size variability during the current interglacial and its provenance in the innermost part of the East Antarctic plateau as well as in peripheral regions located close to the Transantarctic Mountains. The local importance of aeolian mineral dust aerosol deflated from low-elevation areas of peripheral East Antarctica is also discussed in the light of new data from several coastal, low-elevation sites

Cold decade (AD 1810–1819) caused by Tambora (1815) and another (1809) stratospheric volcanic eruption

International audienceClimate records indicate that the decade of AD 1810–1819 including “the year without a summer” (1816) is probably the coldest during the past 500 years or longer, and the cause of the climatic extreme has been attributed primarily to the 1815 cataclysmic Tambora eruption in Indonesia. But the cold temperatures in the early part of the decade and the timing of the Tambora eruption call into question the real climatic impact of volcanic eruptions. Here we present new evidence, based on sulfur isotope anomaly (Δ33S), a unique indicator of volcanic sulfuric acid produced in the stratosphere and preserved in polar snow, and on the precise timing of the volcanic deposition in both polar regions, that another large eruption in 1809 of a volcano is also stratospheric and occurred in the tropics. The Tambora eruption and the undocumented 1809 eruption are together responsible for the unusually cold decade