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

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..

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

Anomalous sulfur isotope compositions of volcanic sulfate over the last millennium in Antarctic ice cores

International audienceThe reconstruction of past volcanism from glaciological archives is based on the measurement of sulfate concentrations in ice. This method does not allow a proper evaluation of the climatic impact of an eruption owing to the uncertainty in classifying an event between stratospheric or tropospheric. This work develops a new method, using anomalous sulfur isotope composition of volcanic sulfate in order to identify stratospheric eruptions over the last millennium. The advantages and limits of this new method are established with the examination of the 10 largest volcanic signals in ice cores from Dome C and South Pole, Antarctica. Of the 10, seven are identified as stratospheric eruptions. Among them, three have been known to be stratospheric (Tambora, Kuwae, the 1259 Unknown Event) and they exhibit anomalous sulfur isotope compositions. Three unknown events (circa 1277, 1230, 1170 A.D.) and the Serua eruption have been identified as stratospheric eruptions, which suggests for the first time that they could have had significant climatic impact. However, the Kuwae and the 1259 Unknown Event stratospheric eruptions exhibit different anomalous sulfur isotope compositions between South Pole and Dome C samples. Differences in sulfate deposition and preservation patterns between the two sites can help explain these discrepancies. This study shows that the presence of an anomalous sulfur isotope composition of volcanic sulfate in ice core indicates a stratospheric eruption, but the absence of such composition does not necessarily lead to the conclusion of a tropospheric process because of differences in the sulfate deposition on the ice sheet

Design and performance of an automated chemical extraction bench for the preparation of 10Be and 26Al targets to be analyzed by accelerator mass spectrometry

International audienceThe growing number of studies based on data provided by the accelerator mass spectrometry (AMS) technique from increasingly diverse matrices implies that developing very effective and reproducible sample processing techniques is crucial to meet the demand generated. After being dissolved, the isolation of the cosmogenic nuclide to be measured and its chemical purification imply complex processes throughout successive stages The presented automatic system was designed to perform the final steps of the Be-10 and Al-26 chemical extraction protocol from natural matrices (sediments, pure mineral phases, ...), previously purified, decontaminated and dissolved in the case of in situ-produced cosmogenic nuclides, or leached or dissolved in the case of meteoric cosmogenic nuclides. Driven by Labview software, the developed automatic system, in addition to freeing the operator from tedious tasks, allows reproducibly processing simultaneously up to eight samples of different volumes in roughly 40 min. This article presents the design of the automated extraction bench and its performance based on the recovery efficiency of the stable element and the reproducibility of the measurements of the cosmogenic nuclide concentrations by AMS

A Multi-isotope Composite Record of Solar Activity and Irradiance Reconstruction over the last 9000 Years

International audienc