Ice layer dating

02-Nov-2014 01:20 by 6 Comments

Ice layer dating - dating site statistique

) that now extend back 800,000 years at Dome C and over 400,000 years at the Vostok site.Links are also provided to shorter records from other Antarctic locations.

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The original investigators made the effort to obtain the data and assure their quality.To assure proper credit is given, please follow the citation instructions in the headers of the data files and/or at the end of this page when using any of this material.If data accessed from this site are to be used in a publication, we strongly recommend some contact with the principal investigators to be sure the data are being interpreted and used correctly. Maps of Antarctica showing locations and elevations in meters above sea level (masl) of: Law Dome (66°44'S, 112°50'E, 1390 masl), Dome C (75°06'S, 123°24'E, 3233 masl), Taylor Dome (77°48'S, 158°43'E, 2365 masl), Vostok (78°28'S, 106°52'E, 3500 masl), Dome A (80°22'S, 77°22'E, 4084 masl), the South Pole station (90°S, 2810 masl), and Siple Station (75°55'S, 83°55'W, 1054 masl).Neither the principal investigators nor CDIAC is responsible for misuse of these data. At the Bern laboratory, four to six samples of approximately 8 grams from each depth level (0.55m intervals) in the ice core are crushed under vacuum conditions.The sample container is connected to a cold trap for several minutes to release air from the clathrates and the air is then expanded to a measuring cell where a laser measures absorption in a vibration–rotation transition line of the CO-in-air standard gas of 251.65 parts per million by volume (ppmv) scaled on the WMO mole fraction scale.At Grenoble (Laboratory of Glaciology, Geophysics and Environment) one to three ice samples of about 40 grams each are crushed under vacuum conditions, and after about 20 minutes the extracted gas is expanded in the sample loop of a gas chromatograph and analyzed.

Depending on the amount of extracted air, three to five successive analyses are done.To avoid possible effects of water-vapor interference, the CO) peak.Calibration is done using an Air Liquide standard scaled on CSIRO standards (172.8 ppmv, 260.3 ppmv, and 321.1 ppmv). given above if using the data in any published work.Uncertainty is a few ppmv; measurement error for the Bern laboratory is given in the data file, and the Grenoble Lab generally compares within a few ppmv for the common time interval. Over the last 800,000 years atmospheric CO levels as indicated by the ice-core data have fluctuated between 170 and 300 parts per million by volume (ppmv), corresponding with conditions of glacial and interglacial periods. Prior to about 450,000 years before present time (BP) atmospheric CO levels were always at or below 260 ppmv and reached lowest values, approaching 170 ppmv, between 660,000 and 670,000 years ago. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2008-055. Temporal uncertainty of the EPICA 800,000-year series increases with core depth, but estimates indicate that it is usually less than 5% of the true age and is frequently much less than that. The Vostok time scale is based on the the "GT4" chronology, derived in a similar fashion to "EDC3" with age constraints at 110 thousand and at 390 thousand years ago which are assumed to match known events in marine sediments. The highest pre-industrial value recorded in 800,000 years of ice-core record was 298.6 ppmv, in the Vostok core, around 330,000 years ago. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. (If accessing the data from this CDIAC site, please add: "accessed from the Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U. The most recent "EDC3" chronology is based on a snow accumulation and mechanical flow model combined with a set of independent age markers along the core, indicating either well-dated paleoclimatic records or insolation variations. Atmospheric CO levels have increased markedly in industrial times; measurements in year 2010 at Cape Grim Tasmania and the South Pole both indicated values of 386 ppmv, and are currently increasing at about 2 ppmv/year.

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