HR: 10:50h
AN: U42A-03    [Abstracts]
TI: A new Counted Greenland ice Core Chronology (GICC05)
AU: * Steffensen, J P
EM: jps@gfy.ku.dk
AF: niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Copenhagen O, DK-2100 Denmark
AB: During a five year grant the Ice and Climate group at Niels Bohr Institute, University of Copenhagen is performing annual layer counts in the Dye-3, GRIP and NGRIP ice cores to obtain a Greenland ice core chronology on past climatic and environmental events. The counting is based on seasonal variations in stable isotopes, in chemical impurities and dust and in visual stratigraphy. Using ash layers and acid layers from major volcanic eruptions as primary stratigraphic fixpoints and acid layers from smaller volcanoes as secondary fixpoints, the three ice core records have been stratigraphically "inter locked". This has allowed for a compilation of the three chronologies into one. I will present the new Greenland Ice core Chronology which until now extends back to 40,000 years B.P. This chronology provides dates on a number of abrupt climate changes, on a number of volcanic tephra layers and on variations in atmospheric concentrations of 10Beryllium. It will thus be possible to link the Greenland ice core chronology to marine sediment records, to terrestrial records, to dendrochronologies and the Carbon-14 calibration curve. Although a certain counting uncertainty remains and the dating of deep ice strata will be influenced by this, the new chronology offers very precise differential dating possibilities. It is possible to track the abrupt climate changes on a year by year basis and the age difference between such transitions and e.g. a volcanic eruption from the same period can be determined with uncertainties of a few years. Since a row of different parameters have been measured at high resolution in the NGRIP ice core it has been possible to obtain a picture of the dynamics across abrupt climate changes. The data allows us to determine the termination of the Younger Dryas within less than 5 years.
DE: 1105 Quaternary geochronology
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4932 Ice cores (0724)
DE: 8408 Volcano/climate interactions (1605, 3309)
SC: Union [U]
MN: Fall Meeting 2005