HR: 08:00h
AN: GP41B-01 INVITED     [Abstracts]
TI: Fast changes in the geomagnetic dipole field intensity based on radionuclide records from ice cores
AU: * Muscheler, R
EM: raimund.muscheler@geol.lu.se
AF: Lund university / Quaternary Sciences, Soelvegatan 12 , Lund, 22362 Sweden
AU: Beer, J
EM: beer@eawag.ch
AF: EAWAG / ETH, Ueberlandstrasse 133, 8600, Duebendorf Switzerland
AU: Peter W., K
EM: kubik@phys.ethz.ch
AF: Paul Scherrer Institut / ETH , ETH Hoenggerberg / HPK H30, Zuerich, 8093 Switzerland
AU: Synal, H
EM: synal@particle.phys.ethz.ch
AF: Paul Scherrer Institut / ETH , ETH Hoenggerberg / HPK H30, Zuerich, 8093 Switzerland
AB: The production rates of cosmogenic radionuclides strongly depend on the geomagnetic shielding of the cosmic rays. Measuring cosmogenic radionuclides in natural archives, such as ice cores, allows the reconstruction of past changes in geomagnetic field intensity. Measurements of radionuclides in ice cores have the advantage to provide well-dated high-resolution records. Therefore, it is possible to study in detail short-term changes. Previous studies showed that 10Be and 36Cl records from Summit in central Greenland reliably record past changes in geomagnetic dipole field intensity. Around 40,000 yr BP these records show an increase in radionuclide deposition of approximately 100 % which corresponds to a geomagnetic minimum which is in the order of 10 % of the present field. This estimate refers to changes on time scales longer than 3000 years. During other periods there is similar variability on shorter time scales. For example, the so-called Mono Lake excursion is visible on time scales of 2000 years or shorter. Here, we will discuss 10Be and 36Cl records from the GRIP and GISP2 ice cores from Greenland. We will analyse the time evolution of the geomagnetic dipole field changes during the last ice age. In particular, the radionuclide changes and their time scales around the Laschamp and Mono Lake excursion will be discussed.
DE: 1513 Geomagnetic excursions
DE: 1521 Paleointensity
DE: 1522 Paleomagnetic secular variation
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting