HR: 08:00h
AN: GP41A-02    [Abstracts]
TI: On the Expression of the 41,000 year in the Paleomagnetic Record of the Geomagnetic Field.
AU: * Fuller, M
EM: mfuller@soest.hawaii.edu
AF: HIGP-SOEST, University of Hawai, Honolulu, HI 96822, United States
AB: Several authors have suggested that there is expression of the obliquity period in the paleomagnetic record, implying a role for precession in driving the dynamo. However, the observation remains controversial. The power at 41,000 years is only weak. Yet, it does appear that (1) excursions and major intensity lows are associated with minima in the obliquity signal during the last 800 kyrs (2) the distribution of the length of events less than 100,000 years peaks at 30 - 40,000 years. i.e. a little shorter than the obliquity cycle (3) reversals preferentially occur when the amplitude of the obliquity signal is low in the past 5 Myrs. (4) reversals occur preferentially within the obliquity cycle close to the point of inflection in the decrease from the maximum value. These observations have been rexamined using additional data, which extend the time scale of the tests. Particular emphasis is placed on the phase relationship of the obliquity cycle and the onset of reversals and excursions. The results are consistent with the earlier suggestion that there is expression of the 41,000yr obliquity cycle in the paleomagnetic record. Thus precession may play a role in driving the dynamo. However, possible relative motion between core and mantle due to changes in surface mass distribution, which are caused by climatic changes, may also occur. Preliminary results indicate that for the last 800 Kyr there is no strong systematic relationship between magnetic intensity lows and the del 18 O record, or ice record.
DE: 1507 Core processes (1213, 8115)
DE: 1521 Paleointensity
DE: 1522 Paleomagnetic secular variation
DE: 1535 Reversals: process, timescale, magnetostratigraphy
DE: 1560 Time variations: secular and longer
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly