Mathematics – Logic
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmos21d..12c&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #OS21D-12
Mathematics
Logic
4808 Chemical Tracers, 4860 Radioactivity And Radioisotopes
Scientific paper
The cosmogenic radionuclide 10Be is produced in the upper atmosphere by spallation of nitrogen and oxygen atoms. The production rate varies as a function of the flux of galactic cosmic rays (GCR) impinging on the Earth's atmosphere. On millennial time scale the GCR flux is modulated by the shielding of the Earth's magnetic field. Therefore deep sea sediments were suggested as archives for the reconstruction of the changes of the Earth's magnetic field in the pasta,b. However, a variation of the magnetic field is not the only factor influencing the 10Be record and there is still a debate about climatical influences on the 10Be depositional flux into deep sea sediments which could mask the production signalc.\In this work we want to quantify the factors influencing the depositional flux of 10Be into deep sea sediments such as: (i) sediment redistribution e.g. by bottom currents, (ii) enhanced boundary scavenging due to increased biological productivity at ocean boundaries, and (iii) changes of ocean circulation on glacial interglacial timescales. Whereas focusing and winnowing can be corrected for by normalizing to 230Thex, points (ii) and (iii) require model calculations. To simulate the depositional flux of 10Be and 230Th into deep sea sediments, a simple steady state two box model is usedd. The model results can be used to asses boundary scavenging intensity at a certain location and to correct the depositional flux of 10Be for transport processes. The adjusted 10Be records should contain only a production signal which is inversely related to the Earth's magnetic field intensity. On the one hand the model corrected 10Be records can be used to calculate relative variations of the Earth's magnetic field intensity. On the other hand, the model assumptions, regarding ocean circulation and bioproductivity, can be verified by comparing the model corrected 10Be records to the paleomagnetfield derived 10Be production changese. \ aLao, Y. et al.,1992, EPSL 113, 173-189. \bFrank, M. et al., 1997, EPSL 149, 121-129. \cKok, Y., 1999, EPSL 166, 105-119. \dAsmus, T. et al., 1999, Marine Geology 159, 63-78. \eGuyodo, Y. and Valet, J.P., 1996, EPSL 143, 23-36.
Christl Marcus
Kubik Peter W.
Mangini Augusto
Strobl C.
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