HR: 13:55h
AN: OS13A-02 INVITED     [Abstracts]
TI: Paleo-ocean chemistry based on records in marine sedimentary opal: implications for effect of Fe and other trace elements on biological productivity
AU: * Lal, D
EM: dlal@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0244 United States
AU: Charles, C D
EM: ccharles@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0244 United States
AU: Vacher, L
EM: lvacher@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0244 United States
AU: Jull, A J
EM: jull@u.arizona.edu
AF: University of Arizona, NSF AMS Facility, Tucson, AZ 85721 United States
AU: McHargue, L
EM: mchargue@physics.Arizona.EDU
AF: University of Arizona, NSF AMS Facility, Tucson, AZ 85721 United States
AB: We report on our discovery that marine opal contains a high fidelity record of dissolved oceanic concentrations of cosmic ray-produced radionuclides, ¹⁰Be and ²⁶Al, while also capturing temporal variations in a large number of trace elements such as Ti, Fe, Zn, and Mn. This finding is based on our studies of trace elements (and two cosmogenic nuclides) in biogenic opal, over the last full ice age cycle, in opal derived from the site 1093 and its companion piston core TN057-13 (49^o 59^'S, 5^o 52^'E), near the present-day position of the Antarctic Polar Front. The data show potential for determining the controls on global ocean productivity -- in particular, the extent to which marine production can be modulated by external sources of micronutrients. Despite clear evidence for iron limitation in the modern ocean, the sedimentary record of "paleoproductivity" has not as yet offered any clear picture of the possible relationship between the changes in dust flux (known to have occurred over ice age cycles, for example), and regional or global productivity. Thus, with one sedimentary phase and in single sedimentary sections, we now have the potential to compare directly a proxy for aeolian input of micronutrients (e.g. Fe or Ti), with a proxy for production (e.g. ²⁶Al/Al ratios). We expect that studies of the temporal records of trace elements and cosmogenic nuclides in contrasting regions of upwelling and productivity, which exhibit different sensitivities to global climate fluctuations and micronutrient inputs, would lead to a direct and comprehensive test of ideas such as Martin's hypothesis of iron control of atmospheric carbon dioxide Martin (1990), in different oceanic provinces during glacial cycles. Reference: Martin, J.H. Glacial-interglacial CO2 change: the iron hypothesis. Paleoceanography 5, 1-13, 1990.
DE: 4200 OCEANOGRAPHY: GENERAL
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly