HR: 0800h
AN: PP11A-0543    [Abstracts]
TI: Isotopic Constraints on the Neogene Flow of Northern Component Water
AU: * Poore, H R
EM: poore@esc.cam.ac.uk
AF: Bullard Laboratory, Department of Earth Sciences, University of Cambridge, Madingley Rd., Cambridge., CB3 OEZ United Kingdom
AU: Crowhurst, S J
AF: Godwin Institute for Quaternary Research, University of Cambridge, New Museums Site, Pembroke St., Cambridge., CB2 3SA United Kingdom
AU: Jones, S M
AF: Department of Geology, University of Dublin, Trinity College, College Green, Dublin, 2 Ireland
AU: McCave, I N
AF: Godwin Institute for Quaternary Research, University of Cambridge, New Museums Site, Pembroke St., Cambridge., CB2 3SA United Kingdom
AU: Pfuhl, H
AF: Godwin Institute for Quaternary Research, University of Cambridge, New Museums Site, Pembroke St., Cambridge., CB2 3SA United Kingdom
AU: Samworth, R J
AF: Statistical Laboratory, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Rd., Cambridge., CB3 OWB United Kingdom
AU: White, N
AF: Bullard Laboratory, Department of Earth Sciences, University of Cambridge, Madingley Rd., Cambridge., CB3 OEZ United Kingdom
AB: Benthic foraminiferal isotope data have been assembled to examine Neogene $\delta^{13}$C gradients between the major ocean basins. These data are reported on the astronomical time scale of Lourens et al. (2004) and correlated to high resolution benthic $\delta^{18}$O records, resulting in a higher precision of correlation between cores. A local linear kernel regression procedure (i.e. a type of nonparametric regression) is used to produce a regional estimate of $\delta^{13}$C in each of the North Atlantic, Southern and Pacific Oceans. Confidence bands for the regression estimates are found through both analytic and bootstrap techniques and a simulation extrapolation procedure is applied to understand the effect of errors in age determinations. Estimated uncertainties are used to establish the value of interbasinal $\delta^{13}$C gradients as a tool for Neogene paleoceanographic reconstructions. Uncertainties in carbon isotope measurements are considerably larger than instrument error: it is mostly a result of sample variance, comprising variable vital effect corrections, diagenesis, etc. During intervals of reduced $\delta^{13}$C gradients, the uncertainties are such that the use of carbon isotope techniques in understanding paleoceanographic circulation patterns is severely limited. Confidence bands overlap for much of the Neogene period, and $\delta^{13}$C values diverge only in the last 8 Ma. Interpretation of $\delta^{13}$C gradients before 8 Ma is particularly troublesome. Possible causes for changes in the influence of northern-derived Northern Component Water (NCW) in the Southern Ocean are examined. We assess the importance of mantle-plume control of the northern gateway around Iceland. Temperature fluctuations of mantle-plume material beneath the region cause changes in the bathymetry of the Greenland-Scotland Ridge, and are believed to be a contributing factor to fluctuations in %NCW throughout the Neogene period. Lourens et al. 2004. The Neogene Period. In F.M. Gradstein, J.G.Ogg, A.G. Smith et al. - A Geologic Time Scale 2004. Cambridge University Press, UK.
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 4870 Stable isotopes
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting